On Thu, Oct 14, 2021 at 03:05:54PM +0300, Nikolay Borisov wrote:

On 1.09.21 г. 20:00, Omar Sandoval wrote:

quoted

From: Omar Sandoval <redacted>

btrfs_csum_one_bio() loops over each filesystem block in the bio while
keeping a cursor of its current logical position in the file in order to
look up the ordered extent to add the checksums to. However, this
doesn't make much sense for compressed extents, as a sector on disk does
not correspond to a sector of decompressed file data. It happens to work
because 1) the compressed bio always covers one ordered extent and 2)
the size of the bio is always less than the size of the ordered extent.
However, the second point will not always be true for encoded writes.

Let's add a boolean parameter to btrfs_csum_one_bio() to indicate that
it can assume that the bio only covers one ordered extent. Since we're
already changing the signature, let's get rid of the contig parameter
and make it implied by the offset parameter, similar to the change we
recently made to btrfs_lookup_bio_sums(). Additionally, let's rename
nr_sectors to blockcount to make it clear that it's the number of
filesystem blocks, not the number of 512-byte sectors.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <redacted>

Code-wise this looks, though I don't know why we are guaranteed that a
compressed extent will only cover a single OE.

See submit_compressed_extents(): we always add an ordered extent that
covers the whole range that we're submitting, and then
btrfs_submit_compressed_write() creates one or more bios that are
subsets of that range.

But I trust you so:
Reviewed-by: Nikolay Borisov <redacted>

Thanks!