On 27 May 2021 at 05:49, Dave Chinner wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > 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. > The functions calling xfs_bmap_btree_to_extents() have indeed read all the extents of the corresponding inode fork into memory. Hence, removal of the assert() statement is not an issue. Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx> > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> -- chandan
