diff options
| author | Sakshi Bansal <sabansal@redhat.com> | 2018-01-22 14:38:17 +0530 |
|---|---|---|
| committer | Raghavendra G <rgowdapp@redhat.com> | 2018-01-24 05:39:44 +0000 |
| commit | 78868033bc208bdb681266d0129e66f5627295a2 (patch) | |
| tree | 89695fbabe3cc077669b23934aac24c3f457ef3c /configure.ac | |
| parent | 5cbe21b1ddf6eae4782afa33ce841fc4aa195974 (diff) | |
dentry fop serializer: added new server side xlator for dentry fop serialization
Problems addressed by this xlator :
[1]. To prevent race between parallel mkdir,mkdir and lookup etc.
Fops like mkdir/create, lookup, rename, unlink, link that happen on a
particular dentry must be serialized to ensure atomicity.
Another possible case can be a fresh lookup to find existance of a path
whose gfid is not set yet. Further, storage/posix employs a ctime based
heuristic 'is_fresh_file' (interval time is less than 1 second of current
time) to check fresh-ness of file. With serialization of these two fops
(lookup & mkdir), we eliminate the race altogether.
[2]. Staleness of dentries
This causes exponential increase in traversal time for any inode in the
subtree of the directory pointed by stale dentry.
Cause : Stale dentry is created because of following two operations:
a. dentry creation due to inode_link, done during operations like
lookup, mkdir, create, mknod, symlink, create and
b. dentry unlinking due to various operations like rmdir, rename,
unlink.
The reason is __inode_link uses __is_dentry_cyclic, which explores
all possible path to avoid cyclic link formation during inode
linkage. __is_dentry_cyclic explores stale-dentry(ies) and its
all ancestors which is increases traversing time exponentially.
Implementation : To acheive this all fops on dentry must take entry locks
before they proceed, once they have acquired locks, they perform the fop
and then release the lock.
Some documentation from email conversation:
[1] http://www.gluster.org/pipermail/gluster-devel/2015-December/047314.html
[2] http://www.gluster.org/pipermail/gluster-devel/2015-August/046428.html
With this patch, the feature is optional, enable it by running:
`gluster volume set $volname features.sdfs enable`
Also the feature is tested for a month without issues in the
experiemental branch for all the regression.
Change-Id: I6e80ba3cabfa6facd5dda63bd482b9bf18b6b79b
Fixes: #397
BUG: 1304962
Signed-off-by: Sakshi Bansal <sabansal@redhat.com>
Signed-off-by: Amar Tumballi <amarts@redhat.com>
Signed-off-by: Sunny Kumar <sunkumar@redhat.com>
Diffstat (limited to 'configure.ac')
| -rw-r--r-- | configure.ac | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/configure.ac b/configure.ac index 81c56d4e68f..ed84c661797 100644 --- a/configure.ac +++ b/configure.ac @@ -152,6 +152,8 @@ AC_CONFIG_FILES([Makefile xlators/features/marker/src/Makefile xlators/features/selinux/Makefile xlators/features/selinux/src/Makefile + xlators/features/sdfs/Makefile + xlators/features/sdfs/src/Makefile xlators/features/read-only/Makefile xlators/features/read-only/src/Makefile xlators/features/compress/Makefile |