[Cluster-devel] [PATCH v3 0/4] GFS2 shrinker deadlock

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
| With the recent gl_object fixes and an additional reference counting bug
| fixed in this patch queue, these four remaining shrinker deadlock
| avoidance patches now seem ready for mainline.
| 
| As explained in the previous posting of this patch queue, when inodes
| are evicted, GFS2 currently calls into DLM.  Inode eviction can be
| triggered by memory pressure, in the context of a random user-space
| process.  If DLM happens to block in the process in question (for
| example, it that process is a fence agent), GFS2 and DLM will deadlock.
| 
| This patch queue stops GFS2 from calling into DLM on the inode evict
| path under memory pressure.  It does so by first decoupling destroying
| inodes and putting their associated glocks, which is what ends up
| calling into DLM.  Second, when under memory pressure, it moves putting
| glocks into work queue context where it cannot block DLM.  Third, when
| gfs2_drop_inode determines that an inode's link count has hit zero under
| memory pressure, it puts that inode on the delete workqueue (and keeps
| the inode in the icache) instead of causing gfs2_evict_inode to delete
| the inode immediately.  The delete workqueue will not be processed under
| memory pressure, so deleting inodes from there is safe.
| 
| Thanks,
| Andreas
| 
| Andreas Gruenbacher (4):
|   gfs2: gfs2_glock_get: Wait on freeing glocks
|   gfs2: Get rid of gfs2_set_nlink
|   gfs2: gfs2_evict_inode: Put glocks asynchronously
|   gfs2: Defer deleting inodes under memory pressure
| 
|  fs/gfs2/glock.c | 135
|  +++++++++++++++++++++++++++++++++++++++++++++++---------
|  fs/gfs2/glock.h |   2 +
|  fs/gfs2/glops.c |  28 +-----------
|  fs/gfs2/super.c |  43 +++++++++++++++++-
|  4 files changed, 157 insertions(+), 51 deletions(-)
| 
| --
| 2.13.3
| 
| 
Hi,

These all look good. This was a major problem to get fixed.
Thanks for all your effort. All four patches are now pushed to the
for-next branch of the linux-gfs2 tree:

https://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2.git/commit/fs/gfs2?h=for-next&id=56a365beda9ef5121eab1d8c5dfe8742b4e69d48
https://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2.git/commit/fs/gfs2?h=for-next&id=325c8fe97257c68c90c68cc6bde61e9825de3361
https://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2.git/commit/fs/gfs2?h=for-next&id=6e036cbbd6909b8c8e53cd399051c699379e4818
https://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2.git/commit/fs/gfs2?h=for-next&id=0d0e409c22b6b53e1ed1a57b1551e144e0afae79

Regards,

Bob Peterson
Red Hat File Systems