[LU-11109] zero length xattrs handled incorrectly when xattr cache disabled or bypassed

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.12.0
• Labels: xattr
• Severity: 3
• Assignee: John Hammond
• Reporter: John Hammond

Description

When xattr caching is disabled or bypassed extended attributes with zero length values are not handled correctly:

o:~# cd /mnt/lustre
o:lustre# lctl set_param llite.*.xattr_cache=1
llite.lustre-ffff8c4ac8a60000.xattr_cache=1
o:lustre# rm -f f0
o:lustre# touch f0
o:lustre# setfattr -n user.blah f0
o:lustre# getfattr -d -m- f0
# file: f0
lustre.lov=0s0AvRCwEAAAADAAAAAAAAAAEEAAACAAAAAAAQAAEAAAADAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
trusted.link=0s3/HqEQEAAAAsAAAAAAAAAAAAAAAAAAAAABQAAAACAAAABwAAAAEAAAAAZjA=
trusted.lma=0sAAAAAAAAAAABBAAAAgAAAAMAAAAAAAAA
trusted.lov=0s0AvRCwEAAAADAAAAAAAAAAEEAAACAAAAAAAQAAEAAAADAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
trusted.version=0sDAAAAAEAAAA=
user.blah

o:lustre# lctl set_param llite.*.xattr_cache=0
llite.lustre-ffff8c4ac8a60000.xattr_cache=0
o:lustre# getfattr -d -m- f0
# file: f0
lustre.lov=0s0AvRCwEAAAADAAAAAAAAAAEEAAACAAAAAAAQAAEAAAADAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
trusted.link=0s3/HqEQEAAAAsAAAAAAAAAAAAAAAAAAAAABQAAAACAAAABwAAAAEAAAAAZjA=
trusted.lma=0sAAAAAAAAAAABBAAAAgAAAAMAAAAAAAAA
trusted.lov=0s0AvRCwEAAAADAAAAAAAAAAEEAAACAAAAAAAQAAEAAAADAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
trusted.version=0sDAAAAAEAAAA=
f0: user.blah: No such attribute

I noticed this while looking at LU-11074 but this is not the underlying cause of that bug.