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btrfs: scrub: fix subpage repair error caused by hard coded PAGE_SIZE
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[BUG]
For the following file layout, scrub will not be able to repair all
these two repairable error, but in fact make one corruption even
unrepairable:

	  inode offset 0      4k     8K
Mirror 1               |XXXXXX|      |
Mirror 2               |      |XXXXXX|

[CAUSE]
The root cause is the hard coded PAGE_SIZE, which makes scrub repair to
go crazy for subpage.

For above case, when reading the first sector, we use PAGE_SIZE other
than sectorsize to read, which makes us to read the full range [0, 64K).
In fact, after 8K there may be no data at all, we can just get some
garbage.

Then when doing the repair, we also writeback a full page from mirror 2,
this means, we will also writeback the corrupted data in mirror 2 back
to mirror 1, leaving the range [4K, 8K) unrepairable.

[FIX]
This patch will modify the following PAGE_SIZE use with sectorsize:

- scrub_print_warning_inode()
  Remove the min() and replace PAGE_SIZE with sectorsize.
  The min() makes no sense, as csum is done for the full sector with
  padding.

  This fixes a bug that subpage report extra length like:
   checksum error at logical 298844160 on dev /dev/mapper/arm_nvme-test,
   physical 575668224, root 5, inode 257, offset 0, length 12288, links 1 (path: file)

  Where the error is only 1 sector.

- scrub_handle_errored_block()
  Comments with PAGE|page involved, all changed to sector.

- scrub_setup_recheck_block()
- scrub_repair_page_from_good_copy()
- scrub_add_page_to_wr_bio()
- scrub_wr_submit()
- scrub_add_page_to_rd_bio()
- scrub_block_complete()
  Replace PAGE_SIZE with sectorsize.
  This solves several problems where we read/write extra range for
  subpage case.

RAID56 code is excluded intentionally, as RAID56 has extra PAGE_SIZE
usage, and is not really safe enough.
Thus we will reject RAID56 for subpage in later commit.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Qu Wenruo authored and David Sterba committed Jun 21, 2021
1 parent ec87b42 commit 8df507c
Showing 1 changed file with 42 additions and 40 deletions.
82 changes: 42 additions & 40 deletions fs/btrfs/scrub.c
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Original file line number Diff line number Diff line change
Expand Up @@ -631,7 +631,6 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
void *warn_ctx)
{
u64 isize;
u32 nlink;
int ret;
int i;
Expand Down Expand Up @@ -667,7 +666,6 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
eb = swarn->path->nodes[0];
inode_item = btrfs_item_ptr(eb, swarn->path->slots[0],
struct btrfs_inode_item);
isize = btrfs_inode_size(eb, inode_item);
nlink = btrfs_inode_nlink(eb, inode_item);
btrfs_release_path(swarn->path);

Expand Down Expand Up @@ -696,12 +694,12 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
*/
for (i = 0; i < ipath->fspath->elem_cnt; ++i)
btrfs_warn_in_rcu(fs_info,
"%s at logical %llu on dev %s, physical %llu, root %llu, inode %llu, offset %llu, length %llu, links %u (path: %s)",
"%s at logical %llu on dev %s, physical %llu, root %llu, inode %llu, offset %llu, length %u, links %u (path: %s)",
swarn->errstr, swarn->logical,
rcu_str_deref(swarn->dev->name),
swarn->physical,
root, inum, offset,
min(isize - offset, (u64)PAGE_SIZE), nlink,
fs_info->sectorsize, nlink,
(char *)(unsigned long)ipath->fspath->val[i]);

btrfs_put_root(local_root);
Expand Down Expand Up @@ -890,25 +888,25 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
* read all mirrors one after the other. This includes to
* re-read the extent or metadata block that failed (that was
* the cause that this fixup code is called) another time,
* page by page this time in order to know which pages
* sector by sector this time in order to know which sectors
* caused I/O errors and which ones are good (for all mirrors).
* It is the goal to handle the situation when more than one
* mirror contains I/O errors, but the errors do not
* overlap, i.e. the data can be repaired by selecting the
* pages from those mirrors without I/O error on the
* particular pages. One example (with blocks >= 2 * PAGE_SIZE)
* would be that mirror #1 has an I/O error on the first page,
* the second page is good, and mirror #2 has an I/O error on
* the second page, but the first page is good.
* Then the first page of the first mirror can be repaired by
* taking the first page of the second mirror, and the
* second page of the second mirror can be repaired by
* copying the contents of the 2nd page of the 1st mirror.
* One more note: if the pages of one mirror contain I/O
* sectors from those mirrors without I/O error on the
* particular sectors. One example (with blocks >= 2 * sectorsize)
* would be that mirror #1 has an I/O error on the first sector,
* the second sector is good, and mirror #2 has an I/O error on
* the second sector, but the first sector is good.
* Then the first sector of the first mirror can be repaired by
* taking the first sector of the second mirror, and the
* second sector of the second mirror can be repaired by
* copying the contents of the 2nd sector of the 1st mirror.
* One more note: if the sectors of one mirror contain I/O
* errors, the checksum cannot be verified. In order to get
* the best data for repairing, the first attempt is to find
* a mirror without I/O errors and with a validated checksum.
* Only if this is not possible, the pages are picked from
* Only if this is not possible, the sectors are picked from
* mirrors with I/O errors without considering the checksum.
* If the latter is the case, at the end, the checksum of the
* repaired area is verified in order to correctly maintain
Expand Down Expand Up @@ -1065,26 +1063,26 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)

/*
* In case of I/O errors in the area that is supposed to be
* repaired, continue by picking good copies of those pages.
* Select the good pages from mirrors to rewrite bad pages from
* repaired, continue by picking good copies of those sectors.
* Select the good sectors from mirrors to rewrite bad sectors from
* the area to fix. Afterwards verify the checksum of the block
* that is supposed to be repaired. This verification step is
* only done for the purpose of statistic counting and for the
* final scrub report, whether errors remain.
* A perfect algorithm could make use of the checksum and try
* all possible combinations of pages from the different mirrors
* all possible combinations of sectors from the different mirrors
* until the checksum verification succeeds. For example, when
* the 2nd page of mirror #1 faces I/O errors, and the 2nd page
* the 2nd sector of mirror #1 faces I/O errors, and the 2nd sector
* of mirror #2 is readable but the final checksum test fails,
* then the 2nd page of mirror #3 could be tried, whether now
* then the 2nd sector of mirror #3 could be tried, whether now
* the final checksum succeeds. But this would be a rare
* exception and is therefore not implemented. At least it is
* avoided that the good copy is overwritten.
* A more useful improvement would be to pick the sectors
* without I/O error based on sector sizes (512 bytes on legacy
* disks) instead of on PAGE_SIZE. Then maybe 512 byte of one
* disks) instead of on sectorsize. Then maybe 512 byte of one
* mirror could be repaired by taking 512 byte of a different
* mirror, even if other 512 byte sectors in the same PAGE_SIZE
* mirror, even if other 512 byte sectors in the same sectorsize
* area are unreadable.
*/
success = 1;
Expand Down Expand Up @@ -1265,7 +1263,7 @@ static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
{
struct scrub_ctx *sctx = original_sblock->sctx;
struct btrfs_fs_info *fs_info = sctx->fs_info;
u64 length = original_sblock->page_count * PAGE_SIZE;
u64 length = original_sblock->page_count * fs_info->sectorsize;
u64 logical = original_sblock->pagev[0]->logical;
u64 generation = original_sblock->pagev[0]->generation;
u64 flags = original_sblock->pagev[0]->flags;
Expand All @@ -1288,13 +1286,13 @@ static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
*/

while (length > 0) {
sublen = min_t(u64, length, PAGE_SIZE);
sublen = min_t(u64, length, fs_info->sectorsize);
mapped_length = sublen;
bbio = NULL;

/*
* with a length of PAGE_SIZE, each returned stripe
* represents one mirror
* With a length of sectorsize, each returned stripe represents
* one mirror
*/
btrfs_bio_counter_inc_blocked(fs_info);
ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS,
Expand Down Expand Up @@ -1485,7 +1483,7 @@ static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
bio = btrfs_io_bio_alloc(1);
bio_set_dev(bio, spage->dev->bdev);

bio_add_page(bio, spage->page, PAGE_SIZE, 0);
bio_add_page(bio, spage->page, fs_info->sectorsize, 0);
bio->bi_iter.bi_sector = spage->physical >> 9;
bio->bi_opf = REQ_OP_READ;

Expand Down Expand Up @@ -1549,6 +1547,7 @@ static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
struct scrub_page *spage_bad = sblock_bad->pagev[page_num];
struct scrub_page *spage_good = sblock_good->pagev[page_num];
struct btrfs_fs_info *fs_info = sblock_bad->sctx->fs_info;
const u32 sectorsize = fs_info->sectorsize;

BUG_ON(spage_bad->page == NULL);
BUG_ON(spage_good->page == NULL);
Expand All @@ -1568,8 +1567,8 @@ static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
bio->bi_iter.bi_sector = spage_bad->physical >> 9;
bio->bi_opf = REQ_OP_WRITE;

ret = bio_add_page(bio, spage_good->page, PAGE_SIZE, 0);
if (PAGE_SIZE != ret) {
ret = bio_add_page(bio, spage_good->page, sectorsize, 0);
if (ret != sectorsize) {
bio_put(bio);
return -EIO;
}
Expand Down Expand Up @@ -1647,6 +1646,7 @@ static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx,
{
struct scrub_bio *sbio;
int ret;
const u32 sectorsize = sctx->fs_info->sectorsize;

mutex_lock(&sctx->wr_lock);
again:
Expand Down Expand Up @@ -1686,16 +1686,16 @@ static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx,
bio->bi_iter.bi_sector = sbio->physical >> 9;
bio->bi_opf = REQ_OP_WRITE;
sbio->status = 0;
} else if (sbio->physical + sbio->page_count * PAGE_SIZE !=
} else if (sbio->physical + sbio->page_count * sectorsize !=
spage->physical_for_dev_replace ||
sbio->logical + sbio->page_count * PAGE_SIZE !=
sbio->logical + sbio->page_count * sectorsize !=
spage->logical) {
scrub_wr_submit(sctx);
goto again;
}

ret = bio_add_page(sbio->bio, spage->page, PAGE_SIZE, 0);
if (ret != PAGE_SIZE) {
ret = bio_add_page(sbio->bio, spage->page, sectorsize, 0);
if (ret != sectorsize) {
if (sbio->page_count < 1) {
bio_put(sbio->bio);
sbio->bio = NULL;
Expand Down Expand Up @@ -1734,7 +1734,8 @@ static void scrub_wr_submit(struct scrub_ctx *sctx)
btrfsic_submit_bio(sbio->bio);

if (btrfs_is_zoned(sctx->fs_info))
sctx->write_pointer = sbio->physical + sbio->page_count * PAGE_SIZE;
sctx->write_pointer = sbio->physical + sbio->page_count *
sctx->fs_info->sectorsize;
}

static void scrub_wr_bio_end_io(struct bio *bio)
Expand Down Expand Up @@ -2072,6 +2073,7 @@ static int scrub_add_page_to_rd_bio(struct scrub_ctx *sctx,
{
struct scrub_block *sblock = spage->sblock;
struct scrub_bio *sbio;
const u32 sectorsize = sctx->fs_info->sectorsize;
int ret;

again:
Expand Down Expand Up @@ -2110,18 +2112,18 @@ static int scrub_add_page_to_rd_bio(struct scrub_ctx *sctx,
bio->bi_iter.bi_sector = sbio->physical >> 9;
bio->bi_opf = REQ_OP_READ;
sbio->status = 0;
} else if (sbio->physical + sbio->page_count * PAGE_SIZE !=
} else if (sbio->physical + sbio->page_count * sectorsize !=
spage->physical ||
sbio->logical + sbio->page_count * PAGE_SIZE !=
sbio->logical + sbio->page_count * sectorsize !=
spage->logical ||
sbio->dev != spage->dev) {
scrub_submit(sctx);
goto again;
}

sbio->pagev[sbio->page_count] = spage;
ret = bio_add_page(sbio->bio, spage->page, PAGE_SIZE, 0);
if (ret != PAGE_SIZE) {
ret = bio_add_page(sbio->bio, spage->page, sectorsize, 0);
if (ret != sectorsize) {
if (sbio->page_count < 1) {
bio_put(sbio->bio);
sbio->bio = NULL;
Expand Down Expand Up @@ -2464,7 +2466,7 @@ static void scrub_block_complete(struct scrub_block *sblock)
if (sblock->sparity && corrupted && !sblock->data_corrected) {
u64 start = sblock->pagev[0]->logical;
u64 end = sblock->pagev[sblock->page_count - 1]->logical +
PAGE_SIZE;
sblock->sctx->fs_info->sectorsize;

ASSERT(end - start <= U32_MAX);
scrub_parity_mark_sectors_error(sblock->sparity,
Expand Down

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