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authorMiklos Szeredi <mszeredi@suse.cz>2012-05-21 17:30:19 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2012-06-01 12:12:01 -0400
commit16b1c1cd71176ab0a76b26818fbf12db9183ed57 (patch)
treeda4ab8077cc3d9dce5b6ec2d003074cba3841446
parent50ee93afcaa970620d1fb5a9894109a2ab152868 (diff)
vfs: retry last component if opening stale dentry
NFS optimizes away d_revalidates for last component of open. This means that open itself can find the dentry stale. This patch allows the filesystem to return EOPENSTALE and the VFS will retry the lookup on just the last component if possible. If the lookup was done using RCU mode, including the last component, then this is not possible since the parent dentry is lost. In this case fall back to non-RCU lookup. Currently this is not used since NFS will always leave RCU mode. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/namei.c37
-rw-r--r--include/linux/errno.h1
2 files changed, 36 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 998d5316921..7d694194024 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2202,6 +2202,8 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
struct file *filp;
struct inode *inode;
int symlink_ok = 0;
+ struct path save_parent = { .dentry = NULL, .mnt = NULL };
+ bool retried = false;
int error;
nd->flags &= ~LOOKUP_PARENT;
@@ -2267,6 +2269,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
if (nd->last.name[nd->last.len])
goto exit;
+retry_lookup:
mutex_lock(&dir->d_inode->i_mutex);
dentry = lookup_hash(nd);
@@ -2349,12 +2352,21 @@ finish_lookup:
return NULL;
}
- path_to_nameidata(path, nd);
+ if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
+ path_to_nameidata(path, nd);
+ } else {
+ save_parent.dentry = nd->path.dentry;
+ save_parent.mnt = mntget(path->mnt);
+ nd->path.dentry = path->dentry;
+
+ }
nd->inode = inode;
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
error = complete_walk(nd);
- if (error)
+ if (error) {
+ path_put(&save_parent);
return ERR_PTR(error);
+ }
error = -EISDIR;
if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
goto exit;
@@ -2377,6 +2389,20 @@ common:
if (error)
goto exit;
filp = nameidata_to_filp(nd);
+ if (filp == ERR_PTR(-EOPENSTALE) && save_parent.dentry && !retried) {
+ BUG_ON(save_parent.dentry != dir);
+ path_put(&nd->path);
+ nd->path = save_parent;
+ nd->inode = dir->d_inode;
+ save_parent.mnt = NULL;
+ save_parent.dentry = NULL;
+ if (want_write) {
+ mnt_drop_write(nd->path.mnt);
+ want_write = 0;
+ }
+ retried = true;
+ goto retry_lookup;
+ }
if (!IS_ERR(filp)) {
error = ima_file_check(filp, op->acc_mode);
if (error) {
@@ -2396,6 +2422,7 @@ common:
out:
if (want_write)
mnt_drop_write(nd->path.mnt);
+ path_put(&save_parent);
terminate_walk(nd);
return filp;
@@ -2459,6 +2486,12 @@ out:
if (base)
fput(base);
release_open_intent(nd);
+ if (filp == ERR_PTR(-EOPENSTALE)) {
+ if (flags & LOOKUP_RCU)
+ filp = ERR_PTR(-ECHILD);
+ else
+ filp = ERR_PTR(-ESTALE);
+ }
return filp;
out_filp:
diff --git a/include/linux/errno.h b/include/linux/errno.h
index 2d09bfa5c26..e0de516374d 100644
--- a/include/linux/errno.h
+++ b/include/linux/errno.h
@@ -17,6 +17,7 @@
#define ENOIOCTLCMD 515 /* No ioctl command */
#define ERESTART_RESTARTBLOCK 516 /* restart by calling sys_restart_syscall */
#define EPROBE_DEFER 517 /* Driver requests probe retry */
+#define EOPENSTALE 518 /* open found a stale dentry */
/* Defined for the NFSv3 protocol */
#define EBADHANDLE 521 /* Illegal NFS file handle */