cifs: report error instead of invalid when revalidating a dentry fails

BugLink: https://bugs.launchpad.net/bugs/1916066
commit 21b200d091826a83aafc95d847139b2b0582f6d1 upstream.

Assuming
- //HOST/a is mounted on /mnt
- //HOST/b is mounted on /mnt/b

On a slow connection, running 'df' and killing it while it's
processing /mnt/b can make cifs_get_inode_info() returns -ERESTARTSYS.

This triggers the following chain of events:
=> the dentry revalidation fail
=> dentry is put and released
=> superblock associated with the dentry is put
=> /mnt/b is unmounted

This patch makes cifs_d_revalidate() return the error instead of 0
(invalid) when cifs_revalidate_dentry() fails, except for ENOENT (file
deleted) and ESTALE (file recreated).

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Suggested-by: Shyam Prasad N <nspmangalore@gmail.com>
Reviewed-by: Shyam Prasad N <nspmangalore@gmail.com>
CC: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 5a35850ccb1abe953f35396821f187269de928fd..9ae9a514676c3ea8bcf52e981de46e17d9d4c25d 100644 (file)
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -738,6 +738,7 @@ static int
 cifs_d_revalidate(struct dentry *direntry, unsigned int flags)
 {
        struct inode *inode;
+       int rc;
 
        if (flags & LOOKUP_RCU)
                return -ECHILD;
@@ -747,8 +748,25 @@ cifs_d_revalidate(struct dentry *direntry, unsigned int flags)
                if ((flags & LOOKUP_REVAL) && !CIFS_CACHE_READ(CIFS_I(inode)))
                        CIFS_I(inode)->time = 0; /* force reval */
 
-               if (cifs_revalidate_dentry(direntry))
-                       return 0;
+               rc = cifs_revalidate_dentry(direntry);
+               if (rc) {
+                       cifs_dbg(FYI, "cifs_revalidate_dentry failed with rc=%d", rc);
+                       switch (rc) {
+                       case -ENOENT:
+                       case -ESTALE:
+                               /*
+                                * Those errors mean the dentry is invalid
+                                * (file was deleted or recreated)
+                                */
+                               return 0;
+                       default:
+                               /*
+                                * Otherwise some unexpected error happened
+                                * report it as-is to VFS layer
+                                */
+                               return rc;
+                       }
+               }
                else {
                        /*
                         * If the inode wasn't known to be a dfs entry when