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/*-
* Copyright (c) 2014-2020 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
/*
* WiredTiger's block manager interface.
*/
/*
* The file's description is written into the first block of the file, which means we can use an
* offset of 0 as an invalid offset.
*/
#define WT_BLOCK_INVALID_OFFSET 0
/*
* The block manager maintains three per-checkpoint extent lists:
* alloc: the extents allocated in this checkpoint
* avail: the extents available for allocation
* discard: the extents freed in this checkpoint
*
* An extent list is based on two skiplists: first, a by-offset list linking
* WT_EXT elements and sorted by file offset (low-to-high), second, a by-size
* list linking WT_SIZE elements and sorted by chunk size (low-to-high).
*
* Additionally, each WT_SIZE element on the by-size has a skiplist of its own,
* linking WT_EXT elements and sorted by file offset (low-to-high). This list
* has an entry for extents of a particular size.
*
* The trickiness is each individual WT_EXT element appears on two skiplists.
* In order to minimize allocation calls, we allocate a single array of WT_EXT
* pointers at the end of the WT_EXT structure, for both skiplists, and store
* the depth of the skiplist in the WT_EXT structure. The skiplist entries for
* the offset skiplist start at WT_EXT.next[0] and the entries for the size
* skiplist start at WT_EXT.next[WT_EXT.depth].
*
* One final complication: we only maintain the per-size skiplist for the avail
* list, the alloc and discard extent lists are not searched based on size.
*/
/*
* WT_EXTLIST --
* An extent list.
*/
struct __wt_extlist {
char *name; /* Name */
uint64_t bytes; /* Byte count */
uint32_t entries; /* Entry count */
uint32_t logid; /* Written log ID */
wt_off_t offset; /* Written extent offset */
uint32_t checksum; /* Written extent checksum */
uint32_t size; /* Written extent size */
bool track_size; /* Maintain per-size skiplist */
WT_EXT *last; /* Cached last element */
WT_EXT *off[WT_SKIP_MAXDEPTH]; /* Size/offset skiplists */
WT_SIZE *sz[WT_SKIP_MAXDEPTH];
};
/*
* WT_EXT --
* Encapsulation of an extent, either allocated or freed within the
* checkpoint.
*/
struct __wt_ext {
wt_off_t off; /* Extent's file offset */
wt_off_t size; /* Extent's Size */
uint8_t depth; /* Skip list depth */
/*
* Variable-length array, sized by the number of skiplist elements. The first depth array
* entries are the address skiplist elements, the second depth array entries are the size
* skiplist.
*/
WT_EXT *next[0]; /* Offset, size skiplists */
};
/*
* WT_SIZE --
* Encapsulation of a block size skiplist entry.
*/
struct __wt_size {
wt_off_t size; /* Size */
uint8_t depth; /* Skip list depth */
WT_EXT *off[WT_SKIP_MAXDEPTH]; /* Per-size offset skiplist */
/*
* We don't use a variable-length array for the size skiplist, we want to be able to use any
* cached WT_SIZE structure as the head of a list, and we don't know the related WT_EXT
* structure's depth.
*/
WT_SIZE *next[WT_SKIP_MAXDEPTH]; /* Size skiplist */
};
/*
* WT_EXT_FOREACH --
* Walk a block manager skiplist.
* WT_EXT_FOREACH_OFF --
* Walk a block manager skiplist where the WT_EXT.next entries are offset
* by the depth.
*/
#define WT_EXT_FOREACH(skip, head) \
for ((skip) = (head)[0]; (skip) != NULL; (skip) = (skip)->next[0])
#define WT_EXT_FOREACH_OFF(skip, head) \
for ((skip) = (head)[0]; (skip) != NULL; (skip) = (skip)->next[(skip)->depth])
/*
* Checkpoint cookie: carries a version number as I don't want to rev the schema
* file version should the default block manager checkpoint format change.
*
* Version #1 checkpoint cookie format:
* [1] [root addr] [alloc addr] [avail addr] [discard addr]
* [file size] [checkpoint size] [write generation]
*/
#define WT_BM_CHECKPOINT_VERSION 1 /* Checkpoint format version */
#define WT_BLOCK_EXTLIST_MAGIC 71002 /* Identify a list */
/*
* There are two versions of the extent list blocks: the original, and a second version where
* current checkpoint information is appended to the avail extent list.
*/
#define WT_BLOCK_EXTLIST_VERSION_ORIG 0 /* Original version */
#define WT_BLOCK_EXTLIST_VERSION_CKPT 1 /* Checkpoint in avail output */
/*
* Maximum buffer required to store a checkpoint: 1 version byte followed by
* 14 packed 8B values.
*/
#define WT_BLOCK_CHECKPOINT_BUFFER (1 + 14 * WT_INTPACK64_MAXSIZE)
struct __wt_block_ckpt {
uint8_t version; /* Version */
uint32_t root_logid;
wt_off_t root_offset; /* The root */
uint32_t root_checksum, root_size;
WT_EXTLIST alloc; /* Extents allocated */
WT_EXTLIST avail; /* Extents available */
WT_EXTLIST discard; /* Extents discarded */
wt_off_t file_size; /* Checkpoint file size */
uint64_t ckpt_size; /* Checkpoint byte count */
WT_EXTLIST ckpt_avail; /* Checkpoint free'd extents */
/*
* Checkpoint archive: the block manager may potentially free a lot of memory from the
* allocation and discard extent lists when checkpoint completes. Put it off until the
* checkpoint resolves, that lets the upper btree layer continue eviction sooner.
*/
WT_EXTLIST ckpt_alloc; /* Checkpoint archive */
WT_EXTLIST ckpt_discard; /* Checkpoint archive */
};
/*
* WT_BM --
* Block manager handle, references a single checkpoint in a file.
*/
struct __wt_bm {
/* Methods */
int (*addr_invalid)(WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t);
int (*addr_string)(WT_BM *, WT_SESSION_IMPL *, WT_ITEM *, const uint8_t *, size_t);
u_int (*block_header)(WT_BM *);
int (*checkpoint)(WT_BM *, WT_SESSION_IMPL *, WT_ITEM *, WT_CKPT *, bool);
int (*checkpoint_last)(WT_BM *, WT_SESSION_IMPL *, char **, char **, WT_ITEM *);
int (*checkpoint_load)(
WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t, uint8_t *, size_t *, bool);
int (*checkpoint_resolve)(WT_BM *, WT_SESSION_IMPL *, bool);
int (*checkpoint_start)(WT_BM *, WT_SESSION_IMPL *);
int (*checkpoint_unload)(WT_BM *, WT_SESSION_IMPL *);
int (*close)(WT_BM *, WT_SESSION_IMPL *);
int (*compact_end)(WT_BM *, WT_SESSION_IMPL *);
int (*compact_page_skip)(WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t, bool *);
int (*compact_skip)(WT_BM *, WT_SESSION_IMPL *, bool *);
int (*compact_start)(WT_BM *, WT_SESSION_IMPL *);
int (*corrupt)(WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t);
int (*free)(WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t);
bool (*is_mapped)(WT_BM *, WT_SESSION_IMPL *);
int (*map_discard)(WT_BM *, WT_SESSION_IMPL *, void *, size_t);
int (*preload)(WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t);
int (*read)(WT_BM *, WT_SESSION_IMPL *, WT_ITEM *, const uint8_t *, size_t);
int (*salvage_end)(WT_BM *, WT_SESSION_IMPL *);
int (*salvage_next)(WT_BM *, WT_SESSION_IMPL *, uint8_t *, size_t *, bool *);
int (*salvage_start)(WT_BM *, WT_SESSION_IMPL *);
int (*salvage_valid)(WT_BM *, WT_SESSION_IMPL *, uint8_t *, size_t, bool);
int (*size)(WT_BM *, WT_SESSION_IMPL *, wt_off_t *);
int (*stat)(WT_BM *, WT_SESSION_IMPL *, WT_DSRC_STATS *stats);
int (*sync)(WT_BM *, WT_SESSION_IMPL *, bool);
int (*verify_addr)(WT_BM *, WT_SESSION_IMPL *, const uint8_t *, size_t);
int (*verify_end)(WT_BM *, WT_SESSION_IMPL *);
int (*verify_start)(WT_BM *, WT_SESSION_IMPL *, WT_CKPT *, const char *[]);
int (*write)(WT_BM *, WT_SESSION_IMPL *, WT_ITEM *, uint8_t *, size_t *, bool, bool);
int (*write_size)(WT_BM *, WT_SESSION_IMPL *, size_t *);
WT_BLOCK *block; /* Underlying file */
void *map; /* Mapped region */
size_t maplen;
void *mapped_cookie;
/*
* There's only a single block manager handle that can be written, all others are checkpoints.
*/
bool is_live; /* The live system */
};
/*
* WT_BLOCK --
* Block manager handle, references a single file.
*/
struct __wt_block {
const char *name; /* Name */
uint64_t name_hash; /* Hash of name */
/* A list of block manager handles, sharing a file descriptor. */
uint32_t ref; /* References */
TAILQ_ENTRY(__wt_block) q; /* Linked list of handles */
TAILQ_ENTRY(__wt_block) hashq; /* Hashed list of handles */
WT_FH *fh; /* Backing file handle */
wt_off_t size; /* File size */
wt_off_t extend_size; /* File extended size */
wt_off_t extend_len; /* File extend chunk size */
bool created_during_backup; /* Created during incremental backup */
/* Configuration information, set when the file is opened. */
uint32_t allocfirst; /* Allocation is first-fit */
uint32_t allocsize; /* Allocation size */
bool log_structured; /* Write checkpoint as separate files */
size_t os_cache; /* System buffer cache flush max */
size_t os_cache_max;
size_t os_cache_dirty_max;
u_int block_header; /* Header length */
/* Log-structured tracking. */
uint32_t file_flags, logid, max_logid;
WT_FH **lfh;
size_t lfh_alloc;
/*
* There is only a single checkpoint in a file that can be written. The information could
* logically live in the WT_BM structure, but then we would be re-creating it every time we
* opened a new checkpoint and I'd rather not do that. So, it's stored here, only accessed by
* one WT_BM handle.
*/
WT_SPINLOCK live_lock; /* Live checkpoint lock */
WT_BLOCK_CKPT live; /* Live checkpoint */
#ifdef HAVE_DIAGNOSTIC
bool live_open; /* Live system is open */
#endif
/* Live checkpoint status */
enum {
WT_CKPT_NONE = 0,
WT_CKPT_INPROGRESS,
WT_CKPT_PANIC_ON_FAILURE,
WT_CKPT_SALVAGE
} ckpt_state;
WT_CKPT *final_ckpt; /* Final live checkpoint write */
/* Compaction support */
int compact_pct_tenths; /* Percent to compact */
uint64_t compact_pages_reviewed; /* Pages reviewed */
uint64_t compact_pages_skipped; /* Pages skipped */
uint64_t compact_pages_written; /* Pages rewritten */
/* Salvage support */
wt_off_t slvg_off; /* Salvage file offset */
/* Verification support */
bool verify; /* If performing verification */
bool verify_layout; /* Print out file layout information */
bool verify_strict; /* Fail hard on any error */
wt_off_t verify_size; /* Checkpoint's file size */
WT_EXTLIST verify_alloc; /* Verification allocation list */
uint64_t frags; /* Maximum frags in the file */
uint8_t *fragfile; /* Per-file frag tracking list */
uint8_t *fragckpt; /* Per-checkpoint frag tracking list */
};
/*
* WT_BLOCK_DESC --
* The file's description.
*/
struct __wt_block_desc {
#define WT_BLOCK_MAGIC 120897
uint32_t magic; /* 00-03: Magic number */
#define WT_BLOCK_MAJOR_VERSION 1
uint16_t majorv; /* 04-05: Major version */
#define WT_BLOCK_MINOR_VERSION 0
uint16_t minorv; /* 06-07: Minor version */
uint32_t checksum; /* 08-11: Description block checksum */
uint32_t unused; /* 12-15: Padding */
};
/*
* WT_BLOCK_DESC_SIZE is the expected structure size -- we verify the build to ensure the compiler
* hasn't inserted padding (padding won't cause failure, we reserve the first allocation-size block
* of the file for this information, but it would be worth investigation, regardless).
*/
#define WT_BLOCK_DESC_SIZE 16
/*
* __wt_block_desc_byteswap --
* Handle big- and little-endian transformation of a description block.
*/
static inline void
__wt_block_desc_byteswap(WT_BLOCK_DESC *desc)
{
#ifdef WORDS_BIGENDIAN
desc->magic = __wt_bswap32(desc->magic);
desc->majorv = __wt_bswap16(desc->majorv);
desc->minorv = __wt_bswap16(desc->minorv);
desc->checksum = __wt_bswap32(desc->checksum);
#else
WT_UNUSED(desc);
#endif
}
/*
* WT_BLOCK_HEADER --
* Blocks have a common header, a WT_PAGE_HEADER structure followed by a
* block-manager specific structure: WT_BLOCK_HEADER is WiredTiger's default.
*/
struct __wt_block_header {
/*
* We write the page size in the on-disk page header because it makes salvage easier. (If we
* don't know the expected page length, we'd have to read increasingly larger chunks from the
* file until we find one that checksums, and that's going to be harsh given WiredTiger's
* potentially large page sizes.)
*/
uint32_t disk_size; /* 00-03: on-disk page size */
/*
* Page checksums are stored in two places. First, the page checksum is written within the
* internal page that references it as part of the address cookie. This is done to improve the
* chances of detecting not only disk corruption but other bugs (for example, overwriting a page
* with another valid page image). Second, a page's checksum is stored in the disk header. This
* is for salvage, so salvage knows it has found a page that may be useful.
*/
uint32_t checksum; /* 04-07: checksum */
/*
* No automatic generation: flag values cannot change, they're written to disk.
*/
#define WT_BLOCK_DATA_CKSUM 0x1u /* Block data is part of the checksum */
uint8_t flags; /* 08: flags */
/*
* End the structure with 3 bytes of padding: it wastes space, but it leaves the structure
* 32-bit aligned and having a few bytes to play with in the future can't hurt.
*/
uint8_t unused[3]; /* 09-11: unused padding */
};
/*
* WT_BLOCK_HEADER_SIZE is the number of bytes we allocate for the structure: if the compiler
* inserts padding it will break the world.
*/
#define WT_BLOCK_HEADER_SIZE 12
/*
* __wt_block_header_byteswap_copy --
* Handle big- and little-endian transformation of a header block, copying from a source to a
* target.
*/
static inline void
__wt_block_header_byteswap_copy(WT_BLOCK_HEADER *from, WT_BLOCK_HEADER *to)
{
*to = *from;
#ifdef WORDS_BIGENDIAN
to->disk_size = __wt_bswap32(from->disk_size);
to->checksum = __wt_bswap32(from->checksum);
#endif
}
/*
* __wt_block_header_byteswap --
* Handle big- and little-endian transformation of a header block.
*/
static inline void
__wt_block_header_byteswap(WT_BLOCK_HEADER *blk)
{
#ifdef WORDS_BIGENDIAN
__wt_block_header_byteswap_copy(blk, blk);
#else
WT_UNUSED(blk);
#endif
}
/*
* WT_BLOCK_HEADER_BYTE
* WT_BLOCK_HEADER_BYTE_SIZE --
* The first usable data byte on the block (past the combined headers).
*/
#define WT_BLOCK_HEADER_BYTE_SIZE (WT_PAGE_HEADER_SIZE + WT_BLOCK_HEADER_SIZE)
#define WT_BLOCK_HEADER_BYTE(dsk) ((void *)((uint8_t *)(dsk) + WT_BLOCK_HEADER_BYTE_SIZE))
/*
* We don't compress or encrypt the block's WT_PAGE_HEADER or WT_BLOCK_HEADER structures because we
* need both available with decompression or decryption. We use the WT_BLOCK_HEADER checksum and
* on-disk size during salvage to figure out where the blocks are, and we use the WT_PAGE_HEADER
* in-memory size during decompression and decryption to know how large a target buffer to allocate.
* We can only skip the header information when doing encryption, but we skip the first 64B when
* doing compression; a 64B boundary may offer better alignment for the underlying compression
* engine, and skipping 64B shouldn't make any difference in terms of compression efficiency.
*/
#define WT_BLOCK_COMPRESS_SKIP 64
#define WT_BLOCK_ENCRYPT_SKIP WT_BLOCK_HEADER_BYTE_SIZE
/*
* __wt_block_header --
* Return the size of the block-specific header.
*/
static inline u_int
__wt_block_header(WT_BLOCK *block)
{
WT_UNUSED(block);
return ((u_int)WT_BLOCK_HEADER_SIZE);
}
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