提交 a13467ee 编写于 作者: Q Qu Wenruo 提交者: David Sterba

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: NQu Wenruo <wqu@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>
上级 d483bfd2
......@@ -233,7 +233,7 @@ static int scrub_sectors(struct scrub_ctx *sctx, u64 logical, u32 len,
static void scrub_bio_end_io(struct bio *bio);
static void scrub_bio_end_io_worker(struct work_struct *work);
static void scrub_block_complete(struct scrub_block *sblock);
static void scrub_remap_extent(struct btrfs_fs_info *fs_info,
static void scrub_find_good_copy(struct btrfs_fs_info *fs_info,
u64 extent_logical, u32 extent_len,
u64 *extent_physical,
struct btrfs_device **extent_dev,
......@@ -2187,7 +2187,7 @@ static void scrub_missing_raid56_pages(struct scrub_block *sblock)
* We shouldn't be scrubbing a missing device. Even for dev
* replace, we should only get here for RAID 5/6. We either
* managed to mount something with no mirrors remaining or
* there's a bug in scrub_remap_extent()/btrfs_map_block().
* there's a bug in scrub_find_good_copy()/btrfs_map_block().
*/
goto bioc_out;
}
......@@ -2510,8 +2510,11 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u8 *csum)
static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
u64 logical, u32 len,
u64 physical, struct btrfs_device *dev, u64 flags,
u64 gen, int mirror_num, u64 physical_for_dev_replace)
u64 gen, int mirror_num)
{
struct btrfs_device *src_dev = dev;
u64 src_physical = physical;
int src_mirror = mirror_num;
int ret;
u8 csum[BTRFS_CSUM_SIZE];
u32 blocksize;
......@@ -2539,6 +2542,18 @@ static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
WARN_ON(1);
}
/*
* For dev-replace case, we can have @dev being a missing device.
* Regular scrub will avoid its execution on missing device at all,
* as that would trigger tons of read error.
*
* Reading from missing device will cause read error counts to
* increase unnecessarily.
* So here we change the read source to a good mirror.
*/
if (sctx->is_dev_replace && !dev->bdev)
scrub_find_good_copy(sctx->fs_info, logical, len, &src_physical,
&src_dev, &src_mirror);
while (len) {
u32 l = min(len, blocksize);
int have_csum = 0;
......@@ -2549,15 +2564,15 @@ static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
if (have_csum == 0)
++sctx->stat.no_csum;
}
ret = scrub_sectors(sctx, logical, l, physical, dev, flags, gen,
mirror_num, have_csum ? csum : NULL,
physical_for_dev_replace);
ret = scrub_sectors(sctx, logical, l, src_physical, src_dev,
flags, gen, src_mirror,
have_csum ? csum : NULL, physical);
if (ret)
return ret;
len -= l;
logical += l;
physical += l;
physical_for_dev_replace += l;
src_physical += l;
}
return 0;
}
......@@ -3244,14 +3259,11 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
path.skip_locking = 1;
/* Go through each extent items inside the logical range */
while (cur_logical < logical_end) {
int cur_mirror = mirror_num;
struct btrfs_device *target_dev = device;
u64 extent_start;
u64 extent_len;
u64 extent_flags;
u64 extent_gen;
u64 scrub_len;
u64 cur_physical;
/* Canceled? */
if (atomic_read(&fs_info->scrub_cancel_req) ||
......@@ -3307,11 +3319,7 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
scrub_len = min(min(extent_start + extent_len,
logical_end), cur_logical + max_length) -
cur_logical;
cur_physical = cur_logical - logical_start + physical;
if (sctx->is_dev_replace)
scrub_remap_extent(fs_info, cur_logical, scrub_len,
&cur_physical, &target_dev, &cur_mirror);
if (extent_flags & BTRFS_EXTENT_FLAG_DATA) {
ret = btrfs_lookup_csums_range(csum_root, cur_logical,
cur_logical + scrub_len - 1,
......@@ -3331,10 +3339,10 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
cur_logical += scrub_len;
continue;
}
ret = scrub_extent(sctx, map, cur_logical, scrub_len, cur_physical,
target_dev, extent_flags, extent_gen,
cur_mirror, cur_logical - logical_start +
physical);
ret = scrub_extent(sctx, map, cur_logical, scrub_len,
cur_logical - logical_start + physical,
device, extent_flags, extent_gen,
mirror_num);
scrub_free_csums(sctx);
if (ret)
break;
......@@ -4342,7 +4350,7 @@ int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
return dev ? (sctx ? 0 : -ENOTCONN) : -ENODEV;
}
static void scrub_remap_extent(struct btrfs_fs_info *fs_info,
static void scrub_find_good_copy(struct btrfs_fs_info *fs_info,
u64 extent_logical, u32 extent_len,
u64 *extent_physical,
struct btrfs_device **extent_dev,
......
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