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Omar Sandoval
c36cac28cb
In btrfs_submit_direct(), if we fail to allocate the btrfs_dio_private,
we complete the ordered extent range. However, we don't mark that the
range doesn't need to be cleaned up from btrfs_direct_IO() until later.
Therefore, if we fail to allocate the btrfs_dio_private, we complete the
ordered extent range twice. We could fix this by updating
unsubmitted_oe_range earlier, but it's cleaner to reorganize the code so
that creating the btrfs_dio_private and submitting the bios are
separate, and once the btrfs_dio_private is created, cleanup always
happens through the btrfs_dio_private.
The logic around unsubmitted_oe_range_end and unsubmitted_oe_range_start
is really subtle. We have the following:
1. btrfs_direct_IO sets those two to the same value.
2. When we call __blockdev_direct_IO unless
btrfs_get_blocks_direct->btrfs_get_blocks_direct_write is called to
modify unsubmitted_oe_range_start so that start < end. Cleanup
won't happen.
3. We come into btrfs_submit_direct - if it dip allocation fails we'd
return with oe_range_end now modified so cleanup will happen.
4. If we manage to allocate the dip we reset the unsubmitted range
members to be equal so that cleanup happens from
btrfs_endio_direct_write.
This 4-step logic is not really obvious, especially given it's scattered
across 3 functions.
Fixes: f28a492878 ("Btrfs: fix leaking of ordered extents after direct IO write error")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
[ add range start/end logic explanation from Nikolay ]
Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.