On Tue, May 09, 2023 at 12:50:02PM +0100, fdmanana@kernel.org wrote:
From: Filipe Manana fdmanana@suse.com
When using the logical to ino ioctl v2, if the flag to ignore offsets of file extent items (BTRFS_LOGICAL_INO_ARGS_IGNORE_OFFSET) is given, the backref walking code ends up not returning references for all file offsets of an inode that point to the given logical bytenr. This happens since kernel 6.2, commit 6ce6ba534418 ("btrfs: use a single argument for extent offset in backref walking functions") because:
It mistakenly skipped the search for file extent items in a leaf that point to the target extent if that flag is given. Instead it should only skip the filtering done by check_extent_in_eb() - that is, it should not avoid the calls to that function (or find_extent_in_eb(), which uses it).
It was also not building a list of inode extent elements (struct extent_inode_elem) if we have multiple inode references for an extent when the ignore offset flag is given to the logical to ino ioctl - it would leave a single element, only the last one that was found.
These stem from the confusing old interface for backref walking functions where we had an extent item offset argument that was a pointer to a u64 and another boolean argument that indicated if the offset should be ignored, but the pointer could be NULL. That NULL case is used by relocation, qgroup extent accounting and fiemap, simply to avoid building the inode extent list for each reference, as it's not necessary for those use cases and therefore avoids memory allocations and some computations.
Fix this by adding a boolean argument to the backref walk context structure to indicate that the inode extent list should not be built, make relocation set that argument to true and fix the backref walking logic to skip the calls to check_extent_in_eb() and find_extent_in_eb() only if this new argument is true, instead of 'ignore_extent_item_pos' being true.
A test case for fstests will be added soon, to provide cover not only for these cases but to the logical to ino ioctl in general as well, as currently we do not have a test case for it.
Fixes: 6ce6ba534418 ("btrfs: use a single argument for extent offset in backref walking functions") Reported-by: Vladimir Panteleev git@vladimir.panteleev.md Link: https://lore.kernel.org/linux-btrfs/CAHhfkvwo=nmzrJSqZ2qMfF-rZB-ab6ahHnCD_sq... Tested-by: Vladimir Panteleev git@vladimir.panteleev.md CC: stable@vger.kernel.org # 6.2+ Signed-off-by: Filipe Manana fdmanana@suse.com
V2: Remove wrong check for a non-zero extent item offset. Apply the same logic at find_parent_nodes(), that is, search for file extent items on a leaf if the ignore flag is given - the filtering will be done later at check_extent_in_eb(). Spotted by Vladimir Panteleev in the thread mentioned above.
V3: Also fix the condition to decide if we should add an inode element to the list of inode elements built before. Also rework the fix based on that missing part.
Added to misc-next. As this is a user visible bug I'll submit it in another batch for rc2, but there will be a few days before that in case you'd need another update. Thanks.