From: Aurelien Aptel <redacted>

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 <redacted>
Suggested-by: Shyam Prasad N <redacted>
CC: stable@vger.kernel.org

---
 fs/cifs/dir.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 68900f1629bff..97ac363b5df16 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c

@@ -737,6 +737,7 @@ static int
 cifs_d_revalidate(struct dentry *direntry, unsigned int flags)
 {
        struct inode *inode;
+       int rc;

        if (flags & LOOKUP_RCU)
                return -ECHILD;

@@ -746,8 +747,25 @@ 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
--

2.29.2