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ceph: document unlocked d_parent accesses

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For the most part we don't care about racing with rename when directing
MDS requests; either the old or new parent is fine.  Document that, and
do some minor cleanup.

Reviewed-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2011-07-26 11:31:26 -07:00
parent 41b02e1f9b
commit d79698da32
2 changed files with 11 additions and 4 deletions
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2
fs/ceph/dir.c
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@ -506,7 +506,7 @@ int ceph_handle_snapdir(struct ceph_mds_request *req,
struct dentry *dentry, int err)
{
struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
struct inode *parent = dentry->d_parent->d_inode;
struct inode *parent = dentry->d_parent->d_inode; /* we hold i_mutex */
/* .snap dir? */
if (err == -ENOENT &&

13
fs/ceph/mds_client.c
View File

@ -621,6 +621,12 @@ static void __unregister_request(struct ceph_mds_client *mdsc,
*/
struct dentry *get_nonsnap_parent(struct dentry *dentry)
{
/*
* we don't need to worry about protecting the d_parent access
* here because we never renaming inside the snapped namespace
* except to resplice to another snapdir, and either the old or new
* result is a valid result.
*/
while (!IS_ROOT(dentry) && ceph_snap(dentry->d_inode) != CEPH_NOSNAP)
dentry = dentry->d_parent;
return dentry;
@ -656,7 +662,9 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
if (req->r_inode) {
inode = req->r_inode;
} else if (req->r_dentry) {
struct inode *dir = req->r_dentry->d_parent->d_inode;
/* ignore race with rename; old or new d_parent is okay */
struct dentry *parent = req->r_dentry->d_parent;
struct inode *dir = parent->d_inode;
if (dir->i_sb != mdsc->fsc->sb) {
/* not this fs! */
@ -664,8 +672,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
} else if (ceph_snap(dir) != CEPH_NOSNAP) {
/* direct snapped/virtual snapdir requests
* based on parent dir inode */
struct dentry *dn =
get_nonsnap_parent(req->r_dentry->d_parent);
struct dentry *dn = get_nonsnap_parent(parent);
inode = dn->d_inode;
dout("__choose_mds using nonsnap parent %p\n", inode);
} else if (req->r_dentry->d_inode) {