Subvolume iteration has a window between when we get a root ref (with
BTRFS_IOC_TREE_SEARCH or BTRFS_IOC_GET_SUBVOL_ROOTREF) and when we look
up the path of the parent directory (with BTRFS_IOC_INO_LOOKUP{,_USER}).
If the subvolume is moved or deleted and its old parent directory is
deleted during that window, then BTRFS_IOC_INO_LOOKUP{,_USER} will fail
with ENOENT. The iteration will then fail with ENOENT as well.
We originally encountered this bug with an application that called
`btrfs subvolume show` (which iterates subvolumes to find snapshots) in
parallel with other threads creating and deleting subvolumes. It can be
reproduced almost instantly with the included test cases.
Subvolume iteration should be robust against concurrent modifications to
subvolumes. So, if a subvolume's parent directory no longer exists, just
skip the subvolume, as it must have been deleted or moved elsewhere.
Reviewed-by: Neal Gompa <ngompa13@gmail.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Some upcoming tests will need to create a second Btrfs filesystem, so
add support for this to the test helpers.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
These will be used for testing some upcoming changes which allow
unprivileged operations.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
These were broken when the patch series got shuffled around.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The C libbtrfsutil library isn't very useful for scripting, so we also
want bindings for Python. Writing unit tests in Python is also much
easier than doing so in C. Only Python 3 is supported; if someone really
wants Python 2 support, they can write their own bindings. This commit
is just the scaffolding.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Omar Sandoval