xfs: verify extent size hint is valid in inode verifier

xfs: verify extent size hint is valid in inode verifier

There are rules for vald extent size hints. We enforce them when
applications set them, but fuzzers violate those rules and that
screws us over.

This results in alignment assertion failures when setting up
allocations such as this in direct IO:

XFS: Assertion failed: ap->length, file: fs/xfs/libxfs/xfs_bmap.c, line: 3432
....
Call Trace:
 xfs_bmap_btalloc+0x415/0x910
 xfs_bmapi_write+0x71c/0x12e0
 xfs_iomap_write_direct+0x2a9/0x420
 xfs_file_iomap_begin+0x4dc/0xa70
 iomap_apply+0x43/0x100
 iomap_file_buffered_write+0x62/0x90
 xfs_file_buffered_aio_write+0xba/0x300
 __vfs_write+0xd5/0x150
 vfs_write+0xb6/0x180
 ksys_write+0x45/0xa0
 do_syscall_64+0x5a/0x180
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

And from xfs_db:

core.extsize = 10380288

Which is not an integer multiple of the block size, and so violates
Rule #7 for setting extent size hints. Validate extent size hint
rules in the inode verifier to catch this.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>