[LU-646] clarification of lustre fsync behavior

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.2.0, Lustre 2.1.2, Lustre 1.8.7
• Affects Version/s: Lustre 2.0.0, Lustre 1.8.6
• Severity: 3
• Bugzilla ID: 23,485
• Assignee: Lai Siyao
• Reporter: Lai Siyao

Description

NASA is asking for clarification of fsync(2) behavior with lustre.

I'll ask the general question and then break it into two parts as we believe there is a bug in one
part.

Firstly, When a user issues an fsync(2) on a regular file descriptor in their code, we do not get a
successful response unless the underlying device, be it a disk or a raid controller(possibly with
battery backed up cache) has received the write and put it either on disk or has it safely in
batter backed up cache. Correct?

Secondly, when an fsync is issued on a directory file descriptor, from the man page:

"Calling fsync() does not necessarily ensure that the entry in the directory containing the
file has also reached disk. For that an explicit fsync() on a file descriptor for the
directory is also needed."

I would assume this does not mean file metadata, correct?

When fsync is called on a directory in a lustre file system we do not get the expected result like
we do for ext3, ext4, or xfs.

Issue Links

• Trackbacks: Lustre 1.8.x known issues tracker While testing against Lustre b18 branch, we would hit known bugs which were already reported in Lustre Bugzilla https://bugzilla.lustre.org/. In order to move away from relying on Bugzilla, we would create a JIRA
• Trackbacks: Changelog 1.8 {}version 1.8.7wc1{} {}Support for networks: socklnd \any kernel supported by Lustre, qswlnd Qsnet kernel modules 5.20 and later, openiblnd IbGold 1.8.2, o2iblnd OFED 1.3, 1.4.1, 1.4.2, 1.5.1, 1.5.2, 1.5.3.1 and 1.5.3.2 gmlnd GM 2.1....
• Trackbacks: Changelog 2.1 Changes from version 2.1.1 to version 2.1.2 Server support for kernels: 2.6.18308.4.1.el5 (RHEL5) 2.6.32220.17.1.el6 (RHEL6) Client support for unpatched kernels: 2.6.18308.4.1.el5 (RHEL5) 2.6.32220.17.1....
• Trackbacks: Changelog 2.2 version 2.2.0 Support for networks: o2iblnd OFED 1.5.4 Server support for kernels: 2.6.32220.4.2.el6 (RHEL6) Client support for unpatched kernels: 2.6.18274.18.1.el5 (RHEL5) 2.6.32220.4.2.el6 (RHEL6) 2.6.32.360....