fs/9p: Prevent parallel rename when doing fid_lookup
During fid lookup we need to make sure that the dentry->d_parent doesn't
change so that we can safely walk the parent dentries. To ensure that
we need to prevent cross directory rename during fid_lookup. Add a
per superblock rename_sem rw_semaphore to prevent parallel fid lookup and
rename.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index 5d6cfcb..3585636 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -97,6 +97,34 @@
return ret;
}
+/*
+ * We need to hold v9ses->rename_sem as long as we hold references
+ * to returned path array. Array element contain pointers to
+ * dentry names.
+ */
+static int build_path_from_dentry(struct v9fs_session_info *v9ses,
+ struct dentry *dentry, char ***names)
+{
+ int n = 0, i;
+ char **wnames;
+ struct dentry *ds;
+
+ for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
+ n++;
+
+ wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
+ if (!wnames)
+ goto err_out;
+
+ for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
+ wnames[i] = (char *)ds->d_name.name;
+
+ *names = wnames;
+ return n;
+err_out:
+ return -ENOMEM;
+}
+
/**
* v9fs_fid_lookup - lookup for a fid, try to walk if not found
* @dentry: dentry to look for fid in
@@ -112,7 +140,7 @@
int i, n, l, clone, any, access;
u32 uid;
struct p9_fid *fid, *old_fid = NULL;
- struct dentry *d, *ds;
+ struct dentry *ds;
struct v9fs_session_info *v9ses;
char **wnames, *uname;
@@ -139,50 +167,62 @@
fid = v9fs_fid_find(dentry, uid, any);
if (fid)
return fid;
-
+ /*
+ * we don't have a matching fid. To do a TWALK we need
+ * parent fid. We need to prevent rename when we want to
+ * look at the parent.
+ */
+ down_read(&v9ses->rename_sem);
ds = dentry->d_parent;
fid = v9fs_fid_find(ds, uid, any);
- if (!fid) { /* walk from the root */
- n = 0;
- for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
- n++;
+ if (fid) {
+ /* Found the parent fid do a lookup with that */
+ fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);
+ goto fid_out;
+ }
+ up_read(&v9ses->rename_sem);
- fid = v9fs_fid_find(ds, uid, any);
- if (!fid) { /* the user is not attached to the fs yet */
- if (access == V9FS_ACCESS_SINGLE)
- return ERR_PTR(-EPERM);
+ /* start from the root and try to do a lookup */
+ fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
+ if (!fid) {
+ /* the user is not attached to the fs yet */
+ if (access == V9FS_ACCESS_SINGLE)
+ return ERR_PTR(-EPERM);
- if (v9fs_proto_dotu(v9ses) ||
- v9fs_proto_dotl(v9ses))
+ if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
uname = NULL;
- else
- uname = v9ses->uname;
+ else
+ uname = v9ses->uname;
- fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
- v9ses->aname);
+ fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
+ v9ses->aname);
+ if (IS_ERR(fid))
+ return fid;
- if (IS_ERR(fid))
- return fid;
-
- v9fs_fid_add(ds, fid);
- }
- } else /* walk from the parent */
- n = 1;
-
- if (ds == dentry)
+ v9fs_fid_add(dentry->d_sb->s_root, fid);
+ }
+ /* If we are root ourself just return that */
+ if (dentry->d_sb->s_root == dentry)
return fid;
-
- wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
- if (!wnames)
- return ERR_PTR(-ENOMEM);
-
- for (d = dentry, i = (n-1); i >= 0; i--, d = d->d_parent)
- wnames[i] = (char *) d->d_name.name;
-
+ /*
+ * Do a multipath walk with attached root.
+ * When walking parent we need to make sure we
+ * don't have a parallel rename happening
+ */
+ down_read(&v9ses->rename_sem);
+ n = build_path_from_dentry(v9ses, dentry, &wnames);
+ if (n < 0) {
+ fid = ERR_PTR(n);
+ goto err_out;
+ }
clone = 1;
i = 0;
while (i < n) {
l = min(n - i, P9_MAXWELEM);
+ /*
+ * We need to hold rename lock when doing a multipath
+ * walk to ensure none of the patch component change
+ */
fid = p9_client_walk(fid, l, &wnames[i], clone);
if (IS_ERR(fid)) {
if (old_fid) {
@@ -194,15 +234,17 @@
p9_client_clunk(old_fid);
}
kfree(wnames);
- return fid;
+ goto err_out;
}
old_fid = fid;
i += l;
clone = 0;
}
-
kfree(wnames);
+fid_out:
v9fs_fid_add(dentry, fid);
+err_out:
+ up_read(&v9ses->rename_sem);
return fid;
}
diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index 3c49201..38dc0e0 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -237,6 +237,7 @@
__putname(v9ses->uname);
return ERR_PTR(-ENOMEM);
}
+ init_rwsem(&v9ses->rename_sem);
rc = bdi_setup_and_register(&v9ses->bdi, "9p", BDI_CAP_MAP_COPY);
if (rc) {
diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index bec4d0b..4c963c9 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -104,6 +104,7 @@
struct p9_client *clnt; /* 9p client */
struct list_head slist; /* list of sessions registered with v9fs */
struct backing_dev_info bdi;
+ struct rw_semaphore rename_sem;
};
struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *,
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 39352ef..75c261f 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -948,6 +948,7 @@
sb = dir->i_sb;
v9ses = v9fs_inode2v9ses(dir);
+ /* We can walk d_parent because we hold the dir->i_mutex */
dfid = v9fs_fid_lookup(dentry->d_parent);
if (IS_ERR(dfid))
return ERR_CAST(dfid);
@@ -1055,27 +1056,33 @@
goto clunk_olddir;
}
+ down_write(&v9ses->rename_sem);
if (v9fs_proto_dotl(v9ses)) {
retval = p9_client_rename(oldfid, newdirfid,
(char *) new_dentry->d_name.name);
if (retval != -ENOSYS)
goto clunk_newdir;
}
+ if (old_dentry->d_parent != new_dentry->d_parent) {
+ /*
+ * 9P .u can only handle file rename in the same directory
+ */
- /* 9P can only handle file rename in the same directory */
- if (memcmp(&olddirfid->qid, &newdirfid->qid, sizeof(newdirfid->qid))) {
P9_DPRINTK(P9_DEBUG_ERROR,
"old dir and new dir are different\n");
retval = -EXDEV;
goto clunk_newdir;
}
-
v9fs_blank_wstat(&wstat);
wstat.muid = v9ses->uname;
wstat.name = (char *) new_dentry->d_name.name;
retval = p9_client_wstat(oldfid, &wstat);
clunk_newdir:
+ if (!retval)
+ /* successful rename */
+ d_move(old_dentry, new_dentry);
+ up_write(&v9ses->rename_sem);
p9_client_clunk(newdirfid);
clunk_olddir:
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 0a2e203..4b9ede0 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -287,4 +287,5 @@
.get_sb = v9fs_get_sb,
.kill_sb = v9fs_kill_super,
.owner = THIS_MODULE,
+ .fs_flags = FS_RENAME_DOES_D_MOVE,
};
