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authorSage Weil <sage@newdream.net>2011-07-26 18:30:15 (GMT)
committerSage Weil <sage@newdream.net>2011-07-26 18:30:15 (GMT)
commit48d0cbd1242aac969560ef8b90f26ee3b09a6a5c (patch)
tree228a26f8ee7d555d67c6a00e5346f3b558a2e48c
parentdfabbed6fdd509dc2beb89c954bc36014a1bc7cb (diff)
ceph: handle racing calls to ceph_init_dentry
The ->lookup() and prepopulate_readdir() callers are working with unhashed dentries, so we don't have to worry. The export.c callers, though, need to initialize something they got back from d_obtain_alias() and are potentially racing with other callers. Make sure we don't return unless the dentry is properly initialized (by us or someone else). Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Reviewed-by: Yehuda Sadeh <yehuda@hq.newdream.net> Signed-off-by: Sage Weil <sage@newdream.net>
-rw-r--r--fs/ceph/dir.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index f39a409..883c954 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -40,14 +40,6 @@ int ceph_init_dentry(struct dentry *dentry)
if (dentry->d_fsdata)
return 0;
- if (dentry->d_parent == NULL || /* nfs fh_to_dentry */
- ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
- d_set_d_op(dentry, &ceph_dentry_ops);
- else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)
- d_set_d_op(dentry, &ceph_snapdir_dentry_ops);
- else
- d_set_d_op(dentry, &ceph_snap_dentry_ops);
-
di = kmem_cache_alloc(ceph_dentry_cachep, GFP_NOFS | __GFP_ZERO);
if (!di)
return -ENOMEM; /* oh well */
@@ -58,10 +50,21 @@ int ceph_init_dentry(struct dentry *dentry)
kmem_cache_free(ceph_dentry_cachep, di);
goto out_unlock;
}
+
+ if (dentry->d_parent == NULL || /* nfs fh_to_dentry */
+ ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
+ d_set_d_op(dentry, &ceph_dentry_ops);
+ else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)
+ d_set_d_op(dentry, &ceph_snapdir_dentry_ops);
+ else
+ d_set_d_op(dentry, &ceph_snap_dentry_ops);
+
di->dentry = dentry;
di->lease_session = NULL;
- dentry->d_fsdata = di;
dentry->d_time = jiffies;
+ /* avoid reordering d_fsdata setup so that the check above is safe */
+ smp_mb();
+ dentry->d_fsdata = di;
ceph_dentry_lru_add(dentry);
out_unlock:
spin_unlock(&dentry->d_lock);

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