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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2008-2011 WiredTiger, Inc.
* All rights reserved.
*/
#include "wt_internal.h"
/*
* __wt_block_salvage_start --
* Start a file salvage.
*/
int
__wt_block_salvage_start(WT_SESSION_IMPL *session, WT_BLOCK *block)
{
off_t len;
uint32_t allocsize;
/*
* Truncate the file to an initial sector plus N allocation size
* units (bytes trailing the last multiple of an allocation size
* unit must be garbage, by definition).
*/
if (block->fh->file_size > WT_BLOCK_DESC_SECTOR) {
allocsize = block->allocsize;
len = block->fh->file_size - WT_BLOCK_DESC_SECTOR;
len = (len / allocsize) * allocsize;
len += WT_BLOCK_DESC_SECTOR;
if (len != block->fh->file_size)
WT_RET(__wt_ftruncate(session, block->fh, len));
}
/* Reset the description sector. */
WT_RET(__wt_desc_init(session, block->fh));
/* The first sector of the file is the description record, skip it. */
block->slvg_off = WT_BLOCK_DESC_SECTOR;
/*
* We don't currently need to do anything about the freelist because
* we don't read it for salvage operations.
*/
return (0);
}
/*
* __wt_block_salvage_end --
* End a file salvage.
*/
int
__wt_block_salvage_end(WT_SESSION_IMPL *session, WT_BLOCK *block, int success)
{
/*
* If not successful, discard the free-list, it's not useful, and
* don't write back an updated description block.
*/
if (!success) {
F_CLR(block, WT_BLOCK_OK);
__wt_block_discard(session, block);
}
return (0);
}
/*
* __wt_block_salvage_next --
* Return the next block from the file.
*/
int
__wt_block_salvage_next(
WT_SESSION_IMPL *session, WT_BLOCK *block, WT_BUF *buf,
uint8_t *addr, uint32_t *addr_sizep, uint64_t *write_genp, int *eofp)
{
WT_BLOCK_HEADER *blk;
WT_FH *fh;
off_t max, offset;
uint32_t allocsize, cksum, size;
uint8_t *endp;
*eofp = 0;
offset = block->slvg_off;
fh = block->fh;
allocsize = block->allocsize;
WT_RET(__wt_buf_initsize(session, buf, allocsize));
/* Read through the file, looking for pages with valid checksums. */
for (max = fh->file_size;;) {
if (offset >= max) { /* Check eof. */
*eofp = 1;
return (0);
}
/*
* Read the start of a possible page (an allocation-size block),
* and get a page length from it.
*/
WT_RET(__wt_read(session, fh, offset, allocsize, buf->mem));
blk = WT_BLOCK_HEADER_REF(buf->mem);
/*
* The page can't be more than the min/max page size, or past
* the end of the file.
*/
size = blk->disk_size;
cksum = blk->cksum;
if (size == 0 ||
size % allocsize != 0 ||
size > WT_BTREE_PAGE_SIZE_MAX ||
offset + (off_t)size > max)
goto skip;
/*
* The page size isn't insane, read the entire page: reading the
* page validates the checksum and then decompresses the page as
* needed. If reading the page fails, it's probably corruption,
* we ignore this block.
*/
if (__wt_block_read(session, block, buf, offset, size, cksum)) {
skip: WT_VERBOSE(session, salvage,
"skipping %" PRIu32 "B at file offset %" PRIuMAX,
allocsize, (uintmax_t)offset);
/*
* Free the block and make sure we don't return it more
* than once.
*/
WT_RET(
__wt_block_free(session, block, offset, allocsize));
block->slvg_off = offset += allocsize;
continue;
}
/* Valid block, return to our caller. */
break;
}
/*
* Track the largest write-generation we've seen in the file so future
* writes, done after salvage completes, are preferred to these blocks.
*/
*write_genp = blk->write_gen;
if (block->write_gen < blk->write_gen)
block->write_gen = blk->write_gen;
/* Re-create the address cookie that should reference this block. */
endp = addr;
WT_RET(__wt_block_addr_to_buffer(block, &endp, offset, size, cksum));
*addr_sizep = WT_PTRDIFF32(endp, addr);
/* We're successfully returning the page, move past it. */
block->slvg_off = offset + size;
return (0);
}
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