diff options
author | Eliot Horowitz <eliot@10gen.com> | 2014-11-04 15:46:40 -0500 |
---|---|---|
committer | Eliot Horowitz <eliot@10gen.com> | 2014-11-05 11:21:19 -0500 |
commit | 5ca2daf551a2c631a5f573cb054406f5d49fbef5 (patch) | |
tree | b0a23d34ffdb376bac0b79ed17b5619cfc0d9b47 /src/third_party/wiredtiger/src/btree/bt_slvg.c | |
parent | 017704acdfc7517efadb3fab167bba06c025c01a (diff) | |
download | mongo-5ca2daf551a2c631a5f573cb054406f5d49fbef5.tar.gz |
SERVER-15953: add wiredtiger to third_party
Diffstat (limited to 'src/third_party/wiredtiger/src/btree/bt_slvg.c')
-rw-r--r-- | src/third_party/wiredtiger/src/btree/bt_slvg.c | 2520 |
1 files changed, 2520 insertions, 0 deletions
diff --git a/src/third_party/wiredtiger/src/btree/bt_slvg.c b/src/third_party/wiredtiger/src/btree/bt_slvg.c new file mode 100644 index 00000000000..10366e91a0e --- /dev/null +++ b/src/third_party/wiredtiger/src/btree/bt_slvg.c @@ -0,0 +1,2520 @@ +/*- + * Copyright (c) 2008-2014 WiredTiger, Inc. + * All rights reserved. + * + * See the file LICENSE for redistribution information. + */ + +#include "wt_internal.h" + +struct __wt_stuff; typedef struct __wt_stuff WT_STUFF; +struct __wt_track; typedef struct __wt_track WT_TRACK; +struct __wt_track_shared; typedef struct __wt_track_shared WT_TRACK_SHARED; + +/* + * There's a bunch of stuff we pass around during salvage, group it together + * to make the code prettier. + */ +struct __wt_stuff { + WT_SESSION_IMPL *session; /* Salvage session */ + + WT_TRACK **pages; /* Pages */ + uint32_t pages_next; /* Next empty slot */ + size_t pages_allocated; /* Bytes allocated */ + + WT_TRACK **ovfl; /* Overflow pages */ + uint32_t ovfl_next; /* Next empty slot */ + size_t ovfl_allocated; /* Bytes allocated */ + + WT_REF root_ref; /* Created root page */ + + uint8_t page_type; /* Page type */ + + /* If need to free blocks backing merged page ranges. */ + int merge_free; + + WT_ITEM *tmp1; /* Verbose print buffer */ + WT_ITEM *tmp2; /* Verbose print buffer */ + + uint64_t fcnt; /* Progress counter */ +}; + +/* + * WT_TRACK_SHARED -- + * Information shared between pages being merged. + */ +struct __wt_track_shared { + uint32_t ref; /* Reference count */ + + /* + * Physical information about the file block. + */ + WT_ADDR addr; /* Page address */ + uint32_t size; /* Page size */ + uint64_t gen; /* Page generation */ + + /* + * Pages that reference overflow pages contain a list of the overflow + * pages they reference. We start out with a list of addresses, and + * convert to overflow array slots during the reconciliation of page + * references to overflow records. + */ + WT_ADDR *ovfl_addr; /* Overflow pages by address */ + uint32_t *ovfl_slot; /* Overflow pages by slot */ + uint32_t ovfl_cnt; /* Overflow reference count */ +}; + +/* + * WT_TRACK -- + * Structure to track chunks, one per chunk; we start out with a chunk per + * page (either leaf or overflow), but when we find overlapping key ranges, we + * split the leaf page chunks up, one chunk for each unique key range. + */ +struct __wt_track { +#define trk_addr shared->addr.addr +#define trk_addr_size shared->addr.size +#define trk_gen shared->gen +#define trk_ovfl_addr shared->ovfl_addr +#define trk_ovfl_cnt shared->ovfl_cnt +#define trk_ovfl_slot shared->ovfl_slot +#define trk_size shared->size + WT_TRACK_SHARED *shared; /* Shared information */ + + WT_STUFF *ss; /* Enclosing stuff */ + + union { + struct { +#undef row_start +#define row_start u.row._row_start + WT_ITEM _row_start; /* Row-store start range */ +#undef row_stop +#define row_stop u.row._row_stop + WT_ITEM _row_stop; /* Row-store stop range */ + } row; + + struct { +#undef col_start +#define col_start u.col._col_start + uint64_t _col_start; /* Col-store start range */ +#undef col_stop +#define col_stop u.col._col_stop + uint64_t _col_stop; /* Col-store stop range */ +#undef col_missing +#define col_missing u.col._col_missing + uint64_t _col_missing; /* Col-store missing range */ + } col; + } u; + +#define WT_TRACK_CHECK_START 0x01 /* Row: initial key updated */ +#define WT_TRACK_CHECK_STOP 0x02 /* Row: last key updated */ +#define WT_TRACK_MERGE 0x04 /* Page requires merging */ +#define WT_TRACK_OVFL_REFD 0x08 /* Overflow page referenced */ + u_int flags; +}; + +static int __slvg_cleanup(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_col_build_internal(WT_SESSION_IMPL *, uint32_t, WT_STUFF *); +static int __slvg_col_build_leaf(WT_SESSION_IMPL *, WT_TRACK *, WT_REF *); +static int __slvg_col_ovfl( + WT_SESSION_IMPL *, WT_TRACK *, WT_PAGE *, uint64_t, uint64_t); +static int __slvg_col_range(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_col_range_missing(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_col_range_overlap( + WT_SESSION_IMPL *, uint32_t, uint32_t, WT_STUFF *); +static void __slvg_col_trk_update_start(uint32_t, WT_STUFF *); +static int __slvg_merge_block_free(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_ovfl_compare(const void *, const void *); +static int __slvg_ovfl_discard(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_ovfl_reconcile(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_ovfl_ref(WT_SESSION_IMPL *, WT_TRACK *, int); +static int __slvg_ovfl_ref_all(WT_SESSION_IMPL *, WT_TRACK *); +static int __slvg_read(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_row_build_internal(WT_SESSION_IMPL *, uint32_t, WT_STUFF *); +static int __slvg_row_build_leaf( + WT_SESSION_IMPL *, WT_TRACK *, WT_REF *, WT_STUFF *); +static int __slvg_row_ovfl( + WT_SESSION_IMPL *, WT_TRACK *, WT_PAGE *, uint32_t, uint32_t); +static int __slvg_row_range(WT_SESSION_IMPL *, WT_STUFF *); +static int __slvg_row_range_overlap( + WT_SESSION_IMPL *, uint32_t, uint32_t, WT_STUFF *); +static int __slvg_row_trk_update_start( + WT_SESSION_IMPL *, WT_ITEM *, uint32_t, WT_STUFF *); +static int __slvg_trk_compare_addr(const void *, const void *); +static int __slvg_trk_compare_gen(const void *, const void *); +static int __slvg_trk_compare_key(const void *, const void *); +static int __slvg_trk_free(WT_SESSION_IMPL *, WT_TRACK **, int); +static void __slvg_trk_free_addr(WT_SESSION_IMPL *, WT_TRACK *); +static int __slvg_trk_init(WT_SESSION_IMPL *, uint8_t *, + size_t, uint32_t, uint64_t, WT_STUFF *, WT_TRACK **); +static int __slvg_trk_leaf(WT_SESSION_IMPL *, + const WT_PAGE_HEADER *, uint8_t *, size_t, WT_STUFF *); +static int __slvg_trk_leaf_ovfl( + WT_SESSION_IMPL *, const WT_PAGE_HEADER *, WT_TRACK *); +static int __slvg_trk_ovfl(WT_SESSION_IMPL *, + const WT_PAGE_HEADER *, uint8_t *, size_t, WT_STUFF *); +static int __slvg_trk_split(WT_SESSION_IMPL *, WT_TRACK *, WT_TRACK **); + +/* + * __wt_bt_salvage -- + * Salvage a Btree. + */ +int +__wt_bt_salvage(WT_SESSION_IMPL *session, WT_CKPT *ckptbase, const char *cfg[]) +{ + WT_BM *bm; + WT_BTREE *btree; + WT_DECL_RET; + WT_STUFF *ss, stuff; + uint32_t i, leaf_cnt; + + WT_UNUSED(cfg); + + btree = S2BT(session); + bm = btree->bm; + + WT_CLEAR(stuff); + ss = &stuff; + ss->session = session; + ss->page_type = WT_PAGE_INVALID; + + /* Allocate temporary buffers. */ + WT_ERR(__wt_scr_alloc(session, 0, &ss->tmp1)); + WT_ERR(__wt_scr_alloc(session, 0, &ss->tmp2)); + + /* + * Step 1: + * Inform the underlying block manager that we're salvaging the file. + */ + WT_ERR(bm->salvage_start(bm, session)); + + /* + * Step 2: + * Read the file and build in-memory structures that reference any leaf + * or overflow page. Any pages other than leaf or overflow pages are + * added to the free list. + * + * Turn off read checksum and verification error messages while we're + * reading the file, we expect to see corrupted blocks. + */ + F_SET(session, WT_SESSION_SALVAGE_CORRUPT_OK); + ret = __slvg_read(session, ss); + F_CLR(session, WT_SESSION_SALVAGE_CORRUPT_OK); + WT_ERR(ret); + + /* + * Step 3: + * Discard any page referencing a non-existent overflow page. We do + * this before checking overlapping key ranges on the grounds that a + * bad key range we can use is better than a terrific key range that + * references pages we don't have. On the other hand, we subsequently + * discard key ranges where there are better overlapping ranges, and + * it would be better if we let the availability of an overflow value + * inform our choices as to the key ranges we select, ideally on a + * per-key basis. + * + * A complicating problem is found in variable-length column-store + * objects, where we potentially split key ranges within RLE units. + * For example, if there's a page with rows 15-20 and we later find + * row 17 with a larger LSN, the range splits into 3 chunks, 15-16, + * 17, and 18-20. If rows 15-20 were originally a single value (an + * RLE of 6), and that record is an overflow record, we end up with + * two chunks, both of which want to reference the same overflow value. + * + * Instead of the approach just described, we're first discarding any + * pages referencing non-existent overflow pages, then we're reviewing + * our key ranges and discarding any that overlap. We're doing it that + * way for a few reasons: absent corruption, missing overflow items are + * strong arguments the page was replaced (on the other hand, some kind + * of file corruption is probably why we're here); it's a significant + * amount of additional complexity to simultaneously juggle overlapping + * ranges and missing overflow items; finally, real-world applications + * usually don't have a lot of overflow items, as WiredTiger supports + * very large page sizes, overflow items shouldn't be common. + * + * Step 4: + * Add unreferenced overflow page blocks to the free list so they are + * reused immediately. + */ + if (ss->ovfl_next != 0) { + WT_ERR(__slvg_ovfl_reconcile(session, ss)); + WT_ERR(__slvg_ovfl_discard(session, ss)); + } + + /* + * Step 5: + * Walk the list of pages looking for overlapping ranges to resolve. + * If we find a range that needs to be resolved, set a global flag + * and a per WT_TRACK flag on the pages requiring modification. + * + * This requires sorting the page list by key, and secondarily by LSN. + * + * !!! + * It's vanishingly unlikely and probably impossible for fixed-length + * column-store files to have overlapping key ranges. It's possible + * for an entire key range to go missing (if a page is corrupted and + * lost), but because pages can't split, it shouldn't be possible to + * find pages where the key ranges overlap. That said, we check for + * it and clean up after it in reconciliation because it doesn't cost + * much and future column-store formats or operations might allow for + * fixed-length format ranges to overlap during salvage, and I don't + * want to have to retrofit the code later. + */ + qsort(ss->pages, + (size_t)ss->pages_next, sizeof(WT_TRACK *), __slvg_trk_compare_key); + if (ss->page_type == WT_PAGE_ROW_LEAF) + WT_ERR(__slvg_row_range(session, ss)); + else + WT_ERR(__slvg_col_range(session, ss)); + + /* + * Step 6: + * We may have lost key ranges in column-store databases, that is, some + * part of the record number space is gone. Look for missing ranges. + */ + switch (ss->page_type) { + case WT_PAGE_COL_FIX: + case WT_PAGE_COL_VAR: + WT_ERR(__slvg_col_range_missing(session, ss)); + break; + case WT_PAGE_ROW_LEAF: + break; + } + + /* + * Step 7: + * Build an internal page that references all of the leaf pages, + * and write it, as well as any merged pages, to the file. + * + * Count how many leaf pages we have (we could track this during the + * array shuffling/splitting, but that's a lot harder). + */ + for (leaf_cnt = i = 0; i < ss->pages_next; ++i) + if (ss->pages[i] != NULL) + ++leaf_cnt; + if (leaf_cnt != 0) + switch (ss->page_type) { + case WT_PAGE_COL_FIX: + case WT_PAGE_COL_VAR: + WT_ERR( + __slvg_col_build_internal(session, leaf_cnt, ss)); + break; + case WT_PAGE_ROW_LEAF: + WT_ERR( + __slvg_row_build_internal(session, leaf_cnt, ss)); + break; + } + + /* + * Step 8: + * If we had to merge key ranges, we have to do a final pass through + * the leaf page array and discard file pages used during key merges. + * We can't do it earlier: if we free'd the leaf pages we're merging as + * we merged them, the write of subsequent leaf pages or the internal + * page might allocate those free'd file blocks, and if the salvage run + * subsequently fails, we'd have overwritten pages used to construct the + * final key range. In other words, if the salvage run fails, we don't + * want to overwrite data the next salvage run might need. + */ + if (ss->merge_free) + WT_ERR(__slvg_merge_block_free(session, ss)); + + /* + * Step 9: + * Evict the newly created root page, creating a checkpoint. + */ + if (ss->root_ref.page != NULL) { + btree->ckpt = ckptbase; + ret = __wt_rec_evict(session, &ss->root_ref, 1); + ss->root_ref.page = NULL; + btree->ckpt = NULL; + } + + /* + * Step 10: + * Inform the underlying block manager that we're done. + */ +err: WT_TRET(bm->salvage_end(bm, session)); + + /* Discard any root page we created. */ + if (ss->root_ref.page != NULL) + __wt_ref_out(session, &ss->root_ref); + + /* Discard the leaf and overflow page memory. */ + WT_TRET(__slvg_cleanup(session, ss)); + + /* Discard temporary buffers. */ + __wt_scr_free(&ss->tmp1); + __wt_scr_free(&ss->tmp2); + + /* Wrap up reporting. */ + WT_TRET(__wt_progress(session, NULL, ss->fcnt)); + + return (ret); +} + +/* + * __slvg_read -- + * Read the file and build a table of the pages we can use. + */ +static int +__slvg_read(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_BM *bm; + WT_DECL_ITEM(as); + WT_DECL_ITEM(buf); + WT_DECL_RET; + const WT_PAGE_HEADER *dsk; + size_t addr_size; + uint8_t addr[WT_BTREE_MAX_ADDR_COOKIE]; + int eof, valid; + + bm = S2BT(session)->bm; + WT_ERR(__wt_scr_alloc(session, 0, &as)); + WT_ERR(__wt_scr_alloc(session, 0, &buf)); + + for (;;) { + /* Get the next block address from the block manager. */ + WT_ERR(bm->salvage_next(bm, session, addr, &addr_size, &eof)); + if (eof) + break; + + /* Report progress every 10 chunks. */ + if (++ss->fcnt % 10 == 0) + WT_ERR(__wt_progress(session, NULL, ss->fcnt)); + + /* + * Read (and potentially decompress) the block; the underlying + * block manager might return only good blocks if checksums are + * configured, or both good and bad blocks if we're relying on + * compression. + * + * Report the block's status to the block manager. + */ + if ((ret = __wt_bt_read(session, buf, addr, addr_size)) == 0) + valid = 1; + else { + valid = 0; + if (ret == WT_ERROR) + ret = 0; + WT_ERR(ret); + } + WT_ERR(bm->salvage_valid(bm, session, addr, addr_size, valid)); + if (!valid) + continue; + + /* Create a printable version of the address. */ + WT_ERR(bm->addr_string(bm, session, as, addr, addr_size)); + + /* + * Make sure it's an expected page type for the file. + * + * We only care about leaf and overflow pages from here on out; + * discard all of the others. We put them on the free list now, + * because we might as well overwrite them, we want the file to + * grow as little as possible, or shrink, and future salvage + * calls don't need them either. + */ + dsk = buf->data; + switch (dsk->type) { + case WT_PAGE_BLOCK_MANAGER: + case WT_PAGE_COL_INT: + case WT_PAGE_ROW_INT: + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s page ignored %s", + __wt_page_type_string(dsk->type), + (const char *)as->data)); + WT_ERR(bm->free(bm, session, addr, addr_size)); + continue; + } + + /* + * Verify the page. It's unlikely a page could have a valid + * checksum and still be broken, but paranoia is healthy in + * salvage. Regardless, verify does return failure because + * it detects failures we'd expect to see in a corrupted file, + * like overflow references past the end of the file or + * overflow references to non-existent pages, might as well + * discard these pages now. + */ + if (__wt_verify_dsk(session, as->data, buf) != 0) { + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s page failed verify %s", + __wt_page_type_string(dsk->type), + (const char *)as->data)); + WT_ERR(bm->free(bm, session, addr, addr_size)); + continue; + } + + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "tracking %s page, generation %" PRIu64 " %s", + __wt_page_type_string(dsk->type), dsk->write_gen, + (const char *)as->data)); + + switch (dsk->type) { + case WT_PAGE_COL_FIX: + case WT_PAGE_COL_VAR: + case WT_PAGE_ROW_LEAF: + if (ss->page_type == WT_PAGE_INVALID) + ss->page_type = dsk->type; + if (ss->page_type != dsk->type) + WT_ERR_MSG(session, WT_ERROR, + "file contains multiple file formats (both " + "%s and %s), and cannot be salvaged", + __wt_page_type_string(ss->page_type), + __wt_page_type_string(dsk->type)); + + WT_ERR(__slvg_trk_leaf( + session, dsk, addr, addr_size, ss)); + break; + case WT_PAGE_OVFL: + WT_ERR(__slvg_trk_ovfl( + session, dsk, addr, addr_size, ss)); + break; + } + } + +err: __wt_scr_free(&as); + __wt_scr_free(&buf); + + return (ret); +} + +/* + * __slvg_trk_init -- + * Initialize tracking information for a page. + */ +static int +__slvg_trk_init(WT_SESSION_IMPL *session, + uint8_t *addr, size_t addr_size, + uint32_t size, uint64_t gen, WT_STUFF *ss, WT_TRACK **retp) +{ + WT_DECL_RET; + WT_TRACK *trk; + + WT_RET(__wt_calloc_def(session, 1, &trk)); + WT_ERR(__wt_calloc_def(session, 1, &trk->shared)); + trk->shared->ref = 1; + + trk->ss = ss; + WT_ERR(__wt_strndup(session, addr, addr_size, &trk->trk_addr)); + trk->trk_addr_size = (uint8_t)addr_size; + trk->trk_size = size; + trk->trk_gen = gen; + + *retp = trk; + return (0); + +err: __wt_free(session, trk->trk_addr); + __wt_free(session, trk->shared); + __wt_free(session, trk); + return (ret); +} + +/* + * __slvg_trk_split -- + * Split a tracked chunk. + */ +static int +__slvg_trk_split(WT_SESSION_IMPL *session, WT_TRACK *orig, WT_TRACK **newp) +{ + WT_TRACK *trk; + + WT_RET(__wt_calloc_def(session, 1, &trk)); + + trk->shared = orig->shared; + trk->ss = orig->ss; + + ++orig->shared->ref; + + *newp = trk; + return (0); +} + +/* + * __slvg_trk_leaf -- + * Track a leaf page. + */ +static int +__slvg_trk_leaf(WT_SESSION_IMPL *session, + const WT_PAGE_HEADER *dsk, uint8_t *addr, size_t addr_size, WT_STUFF *ss) +{ + WT_BTREE *btree; + WT_CELL *cell; + WT_CELL_UNPACK *unpack, _unpack; + WT_DECL_RET; + WT_PAGE *page; + WT_TRACK *trk; + uint64_t stop_recno; + uint32_t i; + + btree = S2BT(session); + unpack = &_unpack; + page = NULL; + trk = NULL; + + /* Re-allocate the array of pages, as necessary. */ + WT_RET(__wt_realloc_def( + session, &ss->pages_allocated, ss->pages_next + 1, &ss->pages)); + + /* Allocate a WT_TRACK entry for this new page and fill it in. */ + WT_RET(__slvg_trk_init( + session, addr, addr_size, dsk->mem_size, dsk->write_gen, ss, &trk)); + + switch (dsk->type) { + case WT_PAGE_COL_FIX: + /* + * Column-store fixed-sized format: start and stop keys can be + * taken from the block's header, and doesn't contain overflow + * items. + */ + trk->col_start = dsk->recno; + trk->col_stop = dsk->recno + (dsk->u.entries - 1); + + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s records %" PRIu64 "-%" PRIu64, + __wt_addr_string( + session, trk->trk_addr, trk->trk_addr_size, ss->tmp1), + trk->col_start, trk->col_stop)); + break; + case WT_PAGE_COL_VAR: + /* + * Column-store variable-length format: the start key can be + * taken from the block's header, stop key requires walking + * the page. + */ + stop_recno = dsk->recno; + WT_CELL_FOREACH(btree, dsk, cell, unpack, i) { + __wt_cell_unpack(cell, unpack); + stop_recno += __wt_cell_rle(unpack); + } + + trk->col_start = dsk->recno; + trk->col_stop = stop_recno - 1; + + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s records %" PRIu64 "-%" PRIu64, + __wt_addr_string( + session, trk->trk_addr, trk->trk_addr_size, ss->tmp1), + trk->col_start, trk->col_stop)); + + /* Column-store pages can contain overflow items. */ + WT_ERR(__slvg_trk_leaf_ovfl(session, dsk, trk)); + break; + case WT_PAGE_ROW_LEAF: + /* + * Row-store format: copy the first and last keys on the page. + * Keys are prefix-compressed, the simplest and slowest thing + * to do is instantiate the in-memory page, then instantiate + * and copy the full keys, then free the page. We do this + * on every leaf page, and if you need to speed up the salvage, + * it's probably a great place to start. + */ + WT_ERR(__wt_page_inmem(session, NULL, dsk, 0, &page)); + WT_ERR(__wt_row_leaf_key_copy(session, + page, &page->pg_row_d[0], &trk->row_start)); + WT_ERR(__wt_row_leaf_key_copy(session, page, + &page->pg_row_d[page->pg_row_entries - 1], &trk->row_stop)); + + if (WT_VERBOSE_ISSET(session, WT_VERB_SALVAGE)) { + WT_ERR(__wt_buf_set_printable(session, ss->tmp1, + trk->row_start.data, trk->row_start.size)); + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s start key %.*s", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, ss->tmp2), + (int)ss->tmp1->size, (char *)ss->tmp1->data)); + WT_ERR(__wt_buf_set_printable(session, ss->tmp1, + trk->row_stop.data, trk->row_stop.size)); + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s stop key %.*s", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, ss->tmp2), + (int)ss->tmp1->size, (char *)ss->tmp1->data)); + } + + /* Row-store pages can contain overflow items. */ + WT_ERR(__slvg_trk_leaf_ovfl(session, dsk, trk)); + break; + } + ss->pages[ss->pages_next++] = trk; + + if (0) { +err: __wt_free(session, trk); + } + if (page != NULL) + __wt_page_out(session, &page); + return (ret); +} + +/* + * __slvg_trk_ovfl -- + * Track an overflow page. + */ +static int +__slvg_trk_ovfl(WT_SESSION_IMPL *session, + const WT_PAGE_HEADER *dsk, uint8_t *addr, size_t addr_size, WT_STUFF *ss) +{ + WT_TRACK *trk; + + /* + * Reallocate the overflow page array as necessary, then save the + * page's location information. + */ + WT_RET(__wt_realloc_def( + session, &ss->ovfl_allocated, ss->ovfl_next + 1, &ss->ovfl)); + + WT_RET(__slvg_trk_init( + session, addr, addr_size, dsk->mem_size, dsk->write_gen, ss, &trk)); + ss->ovfl[ss->ovfl_next++] = trk; + + return (0); +} + +/* + * __slvg_trk_leaf_ovfl -- + * Search a leaf page for overflow items. + */ +static int +__slvg_trk_leaf_ovfl( + WT_SESSION_IMPL *session, const WT_PAGE_HEADER *dsk, WT_TRACK *trk) +{ + WT_BTREE *btree; + WT_CELL *cell; + WT_CELL_UNPACK *unpack, _unpack; + uint32_t i, ovfl_cnt; + + btree = S2BT(session); + unpack = &_unpack; + + /* + * Two passes: count the overflow items, then copy them into an + * allocated array. + */ + ovfl_cnt = 0; + WT_CELL_FOREACH(btree, dsk, cell, unpack, i) { + __wt_cell_unpack(cell, unpack); + if (unpack->ovfl) + ++ovfl_cnt; + } + if (ovfl_cnt == 0) + return (0); + + /* Allocate room for the array of overflow addresses and fill it in. */ + WT_RET(__wt_calloc_def(session, ovfl_cnt, &trk->trk_ovfl_addr)); + trk->trk_ovfl_cnt = ovfl_cnt; + + ovfl_cnt = 0; + WT_CELL_FOREACH(btree, dsk, cell, unpack, i) { + __wt_cell_unpack(cell, unpack); + if (unpack->ovfl) { + WT_RET(__wt_strndup(session, unpack->data, + unpack->size, &trk->trk_ovfl_addr[ovfl_cnt].addr)); + trk->trk_ovfl_addr[ovfl_cnt].size = + (uint8_t)unpack->size; + + WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s overflow reference %s", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1), + __wt_addr_string(session, + unpack->data, unpack->size, trk->ss->tmp2))); + + if (++ovfl_cnt == trk->trk_ovfl_cnt) + break; + } + } + + return (0); +} + +/* + * __slvg_col_range -- + * Figure out the leaf pages we need and free the leaf pages we don't. + * + * When pages split, the key range is split across multiple pages. If not all + * of the old versions of the page are overwritten, or not all of the new pages + * are written, or some of the pages are corrupted, salvage will read different + * pages with overlapping key ranges, at different LSNs. + * + * We salvage all of the key ranges we find, at the latest LSN value: this means + * we may resurrect pages of deleted items, as page deletion doesn't write leaf + * pages and salvage will read and instantiate the contents of an old version of + * the deleted page. + * + * The leaf page array is sorted in key order, and secondarily on LSN: what this + * means is that for each new key range, the first page we find is the best page + * for that key. The process is to walk forward from each page until we reach + * a page with a starting key after the current page's stopping key. + * + * For each of page, check to see if they overlap the current page's key range. + * If they do, resolve the overlap. Because WiredTiger rarely splits pages, + * overlap resolution usually means discarding a page because the key ranges + * are the same, and one of the pages is simply an old version of the other. + * + * However, it's possible more complex resolution is necessary. For example, + * here's an improbably complex list of page ranges and LSNs: + * + * Page Range LSN + * 30 A-G 3 + * 31 C-D 4 + * 32 B-C 5 + * 33 C-F 6 + * 34 C-D 7 + * 35 F-M 8 + * 36 H-O 9 + * + * We walk forward from each page reviewing all other pages in the array that + * overlap the range. For each overlap, the current or the overlapping + * page is updated so the page with the most recent information for any range + * "owns" that range. Here's an example for page 30. + * + * Review page 31: because page 31 has the range C-D and a higher LSN than page + * 30, page 30 would "split" into two ranges, A-C and E-G, conceding the C-D + * range to page 31. The new track element would be inserted into array with + * the following result: + * + * Page Range LSN + * 30 A-C 3 << Changed WT_TRACK element + * 31 C-D 4 + * 32 B-C 5 + * 33 C-F 6 + * 34 C-D 7 + * 30 E-G 3 << New WT_TRACK element + * 35 F-M 8 + * 36 H-O 9 + * + * Continue the review of the first element, using its new values. + * + * Review page 32: because page 31 has the range B-C and a higher LSN than page + * 30, page 30's A-C range would be truncated, conceding the B-C range to page + * 32. + * 30 A-B 3 + * E-G 3 + * 31 C-D 4 + * 32 B-C 5 + * 33 C-F 6 + * 34 C-D 7 + * + * Review page 33: because page 33 has a starting key (C) past page 30's ending + * key (B), we stop evaluating page 30's A-B range, as there can be no further + * overlaps. + * + * This process is repeated for each page in the array. + * + * When page 33 is processed, we'd discover that page 33's C-F range overlaps + * page 30's E-G range, and page 30's E-G range would be updated, conceding the + * E-F range to page 33. + * + * This is not computationally expensive because we don't walk far forward in + * the leaf array because it's sorted by starting key, and because WiredTiger + * splits are rare, the chance of finding the kind of range overlap requiring + * re-sorting the array is small. + */ +static int +__slvg_col_range(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_TRACK *jtrk; + uint32_t i, j; + + /* + * DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR + * COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE + * BEING HANDLED. + * + * Walk the page array looking for overlapping key ranges, adjusting + * the ranges based on the LSN until there are no overlaps. + * + * DO NOT USE POINTERS INTO THE ARRAY: THE ARRAY IS RE-SORTED IN PLACE + * AS ENTRIES ARE SPLIT, SO ARRAY REFERENCES MUST ALWAYS BE ARRAY BASE + * PLUS OFFSET. + */ + for (i = 0; i < ss->pages_next; ++i) { + if (ss->pages[i] == NULL) + continue; + + /* Check for pages that overlap our page. */ + for (j = i + 1; j < ss->pages_next; ++j) { + if (ss->pages[j] == NULL) + continue; + /* + * We're done if this page starts after our stop, no + * subsequent pages can overlap our page. + */ + if (ss->pages[j]->col_start > + ss->pages[i]->col_stop) + break; + + /* There's an overlap, fix it up. */ + jtrk = ss->pages[j]; + WT_RET(__slvg_col_range_overlap(session, i, j, ss)); + + /* + * If the overlap resolution changed the entry's start + * key, the entry might have moved and the page array + * re-sorted, and pages[j] would reference a different + * page. We don't move forward if that happened, we + * re-process the slot again (by decrementing j before + * the loop's increment). + */ + if (ss->pages[j] != NULL && jtrk != ss->pages[j]) + --j; + } + } + return (0); +} + +/* + * __slvg_col_range_overlap -- + * Two column-store key ranges overlap, deal with it. + */ +static int +__slvg_col_range_overlap( + WT_SESSION_IMPL *session, uint32_t a_slot, uint32_t b_slot, WT_STUFF *ss) +{ + WT_TRACK *a_trk, *b_trk, *new; + uint32_t i; + + /* + * DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR + * COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE + * BEING HANDLED. + */ + a_trk = ss->pages[a_slot]; + b_trk = ss->pages[b_slot]; + + WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s and %s range overlap", + __wt_addr_string( + session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1), + __wt_addr_string( + session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2))); + + /* + * The key ranges of two WT_TRACK pages in the array overlap -- choose + * the ranges we're going to take from each. + * + * We can think of the overlap possibilities as 11 different cases: + * + * AAAAAAAAAAAAAAAAAA + * #1 BBBBBBBBBBBBBBBBBB pages are the same + * #2 BBBBBBBBBBBBB overlaps the beginning + * #3 BBBBBBBBBBBBBBBB overlaps the end + * #4 BBBBB B is a prefix of A + * #5 BBBBBB B is middle of A + * #6 BBBBBBBBBB B is a suffix of A + * + * and: + * + * BBBBBBBBBBBBBBBBBB + * #7 AAAAAAAAAAAAA same as #3 + * #8 AAAAAAAAAAAAAAAA same as #2 + * #9 AAAAA A is a prefix of B + * #10 AAAAAA A is middle of B + * #11 AAAAAAAAAA A is a suffix of B + * + * Note the leaf page array was sorted by key and a_trk appears earlier + * in the array than b_trk, so cases #2/8, #10 and #11 are impossible. + * + * Finally, there's one additional complicating factor -- final ranges + * are assigned based on the page's LSN. + */ + /* Case #2/8, #10, #11 */ + if (a_trk->col_start > b_trk->col_start) + WT_PANIC_RET( + session, EINVAL, "unexpected merge array sort order"); + + if (a_trk->col_start == b_trk->col_start) { /* Case #1, #4 and #9 */ + /* + * The secondary sort of the leaf page array was the page's LSN, + * in high-to-low order, which means a_trk has a higher LSN, and + * is more desirable, than b_trk. In cases #1 and #4 and #9, + * where the start of the range is the same for the two pages, + * this simplifies things, it guarantees a_trk has a higher LSN + * than b_trk. + */ + if (a_trk->col_stop >= b_trk->col_stop) + /* + * Case #1, #4: a_trk is a superset of b_trk, and a_trk + * is more desirable -- discard b_trk. + */ + goto delete_b; + + /* + * Case #9: b_trk is a superset of a_trk, but a_trk is more + * desirable: keep both but delete a_trk's key range from + * b_trk. + */ + b_trk->col_start = a_trk->col_stop + 1; + __slvg_col_trk_update_start(b_slot, ss); + F_SET(b_trk, WT_TRACK_MERGE); + goto merge; + } + + if (a_trk->col_stop == b_trk->col_stop) { /* Case #6 */ + if (a_trk->trk_gen > b_trk->trk_gen) + /* + * Case #6: a_trk is a superset of b_trk and a_trk is + * more desirable -- discard b_trk. + */ + goto delete_b; + + /* + * Case #6: a_trk is a superset of b_trk, but b_trk is more + * desirable: keep both but delete b_trk's key range from a_trk. + */ + a_trk->col_stop = b_trk->col_start - 1; + F_SET(a_trk, WT_TRACK_MERGE); + goto merge; + } + + if (a_trk->col_stop < b_trk->col_stop) { /* Case #3/7 */ + if (a_trk->trk_gen > b_trk->trk_gen) { + /* + * Case #3/7: a_trk is more desirable, delete a_trk's + * key range from b_trk; + */ + b_trk->col_start = a_trk->col_stop + 1; + __slvg_col_trk_update_start(b_slot, ss); + F_SET(b_trk, WT_TRACK_MERGE); + } else { + /* + * Case #3/7: b_trk is more desirable, delete b_trk's + * key range from a_trk; + */ + a_trk->col_stop = b_trk->col_start - 1; + F_SET(a_trk, WT_TRACK_MERGE); + } + goto merge; + } + + /* + * Case #5: a_trk is a superset of b_trk and a_trk is more desirable -- + * discard b_trk. + */ + if (a_trk->trk_gen > b_trk->trk_gen) { +delete_b: /* + * After page and overflow reconciliation, one (and only one) + * page can reference an overflow record. But, if we split a + * page into multiple chunks, any of the chunks might own any + * of the backing overflow records, so overflow records won't + * normally be discarded until after the merge phase completes. + * (The merge phase is where the final pages are written, and + * we figure out which overflow records are actually used.) + * If freeing a chunk and there are no other references to the + * underlying shared information, the overflow records must be + * useless, discard them to keep the final file size small. + */ + if (b_trk->shared->ref == 1) + for (i = 0; i < b_trk->trk_ovfl_cnt; ++i) + WT_RET(__slvg_trk_free(session, + &ss->ovfl[b_trk->trk_ovfl_slot[i]], 1)); + return (__slvg_trk_free(session, &ss->pages[b_slot], 1)); + } + + /* + * Case #5: b_trk is more desirable and is a middle chunk of a_trk. + * Split a_trk into two parts, the key range before b_trk and the + * key range after b_trk. + */ + WT_RET(__slvg_trk_split(session, a_trk, &new)); + + /* + * Second, reallocate the array of pages if necessary, and then insert + * the new element into the array after the existing element (that's + * probably wrong, but we'll fix it up in a second). + */ + WT_RET(__wt_realloc_def( + session, &ss->pages_allocated, ss->pages_next + 1, &ss->pages)); + memmove(ss->pages + a_slot + 1, ss->pages + a_slot, + (ss->pages_next - a_slot) * sizeof(*ss->pages)); + ss->pages[a_slot + 1] = new; + ++ss->pages_next; + + /* + * Third, set its start key to be the first key after the stop key of + * the middle chunk (that's b_trk), and its stop key to be the stop key + * of the original chunk, and call __slvg_col_trk_update_start. That + * function will re-sort the WT_TRACK array as necessary to move our + * new entry into the right sorted location. + */ + new->col_start = b_trk->col_stop + 1; + new->col_stop = a_trk->col_stop; + __slvg_col_trk_update_start(a_slot + 1, ss); + + /* + * Fourth, set the original WT_TRACK information to reference only + * the initial key space in the page, that is, everything up to the + * starting key of the middle chunk (that's b_trk). + */ + a_trk->col_stop = b_trk->col_start - 1; + + F_SET(new, WT_TRACK_MERGE); + F_SET(a_trk, WT_TRACK_MERGE); + +merge: WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s and %s require merge", + __wt_addr_string( + session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1), + __wt_addr_string( + session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2))); + return (0); +} + +/* + * __slvg_col_trk_update_start -- + * Update a column-store page's start key after an overlap. + */ +static void +__slvg_col_trk_update_start(uint32_t slot, WT_STUFF *ss) +{ + WT_TRACK *trk; + uint32_t i; + + trk = ss->pages[slot]; + + /* + * If we deleted an initial piece of the WT_TRACK name space, it may no + * longer be in the right location. + * + * For example, imagine page #1 has the key range 30-50, it split, and + * we wrote page #2 with key range 30-40, and page #3 key range with + * 40-50, where pages #2 and #3 have larger LSNs than page #1. When the + * key ranges were sorted, page #2 came first, then page #1 (because of + * their earlier start keys than page #3), and page #2 came before page + * #1 because of its LSN. When we resolve the overlap between page #2 + * and page #1, we truncate the initial key range of page #1, and it now + * sorts after page #3, because it has the same starting key of 40, and + * a lower LSN. + * + * We have already updated b_trk's start key; what we may have to do is + * re-sort some number of elements in the list. + */ + for (i = slot + 1; i < ss->pages_next; ++i) { + if (ss->pages[i] == NULL) + continue; + if (ss->pages[i]->col_start > trk->col_stop) + break; + } + i -= slot; + if (i > 1) + qsort(ss->pages + slot, (size_t)i, + sizeof(WT_TRACK *), __slvg_trk_compare_key); +} + +/* + * __slvg_col_range_missing -- + * Detect missing ranges from column-store files. + */ +static int +__slvg_col_range_missing(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_TRACK *trk; + uint64_t r; + uint32_t i; + + for (i = 0, r = 0; i < ss->pages_next; ++i) { + if ((trk = ss->pages[i]) == NULL) + continue; + if (trk->col_start != r + 1) { + WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s column-store missing range from %" + PRIu64 " to %" PRIu64 " inclusive", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, ss->tmp1), + r + 1, trk->col_start - 1)); + + /* + * We need to instantiate deleted items for the missing + * record range. + */ + trk->col_missing = r + 1; + F_SET(trk, WT_TRACK_MERGE); + } + r = trk->col_stop; + } + return (0); +} + +/* + * __slvg_modify_init -- + * Initialize a salvage page's modification information. + */ +static int +__slvg_modify_init(WT_SESSION_IMPL *session, WT_PAGE *page) +{ + WT_RET(__wt_page_modify_init(session, page)); + __wt_page_modify_set(session, page); + + return (0); +} + +/* + * __slvg_col_build_internal -- + * Build a column-store in-memory page that references all of the leaf + * pages we've found. + */ +static int +__slvg_col_build_internal( + WT_SESSION_IMPL *session, uint32_t leaf_cnt, WT_STUFF *ss) +{ + WT_ADDR *addr; + WT_DECL_RET; + WT_PAGE *page; + WT_PAGE_INDEX *pindex; + WT_REF *ref, **refp; + WT_TRACK *trk; + uint32_t i; + + addr = NULL; + + /* Allocate a column-store root (internal) page and fill it in. */ + WT_RET( + __wt_page_alloc(session, WT_PAGE_COL_INT, 1, leaf_cnt, 1, &page)); + WT_ERR(__slvg_modify_init(session, page)); + + pindex = WT_INTL_INDEX_COPY(page); + for (refp = pindex->index, i = 0; i < ss->pages_next; ++i) { + if ((trk = ss->pages[i]) == NULL) + continue; + + ref = *refp++; + ref->home = page; + ref->page = NULL; + + WT_ERR(__wt_calloc(session, 1, sizeof(WT_ADDR), &addr)); + WT_ERR(__wt_strndup( + session, trk->trk_addr, trk->trk_addr_size, &addr->addr)); + addr->size = trk->trk_addr_size; + addr->type = + trk->trk_ovfl_cnt == 0 ? WT_ADDR_LEAF_NO : WT_ADDR_LEAF; + ref->addr = addr; + addr = NULL; + + ref->key.recno = trk->col_start; + ref->state = WT_REF_DISK; + + /* + * If the page's key range is unmodified from when we read it + * (in other words, we didn't merge part of this page with + * another page), we can use the page without change, and the + * only thing we need to do is mark all overflow records the + * page references as in-use. + * + * If we did merge with another page, we have to build a page + * reflecting the updated key range. Note, that requires an + * additional pass to free the merge page's backing blocks. + */ + if (F_ISSET(trk, WT_TRACK_MERGE)) { + ss->merge_free = 1; + + WT_ERR(__slvg_col_build_leaf(session, trk, ref)); + } else + WT_ERR(__slvg_ovfl_ref_all(session, trk)); + ++ref; + } + + __wt_root_ref_init(&ss->root_ref, page, 1); + + if (0) { +err: if (addr != NULL) + __wt_free(session, addr); + __wt_page_out(session, &page); + } + return (ret); +} + +/* + * __slvg_col_build_leaf -- + * Build a column-store leaf page for a merged page. + */ +static int +__slvg_col_build_leaf(WT_SESSION_IMPL *session, WT_TRACK *trk, WT_REF *ref) +{ + WT_COL *save_col_var; + WT_DECL_RET; + WT_PAGE *page; + WT_SALVAGE_COOKIE *cookie, _cookie; + uint64_t skip, take; + uint32_t *entriesp, save_entries; + + cookie = &_cookie; + WT_CLEAR(*cookie); + + /* Get the original page, including the full in-memory setup. */ + WT_RET(__wt_page_in(session, ref, 0)); + page = ref->page; + + entriesp = page->type == WT_PAGE_COL_VAR ? + &page->pg_var_entries : &page->pg_fix_entries; + + save_col_var = page->pg_var_d; + save_entries = *entriesp; + + /* + * Calculate the number of K/V entries we are going to skip, and + * the total number of K/V entries we'll take from this page. + */ + cookie->skip = skip = trk->col_start - page->pg_var_recno; + cookie->take = take = (trk->col_stop - trk->col_start) + 1; + + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s merge discarding first %" PRIu64 " records, " + "then taking %" PRIu64 " records", + __wt_addr_string( + session, trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1), + skip, take)); + + /* Set the referenced flag on overflow pages we're using. */ + if (page->type == WT_PAGE_COL_VAR && trk->trk_ovfl_cnt != 0) + WT_ERR(__slvg_col_ovfl(session, trk, page, skip, take)); + + /* + * If we're missing some part of the range, the real start range is in + * trk->col_missing, else, it's in trk->col_start. Update the parent's + * reference as well as the page itself. + */ + if (trk->col_missing == 0) + page->pg_var_recno = trk->col_start; + else { + page->pg_var_recno = trk->col_missing; + cookie->missing = trk->col_start - trk->col_missing; + + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s merge inserting %" PRIu64 " missing records", + __wt_addr_string( + session, trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1), + cookie->missing)); + } + ref->key.recno = page->pg_var_recno; + + /* + * We can't discard the original blocks associated with this page now. + * (The problem is we don't want to overwrite any original information + * until the salvage run succeeds -- if we free the blocks now, the next + * merge page we write might allocate those blocks and overwrite them, + * and should the salvage run eventually fail, the original information + * would have been lost.) Clear the reference addr so eviction doesn't + * free the underlying blocks. + */ + __wt_free(session, ((WT_ADDR *)ref->addr)->addr); + __wt_free(session, ref->addr); + ref->addr = NULL; + + /* Write the new version of the leaf page to disk. */ + WT_ERR(__slvg_modify_init(session, page)); + WT_ERR(__wt_rec_write(session, ref, cookie, WT_SKIP_UPDATE_ERR)); + + /* Reset the page. */ + page->pg_var_d = save_col_var; + *entriesp = save_entries; + + ret = __wt_page_release(session, ref, 0); + if (ret == 0) + ret = __wt_rec_evict(session, ref, 1); + + if (0) { +err: WT_TRET(__wt_page_release(session, ref, 0)); + } + + return (ret); +} + +/* + * __slvg_col_ovfl_single -- + * Find a single overflow record in the merge page's list, and mark it as + * referenced. + */ +static int +__slvg_col_ovfl_single( + WT_SESSION_IMPL *session, WT_TRACK *trk, WT_CELL_UNPACK *unpack) +{ + WT_TRACK *ovfl; + uint32_t i; + + /* + * Search the list of overflow records for this page -- we should find + * exactly one match, and we mark it as referenced. + */ + for (i = 0; i < trk->trk_ovfl_cnt; ++i) { + ovfl = trk->ss->ovfl[trk->trk_ovfl_slot[i]]; + if (unpack->size == ovfl->trk_addr_size && + memcmp(unpack->data, ovfl->trk_addr, unpack->size) == 0) + return (__slvg_ovfl_ref(session, ovfl, 0)); + } + + WT_PANIC_RET(session, + EINVAL, "overflow record at column-store page merge not found"); +} + +/* + * __slvg_col_ovfl -- + * Mark overflow items referenced by the merged page. + */ +static int +__slvg_col_ovfl(WT_SESSION_IMPL *session, + WT_TRACK *trk, WT_PAGE *page, uint64_t skip, uint64_t take) +{ + WT_CELL_UNPACK unpack; + WT_CELL *cell; + WT_COL *cip; + WT_DECL_RET; + uint64_t recno, start, stop; + uint32_t i; + + /* + * Merging a variable-length column-store page, and we took some number + * of records, figure out which (if any) overflow records we used. + */ + recno = page->pg_var_recno; + start = recno + skip; + stop = (recno + skip + take) - 1; + + WT_COL_FOREACH(page, cip, i) { + cell = WT_COL_PTR(page, cip); + __wt_cell_unpack(cell, &unpack); + recno += __wt_cell_rle(&unpack); + + /* + * I keep getting this calculation wrong, so here's the logic. + * Start is the first record we want, stop is the last record + * we want. The record number has already been incremented one + * past the maximum record number for this page entry, that is, + * it's set to the first record number for the next page entry. + * The test of start should be greater-than (not greater-than- + * or-equal), because of that increment, if the record number + * equals start, we want the next record, not this one. The + * test against stop is greater-than, not greater-than-or-equal + * because stop is the last record wanted, if the record number + * equals stop, we want the next record. + */ + if (recno > start && unpack.type == WT_CELL_VALUE_OVFL) { + ret = __slvg_col_ovfl_single(session, trk, &unpack); + + /* + * When handling overlapping ranges on variable-length + * column-store leaf pages, we split ranges without + * considering if we were splitting RLE units. (See + * note at the beginning of this file for explanation + * of the overall process.) If the RLE unit was on-page, + * we can simply write it again. If the RLE unit was an + * overflow value that's already been used by another + * row (from some other page created by a range split), + * there's not much to do, this row can't reference an + * overflow record we don't have: delete the row. + */ + if (ret == EBUSY) { + __wt_cell_type_reset(session, + cell, WT_CELL_VALUE_OVFL, WT_CELL_DEL); + ret = 0; + } + WT_RET(ret); + } + if (recno > stop) + break; + } + return (0); +} + +/* + * __slvg_row_range -- + * Figure out the leaf pages we need and discard everything else. At the + * same time, tag the overflow pages they reference. + */ +static int +__slvg_row_range(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_TRACK *jtrk; + WT_BTREE *btree; + uint32_t i, j; + int cmp; + + btree = S2BT(session); + + /* + * DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR + * COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE + * BEING HANDLED. + * + * Walk the page array looking for overlapping key ranges, adjusting + * the ranges based on the LSN until there are no overlaps. + * + * DO NOT USE POINTERS INTO THE ARRAY: THE ARRAY IS RE-SORTED IN PLACE + * AS ENTRIES ARE SPLIT, SO ARRAY REFERENCES MUST ALWAYS BE ARRAY BASE + * PLUS OFFSET. + */ + for (i = 0; i < ss->pages_next; ++i) { + if (ss->pages[i] == NULL) + continue; + + /* Check for pages that overlap our page. */ + for (j = i + 1; j < ss->pages_next; ++j) { + if (ss->pages[j] == NULL) + continue; + /* + * We're done if this page starts after our stop, no + * subsequent pages can overlap our page. + */ + WT_RET(__wt_compare(session, btree->collator, + &ss->pages[j]->row_start, &ss->pages[i]->row_stop, + &cmp)); + if (cmp > 0) + break; + + /* There's an overlap, fix it up. */ + jtrk = ss->pages[j]; + WT_RET(__slvg_row_range_overlap(session, i, j, ss)); + + /* + * If the overlap resolution changed the entry's start + * key, the entry might have moved and the page array + * re-sorted, and pages[j] would reference a different + * page. We don't move forward if that happened, we + * re-process the slot again (by decrementing j before + * the loop's increment). + */ + if (ss->pages[j] != NULL && jtrk != ss->pages[j]) + --j; + } + } + return (0); +} + +/* + * __slvg_row_range_overlap -- + * Two row-store key ranges overlap, deal with it. + */ +static int +__slvg_row_range_overlap( + WT_SESSION_IMPL *session, uint32_t a_slot, uint32_t b_slot, WT_STUFF *ss) +{ + WT_BTREE *btree; + WT_TRACK *a_trk, *b_trk, *new; + uint32_t i; + int start_cmp, stop_cmp; + + /* + * DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR + * COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE + * BEING HANDLED. + */ + btree = S2BT(session); + + a_trk = ss->pages[a_slot]; + b_trk = ss->pages[b_slot]; + + WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s and %s range overlap", + __wt_addr_string( + session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1), + __wt_addr_string( + session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2))); + + /* + * The key ranges of two WT_TRACK pages in the array overlap -- choose + * the ranges we're going to take from each. + * + * We can think of the overlap possibilities as 11 different cases: + * + * AAAAAAAAAAAAAAAAAA + * #1 BBBBBBBBBBBBBBBBBB pages are the same + * #2 BBBBBBBBBBBBB overlaps the beginning + * #3 BBBBBBBBBBBBBBBB overlaps the end + * #4 BBBBB B is a prefix of A + * #5 BBBBBB B is middle of A + * #6 BBBBBBBBBB B is a suffix of A + * + * and: + * + * BBBBBBBBBBBBBBBBBB + * #7 AAAAAAAAAAAAA same as #3 + * #8 AAAAAAAAAAAAAAAA same as #2 + * #9 AAAAA A is a prefix of B + * #10 AAAAAA A is middle of B + * #11 AAAAAAAAAA A is a suffix of B + * + * Note the leaf page array was sorted by key and a_trk appears earlier + * in the array than b_trk, so cases #2/8, #10 and #11 are impossible. + * + * Finally, there's one additional complicating factor -- final ranges + * are assigned based on the page's LSN. + */ +#define A_TRK_START (&a_trk->row_start) +#define A_TRK_STOP (&a_trk->row_stop) +#define B_TRK_START (&b_trk->row_start) +#define B_TRK_STOP (&b_trk->row_stop) +#define SLOT_START(i) (&ss->pages[i]->row_start) +#define __slvg_key_copy(session, dst, src) \ + __wt_buf_set(session, dst, (src)->data, (src)->size) + + WT_RET(__wt_compare( + session, btree->collator, A_TRK_START, B_TRK_START, &start_cmp)); + WT_RET(__wt_compare( + session, btree->collator, A_TRK_STOP, B_TRK_STOP, &stop_cmp)); + + if (start_cmp > 0) /* Case #2/8, #10, #11 */ + WT_PANIC_RET( + session, EINVAL, "unexpected merge array sort order"); + + if (start_cmp == 0) { /* Case #1, #4, #9 */ + /* + * The secondary sort of the leaf page array was the page's LSN, + * in high-to-low order, which means a_trk has a higher LSN, and + * is more desirable, than b_trk. In cases #1 and #4 and #9, + * where the start of the range is the same for the two pages, + * this simplifies things, it guarantees a_trk has a higher LSN + * than b_trk. + */ + if (stop_cmp >= 0) + /* + * Case #1, #4: a_trk is a superset of b_trk, and a_trk + * is more desirable -- discard b_trk. + */ + goto delete_b; + + /* + * Case #9: b_trk is a superset of a_trk, but a_trk is more + * desirable: keep both but delete a_trk's key range from + * b_trk. + */ + WT_RET(__slvg_row_trk_update_start( + session, A_TRK_STOP, b_slot, ss)); + F_SET(b_trk, WT_TRACK_CHECK_START | WT_TRACK_MERGE); + goto merge; + } + + if (stop_cmp == 0) { /* Case #6 */ + if (a_trk->trk_gen > b_trk->trk_gen) + /* + * Case #6: a_trk is a superset of b_trk and a_trk is + * more desirable -- discard b_trk. + */ + goto delete_b; + + /* + * Case #6: a_trk is a superset of b_trk, but b_trk is more + * desirable: keep both but delete b_trk's key range from a_trk. + */ + WT_RET(__slvg_key_copy(session, A_TRK_STOP, B_TRK_START)); + F_SET(a_trk, WT_TRACK_CHECK_STOP | WT_TRACK_MERGE); + goto merge; + } + + if (stop_cmp < 0) { /* Case #3/7 */ + if (a_trk->trk_gen > b_trk->trk_gen) { + /* + * Case #3/7: a_trk is more desirable, delete a_trk's + * key range from b_trk; + */ + WT_RET(__slvg_row_trk_update_start( + session, A_TRK_STOP, b_slot, ss)); + F_SET(b_trk, WT_TRACK_CHECK_START | WT_TRACK_MERGE); + } else { + /* + * Case #3/7: b_trk is more desirable, delete b_trk's + * key range from a_trk; + */ + WT_RET(__slvg_key_copy( + session, A_TRK_STOP, B_TRK_START)); + F_SET(a_trk, WT_TRACK_CHECK_STOP | WT_TRACK_MERGE); + } + goto merge; + } + + /* + * Case #5: a_trk is a superset of b_trk and a_trk is more desirable -- + * discard b_trk. + */ + if (a_trk->trk_gen > b_trk->trk_gen) { +delete_b: /* + * After page and overflow reconciliation, one (and only one) + * page can reference an overflow record. But, if we split a + * page into multiple chunks, any of the chunks might own any + * of the backing overflow records, so overflow records won't + * normally be discarded until after the merge phase completes. + * (The merge phase is where the final pages are written, and + * we figure out which overflow records are actually used.) + * If freeing a chunk and there are no other references to the + * underlying shared information, the overflow records must be + * useless, discard them to keep the final file size small. + */ + if (b_trk->shared->ref == 1) + for (i = 0; i < b_trk->trk_ovfl_cnt; ++i) + WT_RET(__slvg_trk_free(session, + &ss->ovfl[b_trk->trk_ovfl_slot[i]], 1)); + return (__slvg_trk_free(session, &ss->pages[b_slot], 1)); + } + + /* + * Case #5: b_trk is more desirable and is a middle chunk of a_trk. + * Split a_trk into two parts, the key range before b_trk and the + * key range after b_trk. + */ + WT_RET(__slvg_trk_split(session, a_trk, &new)); + + /* + * Second, reallocate the array of pages if necessary, and then insert + * the new element into the array after the existing element (that's + * probably wrong, but we'll fix it up in a second). + */ + WT_RET(__wt_realloc_def( + session, &ss->pages_allocated, ss->pages_next + 1, &ss->pages)); + memmove(ss->pages + a_slot + 1, ss->pages + a_slot, + (ss->pages_next - a_slot) * sizeof(*ss->pages)); + ss->pages[a_slot + 1] = new; + ++ss->pages_next; + + /* + * Third, set its its stop key to be the stop key of the original chunk, + * and call __slvg_row_trk_update_start. That function will both set + * the start key to be the first key after the stop key of the middle + * chunk (that's b_trk), and re-sort the WT_TRACK array as necessary to + * move our new entry into the right sorted location. + */ + WT_RET(__slvg_key_copy(session, &new->row_stop, A_TRK_STOP)); + WT_RET( + __slvg_row_trk_update_start(session, B_TRK_STOP, a_slot + 1, ss)); + + /* + * Fourth, set the original WT_TRACK information to reference only + * the initial key space in the page, that is, everything up to the + * starting key of the middle chunk (that's b_trk). + */ + WT_RET(__slvg_key_copy(session, A_TRK_STOP, B_TRK_START)); + F_SET(new, WT_TRACK_CHECK_START); + F_SET(a_trk, WT_TRACK_CHECK_STOP); + + F_SET(new, WT_TRACK_MERGE); + F_SET(a_trk, WT_TRACK_MERGE); + +merge: WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s and %s require merge", + __wt_addr_string( + session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1), + __wt_addr_string( + session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2))); + return (0); +} + +/* + * __slvg_row_trk_update_start -- + * Update a row-store page's start key after an overlap. + */ +static int +__slvg_row_trk_update_start( + WT_SESSION_IMPL *session, WT_ITEM *stop, uint32_t slot, WT_STUFF *ss) +{ + WT_BTREE *btree; + WT_DECL_ITEM(dsk); + WT_DECL_ITEM(key); + WT_DECL_RET; + WT_PAGE *page; + WT_ROW *rip; + WT_TRACK *trk; + uint32_t i; + int cmp, found; + + btree = S2BT(session); + page = NULL; + found = 0; + + trk = ss->pages[slot]; + + /* + * If we deleted an initial piece of the WT_TRACK name space, it may no + * longer be in the right location. + * + * For example, imagine page #1 has the key range 30-50, it split, and + * we wrote page #2 with key range 30-40, and page #3 key range with + * 40-50, where pages #2 and #3 have larger LSNs than page #1. When the + * key ranges were sorted, page #2 came first, then page #1 (because of + * their earlier start keys than page #3), and page #2 came before page + * #1 because of its LSN. When we resolve the overlap between page #2 + * and page #1, we truncate the initial key range of page #1, and it now + * sorts after page #3, because it has the same starting key of 40, and + * a lower LSN. + * + * First, update the WT_TRACK start key based on the specified stop key. + * + * Read and instantiate the WT_TRACK page (we don't have to verify the + * page, nor do we have to be quiet on error, we've already read this + * page successfully). + */ + WT_RET(__wt_scr_alloc(session, trk->trk_size, &dsk)); + WT_ERR(__wt_bt_read(session, dsk, trk->trk_addr, trk->trk_addr_size)); + WT_ERR(__wt_page_inmem(session, NULL, dsk->mem, 0, &page)); + + /* + * Walk the page, looking for a key sorting greater than the specified + * stop key -- that's our new start key. + */ + WT_ERR(__wt_scr_alloc(session, 0, &key)); + WT_ROW_FOREACH(page, rip, i) { + WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0)); + WT_ERR(__wt_compare(session, btree->collator, key, stop, &cmp)); + if (cmp > 0) { + found = 1; + break; + } + } + + /* + * We know that at least one key on the page sorts after the specified + * stop key, otherwise the page would have entirely overlapped and we + * would have discarded it, we wouldn't be here. Therefore, this test + * is safe. (But, it never hurts to check.) + */ + WT_ERR_TEST(!found, WT_ERROR); + WT_ERR(__slvg_key_copy(session, &trk->row_start, key)); + + /* + * We may need to re-sort some number of elements in the list. Walk + * forward in the list until reaching an entry which cannot overlap + * the adjusted entry. If it's more than a single slot, re-sort the + * entries. + */ + for (i = slot + 1; i < ss->pages_next; ++i) { + if (ss->pages[i] == NULL) + continue; + WT_ERR(__wt_compare(session, + btree->collator, SLOT_START(i), &trk->row_stop, &cmp)); + if (cmp > 0) + break; + } + i -= slot; + if (i > 1) + qsort(ss->pages + slot, (size_t)i, + sizeof(WT_TRACK *), __slvg_trk_compare_key); + +err: if (page != NULL) + __wt_page_out(session, &page); + __wt_scr_free(&dsk); + __wt_scr_free(&key); + + return (ret); +} + +/* + * __slvg_row_build_internal -- + * Build a row-store in-memory page that references all of the leaf + * pages we've found. + */ +static int +__slvg_row_build_internal( + WT_SESSION_IMPL *session, uint32_t leaf_cnt, WT_STUFF *ss) +{ + WT_ADDR *addr; + WT_DECL_RET; + WT_PAGE *page; + WT_PAGE_INDEX *pindex; + WT_REF *ref, **refp; + WT_TRACK *trk; + uint32_t i; + + addr = NULL; + + /* Allocate a row-store root (internal) page and fill it in. */ + WT_RET( + __wt_page_alloc(session, WT_PAGE_ROW_INT, 0, leaf_cnt, 1, &page)); + WT_ERR(__slvg_modify_init(session, page)); + + pindex = WT_INTL_INDEX_COPY(page); + for (refp = pindex->index, i = 0; i < ss->pages_next; ++i) { + if ((trk = ss->pages[i]) == NULL) + continue; + + ref = *refp++; + ref->home = page; + ref->page = NULL; + + WT_ERR(__wt_calloc(session, 1, sizeof(WT_ADDR), &addr)); + WT_ERR(__wt_strndup( + session, trk->trk_addr, trk->trk_addr_size, &addr->addr)); + addr->size = trk->trk_addr_size; + addr->type = + trk->trk_ovfl_cnt == 0 ? WT_ADDR_LEAF_NO : WT_ADDR_LEAF; + ref->addr = addr; + addr = NULL; + + __wt_ref_key_clear(ref); + ref->state = WT_REF_DISK; + + /* + * If the page's key range is unmodified from when we read it + * (in other words, we didn't merge part of this page with + * another page), we can use the page without change, and the + * only thing we need to do is mark all overflow records the + * page references as in-use. + * + * If we did merge with another page, we have to build a page + * reflecting the updated key range. Note, that requires an + * additional pass to free the merge page's backing blocks. + */ + if (F_ISSET(trk, WT_TRACK_MERGE)) { + ss->merge_free = 1; + + WT_ERR(__slvg_row_build_leaf(session, trk, ref, ss)); + } else { + WT_ERR(__wt_row_ikey_incr(session, page, 0, + trk->row_start.data, trk->row_start.size, + &ref->key.ikey)); + + WT_ERR(__slvg_ovfl_ref_all(session, trk)); + } + ++ref; + } + + __wt_root_ref_init(&ss->root_ref, page, 0); + + if (0) { +err: if (addr != NULL) + __wt_free(session, addr); + __wt_page_out(session, &page); + } + return (ret); +} + +/* + * __slvg_row_build_leaf -- + * Build a row-store leaf page for a merged page. + */ +static int +__slvg_row_build_leaf( + WT_SESSION_IMPL *session, WT_TRACK *trk, WT_REF *ref, WT_STUFF *ss) +{ + WT_BTREE *btree; + WT_DECL_ITEM(key); + WT_DECL_RET; + WT_PAGE *page; + WT_ROW *rip; + WT_SALVAGE_COOKIE *cookie, _cookie; + uint32_t i, skip_start, skip_stop; + int cmp; + + btree = S2BT(session); + page = NULL; + + cookie = &_cookie; + WT_CLEAR(*cookie); + + /* Allocate temporary space in which to instantiate the keys. */ + WT_RET(__wt_scr_alloc(session, 0, &key)); + + /* Get the original page, including the full in-memory setup. */ + WT_ERR(__wt_page_in(session, ref, 0)); + page = ref->page; + + /* + * Figure out how many page keys we want to take and how many we want + * to skip. + * + * If checking the starting range key, the key we're searching for will + * be equal to the starting range key. This is because we figured out + * the true merged-page start key as part of discarding initial keys + * from the page (see the __slvg_row_range_overlap function, and its + * calls to __slvg_row_trk_update_start for more information). + * + * If checking the stopping range key, we want the keys on the page that + * are less-than the stopping range key. This is because we copied a + * key from another page to define this page's stop range: that page is + * the page that owns the "equal to" range space. + */ + skip_start = skip_stop = 0; + if (F_ISSET(trk, WT_TRACK_CHECK_START)) + WT_ROW_FOREACH(page, rip, i) { + WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0)); + + /* + * >= is correct: see the comment above. + */ + WT_ERR(__wt_compare(session, + btree->collator, key, &trk->row_start, &cmp)); + if (cmp >= 0) + break; + if (WT_VERBOSE_ISSET(session, WT_VERB_SALVAGE)) { + WT_ERR(__wt_buf_set_printable(session, + ss->tmp1, key->data, key->size)); + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s merge discarding leading key %.*s", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, + ss->tmp2), (int)ss->tmp1->size, + (char *)ss->tmp1->data)); + } + ++skip_start; + } + if (F_ISSET(trk, WT_TRACK_CHECK_STOP)) + WT_ROW_FOREACH_REVERSE(page, rip, i) { + WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0)); + + /* + * < is correct: see the comment above. + */ + WT_ERR(__wt_compare(session, + btree->collator, key, &trk->row_stop, &cmp)); + if (cmp < 0) + break; + if (WT_VERBOSE_ISSET(session, WT_VERB_SALVAGE)) { + WT_ERR(__wt_buf_set_printable(session, + ss->tmp1, key->data, key->size)); + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s merge discarding trailing key %.*s", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, + ss->tmp2), (int)ss->tmp1->size, + (char *)ss->tmp1->data)); + } + ++skip_stop; + } + + /* We should have selected some entries, but not the entire page. */ + WT_ASSERT(session, + skip_start + skip_stop > 0 && + skip_start + skip_stop < page->pg_row_entries); + + /* + * Take a copy of this page's first key to define the start of + * its range. The key may require processing, otherwise, it's + * a copy from the page. + */ + rip = page->pg_row_d + skip_start; + WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0)); + WT_ERR(__wt_row_ikey_incr(session, + ref->home, 0, key->data, key->size, &ref->key.ikey)); + + /* Set the referenced flag on overflow pages we're using. */ + if (trk->trk_ovfl_cnt != 0) + WT_ERR(__slvg_row_ovfl(session, + trk, page, skip_start, page->pg_row_entries - skip_stop)); + + /* + * Change the page to reflect the correct record count: there is no + * need to copy anything on the page itself, the entries value limits + * the number of page items. + */ + page->pg_row_entries -= skip_stop; + cookie->skip = skip_start; + + /* + * We can't discard the original blocks associated with this page now. + * (The problem is we don't want to overwrite any original information + * until the salvage run succeeds -- if we free the blocks now, the next + * merge page we write might allocate those blocks and overwrite them, + * and should the salvage run eventually fail, the original information + * would have been lost.) Clear the reference addr so eviction doesn't + * free the underlying blocks. + */ + __wt_free(session, ((WT_ADDR *)ref->addr)->addr); + __wt_free(session, ref->addr); + ref->addr = NULL; + + /* Write the new version of the leaf page to disk. */ + WT_ERR(__slvg_modify_init(session, page)); + WT_ERR(__wt_rec_write(session, ref, cookie, WT_SKIP_UPDATE_ERR)); + + /* Reset the page. */ + page->pg_row_entries += skip_stop; + + /* + * Discard our hazard pointer and evict the page, updating the + * parent's reference. + */ + ret = __wt_page_release(session, ref, 0); + if (ret == 0) + ret = __wt_rec_evict(session, ref, 1); + + if (0) { +err: WT_TRET(__wt_page_release(session, ref, 0)); + } + __wt_scr_free(&key); + + return (ret); +} + +/* + * __slvg_row_ovfl_single -- + * Find a single overflow record in the merge page's list, and mark it as + * referenced. + */ +static int +__slvg_row_ovfl_single(WT_SESSION_IMPL *session, WT_TRACK *trk, WT_CELL *cell) +{ + WT_CELL_UNPACK unpack; + WT_TRACK *ovfl; + uint32_t i; + + /* Unpack the cell, and check if it's an overflow record. */ + __wt_cell_unpack(cell, &unpack); + if (unpack.type != WT_CELL_KEY_OVFL && + unpack.type != WT_CELL_VALUE_OVFL) + return (0); + + /* + * Search the list of overflow records for this page -- we should find + * exactly one match, and we mark it as referenced. + */ + for (i = 0; i < trk->trk_ovfl_cnt; ++i) { + ovfl = trk->ss->ovfl[trk->trk_ovfl_slot[i]]; + if (unpack.size == ovfl->trk_addr_size && + memcmp(unpack.data, ovfl->trk_addr, unpack.size) == 0) + return (__slvg_ovfl_ref(session, ovfl, 1)); + } + + WT_PANIC_RET(session, + EINVAL, "overflow record at row-store page merge not found"); +} + +/* + * __slvg_row_ovfl -- + * Mark overflow items referenced by the merged page. + */ +static int +__slvg_row_ovfl(WT_SESSION_IMPL *session, + WT_TRACK *trk, WT_PAGE *page, uint32_t start, uint32_t stop) +{ + WT_CELL *cell; + WT_ROW *rip; + void *copy; + + /* + * We're merging a row-store page, and we took some number of records, + * figure out which (if any) overflow records we used. + */ + for (rip = page->pg_row_d + start; start < stop; ++start, ++rip) { + copy = WT_ROW_KEY_COPY(rip); + (void)__wt_row_leaf_key_info( + page, copy, NULL, &cell, NULL, NULL); + if (cell != NULL) + WT_RET(__slvg_row_ovfl_single(session, trk, cell)); + cell = __wt_row_leaf_value_cell(page, rip, NULL); + if (cell != NULL) + WT_RET(__slvg_row_ovfl_single(session, trk, cell)); + } + return (0); +} + +/* + * __slvg_trk_compare_addr -- + * Compare two WT_TRACK array entries by address cookie. + */ +static int +__slvg_trk_compare_addr(const void *a, const void *b) +{ + WT_DECL_RET; + WT_TRACK *a_trk, *b_trk; + size_t len; + + a_trk = *(WT_TRACK **)a; + b_trk = *(WT_TRACK **)b; + + /* + * We don't care about the order because these are opaque cookies -- + * we're just sorting them so we can binary search instead of linear + * search. + */ + len = WT_MIN(a_trk->trk_addr_size, b_trk->trk_addr_size); + ret = memcmp(a_trk->trk_addr, b_trk->trk_addr, len); + if (ret == 0) + ret = a_trk->trk_addr_size > b_trk->trk_addr_size ? -1 : 1; + return (ret); +} + +/* + * __slvg_ovfl_compare -- + * Bsearch comparison routine for the overflow array. + */ +static int +__slvg_ovfl_compare(const void *a, const void *b) +{ + WT_ADDR *addr; + WT_DECL_RET; + WT_TRACK *trk; + size_t len; + + addr = (WT_ADDR *)a; + trk = *(WT_TRACK **)b; + + len = WT_MIN(trk->trk_addr_size, addr->size); + ret = memcmp(addr->addr, trk->trk_addr, len); + if (ret == 0 && addr->size != trk->trk_addr_size) + ret = addr->size < trk->trk_addr_size ? -1 : 1; + return (ret); +} + +/* + * __slvg_ovfl_reconcile -- + * Review relationships between leaf pages and the overflow pages, delete + * leaf pages until there's a one-to-one relationship between leaf and overflow + * pages. + */ +static int +__slvg_ovfl_reconcile(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_ADDR *addr; + WT_DECL_RET; + WT_TRACK **searchp, *trk; + uint32_t i, j, *slot; + + slot = NULL; + + /* + * If an overflow page is referenced more than once, discard leaf pages + * with the lowest LSNs until overflow pages are only referenced once. + * + * This requires sorting the page list by LSN, and the overflow array + * by address cookie. + */ + qsort(ss->pages, + (size_t)ss->pages_next, sizeof(WT_TRACK *), __slvg_trk_compare_gen); + qsort(ss->ovfl, + (size_t)ss->ovfl_next, sizeof(WT_TRACK *), __slvg_trk_compare_addr); + + /* + * Walk the list of pages and discard any pages referencing non-existent + * overflow pages or referencing overflow pages also referenced by pages + * with higher LSNs. Our caller sorted the page list by LSN, high to + * low, so we don't have to do explicit testing of the page LSNs, the + * first page to reference an overflow page is the best page to own it. + */ + for (i = 0; i < ss->pages_next; ++i) { + if ((trk = ss->pages[i]) == NULL || trk->trk_ovfl_cnt == 0) + continue; + + WT_ERR(__wt_calloc_def(session, trk->trk_ovfl_cnt, &slot)); + for (j = 0; j < trk->trk_ovfl_cnt; ++j) { + addr = &trk->trk_ovfl_addr[j]; + searchp = bsearch(addr, ss->ovfl, ss->ovfl_next, + sizeof(WT_TRACK *), __slvg_ovfl_compare); + + /* + * If the overflow page doesn't exist or if another page + * has already claimed it, this leaf page isn't usable. + */ + if (searchp != NULL && + !F_ISSET(*searchp, WT_TRACK_OVFL_REFD)) { + /* + * Convert each block address into a slot in the + * list of overflow pages as we go. + */ + slot[j] = (uint32_t)(searchp - ss->ovfl); + F_SET(*searchp, WT_TRACK_OVFL_REFD); + continue; + } + + WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE, + "%s references unavailable overflow page %s", + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, ss->tmp1), + __wt_addr_string(session, + addr->addr, addr->size, ss->tmp2))); + + /* + * Clear the "referenced" flag for any overflow pages + * already claimed by this leaf page some other page + * might claim them. + */ + while (j > 0) + F_CLR(ss->ovfl[slot[--j]], WT_TRACK_OVFL_REFD); + trk = NULL; + WT_ERR(__slvg_trk_free(session, &ss->pages[i], 1)); + break; + } + + /* + * We now have a reference to the overflow WT_TRACK, and so no + * longer need the page's address array, discard it. Note, we + * potentially freed the WT_TRACK in the loop above, check it's + * still valid. + */ + if (trk == NULL) + __wt_free(session, slot); + else { + __slvg_trk_free_addr(session, trk); + + trk->trk_ovfl_slot = slot; + slot = NULL; + } + } + return (0); + +err: __wt_free(session, slot); + return (ret); +} + +/* + * __slvg_trk_compare_key -- + * Compare two WT_TRACK array entries by key, and secondarily, by LSN. + */ +static int +__slvg_trk_compare_key(const void *a, const void *b) +{ + WT_SESSION_IMPL *session; + WT_TRACK *a_trk, *b_trk; + uint64_t a_gen, a_recno, b_gen, b_recno; + int cmp; + + a_trk = *(WT_TRACK **)a; + b_trk = *(WT_TRACK **)b; + + if (a_trk == NULL) + return (b_trk == NULL ? 0 : 1); + if (b_trk == NULL) + return (-1); + + switch (a_trk->ss->page_type) { + case WT_PAGE_COL_FIX: + case WT_PAGE_COL_VAR: + a_recno = a_trk->col_start; + b_recno = b_trk->col_start; + if (a_recno == b_recno) + break; + if (a_recno > b_recno) + return (1); + if (a_recno < b_recno) + return (-1); + break; + case WT_PAGE_ROW_LEAF: + /* + * XXX + * __wt_compare can potentially fail, and we're ignoring that + * error because this routine is called as an underlying qsort + * routine. + */ + session = a_trk->ss->session; + (void)__wt_compare(session, S2BT(session)->collator, + &a_trk->row_start, &b_trk->row_start, &cmp); + if (cmp != 0) + return (cmp); + break; + } + + /* + * If the primary keys compare equally, differentiate based on LSN. + * Sort from highest LSN to lowest, that is, the earlier pages in + * the array are more desirable. + */ + a_gen = a_trk->trk_gen; + b_gen = b_trk->trk_gen; + return (a_gen > b_gen ? -1 : (a_gen < b_gen ? 1 : 0)); +} + +/* + * __slvg_trk_compare_gen -- + * Compare two WT_TRACK array entries by LSN. + */ +static int +__slvg_trk_compare_gen(const void *a, const void *b) +{ + WT_TRACK *a_trk, *b_trk; + uint64_t a_gen, b_gen; + + a_trk = *(WT_TRACK **)a; + b_trk = *(WT_TRACK **)b; + + /* + * Sort from highest LSN to lowest, that is, the earlier pages in the + * array are more desirable. + */ + a_gen = a_trk->trk_gen; + b_gen = b_trk->trk_gen; + return (a_gen > b_gen ? -1 : (a_gen < b_gen ? 1 : 0)); +} + +/* + * __slvg_merge_block_free -- + * Clean up backing file and overflow blocks after the merge phase. + */ +static int +__slvg_merge_block_free(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_TRACK *trk; + uint32_t i; + + /* Free any underlying file blocks for merged pages. */ + for (i = 0; i < ss->pages_next; ++i) { + if ((trk = ss->pages[i]) == NULL) + continue; + if (F_ISSET(trk, WT_TRACK_MERGE)) + WT_RET(__slvg_trk_free(session, &ss->pages[i], 1)); + } + + /* Free any unused overflow records. */ + return (__slvg_ovfl_discard(session, ss)); +} + +/* + * __slvg_ovfl_ref -- + * Reference an overflow page, checking for multiple references. + */ +static int +__slvg_ovfl_ref(WT_SESSION_IMPL *session, WT_TRACK *trk, int multi_panic) +{ + if (F_ISSET(trk, WT_TRACK_OVFL_REFD)) { + if (!multi_panic) + return (EBUSY); + WT_PANIC_RET(session, EINVAL, + "overflow record unexpectedly referenced multiple times " + "during leaf page merge"); + } + + F_SET(trk, WT_TRACK_OVFL_REFD); + return (0); +} + +/* + * __slvg_ovfl_ref_all -- + * Reference all of the page's overflow pages. + */ +static int +__slvg_ovfl_ref_all(WT_SESSION_IMPL *session, WT_TRACK *trk) +{ + uint32_t i; + + for (i = 0; i < trk->trk_ovfl_cnt; ++i) + WT_RET(__slvg_ovfl_ref( + session, trk->ss->ovfl[trk->trk_ovfl_slot[i]], 1)); + + return (0); +} + +/* + * __slvg_ovfl_discard -- + * Discard unused overflow pages. + */ +static int +__slvg_ovfl_discard(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + WT_TRACK *trk; + uint32_t i; + + /* + * Walk the overflow page array: if an overflow page isn't referenced, + * add its file blocks to the free list. + * + * Clear the reference flag (it's reused to figure out if the overflow + * record is referenced, but never used, by merged pages). + */ + for (i = 0; i < ss->ovfl_next; ++i) { + if ((trk = ss->ovfl[i]) == NULL) + continue; + + if (F_ISSET(trk, WT_TRACK_OVFL_REFD)) { + F_CLR(trk, WT_TRACK_OVFL_REFD); + continue; + } + WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s unused overflow page", + __wt_addr_string( + session, trk->trk_addr, trk->trk_addr_size, ss->tmp1))); + WT_RET(__slvg_trk_free(session, &ss->ovfl[i], 1)); + } + + return (0); +} + +/* + * __slvg_cleanup -- + * Discard memory allocated to the page and overflow arrays. + */ +static int +__slvg_cleanup(WT_SESSION_IMPL *session, WT_STUFF *ss) +{ + uint32_t i; + + /* Discard the leaf page array. */ + for (i = 0; i < ss->pages_next; ++i) + if (ss->pages[i] != NULL) + WT_RET(__slvg_trk_free(session, &ss->pages[i], 0)); + __wt_free(session, ss->pages); + + /* Discard the ovfl page array. */ + for (i = 0; i < ss->ovfl_next; ++i) + if (ss->ovfl[i] != NULL) + WT_RET(__slvg_trk_free(session, &ss->ovfl[i], 0)); + __wt_free(session, ss->ovfl); + + return (0); +} + +/* + * __slvg_trk_free_addr -- + * Discard address information. + */ +static void +__slvg_trk_free_addr(WT_SESSION_IMPL *session, WT_TRACK *trk) +{ + uint32_t i; + + if (trk->trk_ovfl_addr != NULL) { + for (i = 0; i < trk->trk_ovfl_cnt; ++i) + __wt_free(session, trk->trk_ovfl_addr[i].addr); + __wt_free(session, trk->trk_ovfl_addr); + } +} + +/* + * __slvg_trk_free_block -- + * Discard underlying blocks. + */ +static int +__slvg_trk_free_block(WT_SESSION_IMPL *session, WT_TRACK *trk) +{ + WT_BM *bm; + + bm = S2BT(session)->bm; + + /* + * If freeing underlying file blocks or overflow pages, this is a page + * we were tracking but eventually decided not to use. + */ + WT_RET(__wt_verbose(session, WT_VERB_SALVAGE, + "%s blocks discarded: discard freed file bytes %" PRIu32, + __wt_addr_string(session, + trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1), trk->trk_size)); + + return (bm->free(bm, session, trk->trk_addr, trk->trk_addr_size)); +} + +/* + * __slvg_trk_free -- + * Discard a WT_TRACK structure and (optionally) its underlying blocks. + */ +static int +__slvg_trk_free(WT_SESSION_IMPL *session, WT_TRACK **trkp, int free_on_last_ref) +{ + WT_TRACK *trk; + + trk = *trkp; + *trkp = NULL; + + /* + * If we're the last user of shared information, clean up. + */ + WT_ASSERT(session, trk->shared->ref > 0); + if (--trk->shared->ref == 0) { + /* + * If the free-on-last-ref flag is set, this chunk isn't going + * to use the backing physical blocks. As we're the last user + * of those blocks, nobody is going to use them and they can be + * discarded. + */ + if (free_on_last_ref) + WT_RET(__slvg_trk_free_block(session, trk)); + + __wt_free(session, trk->trk_addr); + + __slvg_trk_free_addr(session, trk); + + __wt_free(session, trk->trk_ovfl_slot); + + __wt_free(session, trk->shared); + } + + if (trk->ss->page_type == WT_PAGE_ROW_LEAF) { + __wt_buf_free(session, &trk->row_start); + __wt_buf_free(session, &trk->row_stop); + } + + __wt_free(session, trk); + + return (0); +} |