forked from Minki/linux
btrfs: scrub: move scrub_remap_extent() call into scrub_extent()
[SUSPICIOUS CODE] When refactoring scrub code, I noticed a very strange behavior around scrub_remap_extent(): if (sctx->is_dev_replace) scrub_remap_extent(fs_info, cur_logical, scrub_len, &cur_physical, &target_dev, &cur_mirror); As replace target is a 1:1 copy of the source device, thus physical offset inside the target should be the same as physical inside source, thus this remap call makes no sense to me. [REAL FUNCTIONALITY] After more investigation, the function name scrub_remap_extent() doesn't tell anything of the truth, nor does its if () condition. The real story behind this function is that, for scrub_pages() we never expect missing device, even for replacing missing device. What scrub_remap_extent() is really doing is to find a live mirror, and make later scrub_pages() to read data from the good copy, other than from the missing device and increase error counters unnecessarily. [IMPROVEMENT] We have no need to bother scrub_remap_extent() in scrub_simple_mirror() at all, we only need to call it before we call scrub_pages(). And rename the function to scrub_find_live_copy(), add extra comments on them. By this we can remove one parameter from scrub_extent(), and reduce the unnecessary calls to scrub_remap_extent() for regular replace. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo
David Sterba
parent
d483bfd27a
commit
a13467ee7a
@ -233,11 +233,11 @@ static int scrub_sectors(struct scrub_ctx *sctx, u64 logical, u32 len,
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static void scrub_bio_end_io(struct bio *bio);
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static void scrub_bio_end_io_worker(struct work_struct *work);
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static void scrub_block_complete(struct scrub_block *sblock);
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static void scrub_remap_extent(struct btrfs_fs_info *fs_info,
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u64 extent_logical, u32 extent_len,
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u64 *extent_physical,
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struct btrfs_device **extent_dev,
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int *extent_mirror_num);
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static void scrub_find_good_copy(struct btrfs_fs_info *fs_info,
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u64 extent_logical, u32 extent_len,
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u64 *extent_physical,
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struct btrfs_device **extent_dev,
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int *extent_mirror_num);
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static int scrub_add_sector_to_wr_bio(struct scrub_ctx *sctx,
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struct scrub_sector *sector);
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static void scrub_wr_submit(struct scrub_ctx *sctx);
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@ -2187,7 +2187,7 @@ static void scrub_missing_raid56_pages(struct scrub_block *sblock)
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* We shouldn't be scrubbing a missing device. Even for dev
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* replace, we should only get here for RAID 5/6. We either
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* managed to mount something with no mirrors remaining or
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* there's a bug in scrub_remap_extent()/btrfs_map_block().
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* there's a bug in scrub_find_good_copy()/btrfs_map_block().
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*/
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goto bioc_out;
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}
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@ -2510,8 +2510,11 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u8 *csum)
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static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
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u64 logical, u32 len,
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u64 physical, struct btrfs_device *dev, u64 flags,
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u64 gen, int mirror_num, u64 physical_for_dev_replace)
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u64 gen, int mirror_num)
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{
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struct btrfs_device *src_dev = dev;
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u64 src_physical = physical;
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int src_mirror = mirror_num;
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int ret;
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u8 csum[BTRFS_CSUM_SIZE];
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u32 blocksize;
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@ -2539,6 +2542,18 @@ static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
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WARN_ON(1);
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}
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/*
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* For dev-replace case, we can have @dev being a missing device.
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* Regular scrub will avoid its execution on missing device at all,
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* as that would trigger tons of read error.
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*
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* Reading from missing device will cause read error counts to
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* increase unnecessarily.
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* So here we change the read source to a good mirror.
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*/
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if (sctx->is_dev_replace && !dev->bdev)
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scrub_find_good_copy(sctx->fs_info, logical, len, &src_physical,
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&src_dev, &src_mirror);
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while (len) {
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u32 l = min(len, blocksize);
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int have_csum = 0;
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@ -2549,15 +2564,15 @@ static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
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if (have_csum == 0)
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++sctx->stat.no_csum;
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}
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ret = scrub_sectors(sctx, logical, l, physical, dev, flags, gen,
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mirror_num, have_csum ? csum : NULL,
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physical_for_dev_replace);
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ret = scrub_sectors(sctx, logical, l, src_physical, src_dev,
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flags, gen, src_mirror,
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have_csum ? csum : NULL, physical);
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if (ret)
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return ret;
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len -= l;
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logical += l;
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physical += l;
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physical_for_dev_replace += l;
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src_physical += l;
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}
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return 0;
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}
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@ -3244,14 +3259,11 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
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path.skip_locking = 1;
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/* Go through each extent items inside the logical range */
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while (cur_logical < logical_end) {
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int cur_mirror = mirror_num;
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struct btrfs_device *target_dev = device;
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u64 extent_start;
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u64 extent_len;
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u64 extent_flags;
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u64 extent_gen;
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u64 scrub_len;
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u64 cur_physical;
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/* Canceled? */
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if (atomic_read(&fs_info->scrub_cancel_req) ||
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@ -3307,11 +3319,7 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
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scrub_len = min(min(extent_start + extent_len,
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logical_end), cur_logical + max_length) -
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cur_logical;
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cur_physical = cur_logical - logical_start + physical;
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if (sctx->is_dev_replace)
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scrub_remap_extent(fs_info, cur_logical, scrub_len,
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&cur_physical, &target_dev, &cur_mirror);
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if (extent_flags & BTRFS_EXTENT_FLAG_DATA) {
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ret = btrfs_lookup_csums_range(csum_root, cur_logical,
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cur_logical + scrub_len - 1,
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@ -3331,10 +3339,10 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
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cur_logical += scrub_len;
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continue;
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}
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ret = scrub_extent(sctx, map, cur_logical, scrub_len, cur_physical,
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target_dev, extent_flags, extent_gen,
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cur_mirror, cur_logical - logical_start +
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physical);
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ret = scrub_extent(sctx, map, cur_logical, scrub_len,
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cur_logical - logical_start + physical,
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device, extent_flags, extent_gen,
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mirror_num);
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scrub_free_csums(sctx);
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if (ret)
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break;
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@ -4342,11 +4350,11 @@ int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
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return dev ? (sctx ? 0 : -ENOTCONN) : -ENODEV;
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}
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static void scrub_remap_extent(struct btrfs_fs_info *fs_info,
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u64 extent_logical, u32 extent_len,
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u64 *extent_physical,
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struct btrfs_device **extent_dev,
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int *extent_mirror_num)
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static void scrub_find_good_copy(struct btrfs_fs_info *fs_info,
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u64 extent_logical, u32 extent_len,
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u64 *extent_physical,
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struct btrfs_device **extent_dev,
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int *extent_mirror_num)
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{
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u64 mapped_length;
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struct btrfs_io_context *bioc = NULL;
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