Dave Chinner 991c2c5980 xfs: btree format inode forks can have zero extents
xfs/538 is assert failing with this trace when testing with
directory block sizes of 64kB:

XFS: Assertion failed: !xfs_need_iread_extents(ifp), file: fs/xfs/libxfs/xfs_bmap.c, line: 608
....
Call Trace:
 xfs_bmap_btree_to_extents+0x2a9/0x470
 ? kmem_cache_alloc+0xe7/0x220
 __xfs_bunmapi+0x4ca/0xdf0
 xfs_bunmapi+0x1a/0x30
 xfs_dir2_shrink_inode+0x71/0x210
 xfs_dir2_block_to_sf+0x2ae/0x410
 xfs_dir2_block_removename+0x21a/0x280
 xfs_dir_removename+0x195/0x1d0
 xfs_remove+0x244/0x460
 xfs_vn_unlink+0x53/0xa0
 ? selinux_inode_unlink+0x13/0x20
 vfs_unlink+0x117/0x220
 do_unlinkat+0x1a2/0x2d0
 __x64_sys_unlink+0x42/0x60
 do_syscall_64+0x3a/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xae

This is a check to ensure that the extents have been read into
memory before we are doing a ifork btree manipulation. This assert
is bogus in the above case.

We have a fragmented directory block that has more extents in it
than can fit in extent format, so the inode data fork is in btree
format. xfs_dir2_shrink_inode() asks to remove all remaining 16
filesystem blocks from the inode so it can convert to short form,
and __xfs_bunmapi() removes all the extents. We now have a data fork
in btree format but have zero extents in the fork. This incorrectly
trips the xfs_need_iread_extents() assert because it assumes that an
empty extent btree means the extent tree has not been read into
memory yet. This is clearly not the case with xfs_bunmapi(), as it
has an explicit call to xfs_iread_extents() in it to pull the
extents into memory before it starts unmapping.

Also, the assert directly after this bogus one is:

	ASSERT(ifp->if_format == XFS_DINODE_FMT_BTREE);

Which covers the context in which it is legal to call
xfs_bmap_btree_to_extents just fine. Hence we should just remove the
bogus assert as it is clearly wrong and causes a regression.

The returns the test behaviour to the pre-existing assert failure in
xfs_dir2_shrink_inode() that indicates xfs_bunmapi() has failed to
remove all the extents in the range it was asked to unmap.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
2021-05-27 08:11:24 -07:00
2021-05-07 00:26:34 -07:00
2021-05-14 19:41:32 -07:00
2021-05-16 15:27:44 -07:00

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.
Description
No description provided
Readme 3.4 GiB
Languages
C 97%
Assembly 1%
Shell 0.6%
Rust 0.5%
Python 0.4%
Other 0.3%