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authorPrashanth Pai <ppai@redhat.com>2016-05-04 16:56:50 +0530
committerRaghavendra G <rgowdapp@redhat.com>2016-05-10 02:05:38 -0700
commit0c73e7050c4d30ace0c39cc9b9634e9c1b448cfb (patch)
tree3b72d177568daa41f72d8260112857c8f67cb982 /libglusterfs/src/glusterfs.h
parentdc3b3af58281bbf63a2001e0a9a34b20cd251586 (diff)
readdir-ahead: Prefetch xattrs needed by md-cache
Problem: Negative cache feature implementation in md-cache requires xattrs returned by posix to be intercepted for every call that can possibly return xattrs. This includes readdirp(). This is crucial to treat missing keys in cache as a case of negative entry (returns ENODATA) md-cache puts names of xattrs that it wants to cache in xdata and passes it down to posix which returns the specified xattrs in the callback. This is done in lookup() and readdirp(). Hence, a xattr that is cached can be invalidated during readdirp_cbk too. This is based on the assumption that readdirp() will always return all xattrs that md-cache is interested in. However, this is not the case when readdirp() call is served from readdir-ahead's cache. readdir-ahead xlator will pre-fetch dentries during opendir_cbk and readdirp. These internal readdirp() calls made by readdir-ahead xlator does not set xdata in it's requests. Hence, no xattrs are fetched and stored in it's internal cache. This causes metadata loss in gluster-swift. md-cache returns ENODATA during getxattr() call even though the xattr for that object exists on the brick. On receiving ENODATA, gluster-swift will create new metadata and do setxattr(). This results in loss of information stored in existing xattr. Fix: During opendir, md-cache will communicate to readdir-ahead asking it to store the names of xattrs it's interested in so that readdir-ahead can fetch those in all subsequent internal readdirp() calls issued by it. This stored names of xattrs is invalidated/updated on the next real readdirp() call issued by application. This readdirp() call will have xdata set correctly by md-cache xlator. BUG: 1333023 Change-Id: I32d46f93a99d4ec34c741f3c52b0646d141614f9 Reviewed-on: http://review.gluster.org/14214 Tested-by: Prashanth Pai <ppai@redhat.com> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org> CentOS-regression: Gluster Build System <jenkins@build.gluster.com> Tested-by: Gluster Build System <jenkins@build.gluster.com> Smoke: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Raghavendra G <rgowdapp@redhat.com> Tested-by: Raghavendra G <rgowdapp@redhat.com>
Diffstat (limited to 'libglusterfs/src/glusterfs.h')
-rw-r--r--libglusterfs/src/glusterfs.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/libglusterfs/src/glusterfs.h b/libglusterfs/src/glusterfs.h
index 2efa3a8f470..28d894fb8e1 100644
--- a/libglusterfs/src/glusterfs.h
+++ b/libglusterfs/src/glusterfs.h
@@ -89,6 +89,7 @@
#define GF_INTERNAL_IGNORE_DEEM_STATFS "ignore-deem-statfs"
#define GF_READDIR_SKIP_DIRS "readdir-filter-directories"
+#define GF_MDC_LOADED_KEY_NAMES "glusterfs.mdc.loaded.key.names"
#define BD_XATTR_KEY "user.glusterfs"
#define GF_PREOP_PARENT_KEY "glusterfs.preop.parent.key"