On 12/16/19 1:26 PM, fdmanana@xxxxxxxxxx wrote:
From: Filipe Manana <fdmanana@xxxxxxxx>
Since btrfs was migrated to use the generic VFS helpers for clone and
deduplication, it stopped allowing for the last block of a file to be
deduplicated when the source file size is not sector size aligned (when
eof is somewhere in the middle of the last block). There are two reasons
for that:
1) The generic code always rounds down, to a multiple of the block size,
the range's length for deduplications. This means we end up never
deduplicating the last block when the eof is not block size aligned,
even for the safe case where the destination range's end offset matches
the destination file's size. That rounding down operation is done at
generic_remap_check_len();
2) Because of that, the btrfs specific code does not expect anymore any
non-aligned range length's for deduplication and therefore does not
work if such nona-aligned length is given.
Does anybody else rely on this behavior that needs a change like this for their fs?
This patch addresses that second part, and it depends on a patch that
fixes generic_remap_check_len(), in the VFS, which was submitted ealier
and has the following subject:
"fs: allow deduplication of eof block into the end of the destination file"
These two patches address reports from users that started seeing lower
deduplication rates due to the last block never being deduplicated when
the file size is not aligned to the filesystem's block size.
Link: https://lore.kernel.org/linux-btrfs/2019-1576167349.500456@xxxxxxxxxxxxxx/
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Thanks,
Josef
