[CIFS] Fix hang in find_writable_file

Caused by unneeded reopen during reconnect while spinlock held.

Fixes kernel bugzilla bug #7903

Thanks to Lin Feng Shen for testing this, and Amit Arora for
some nice problem determination to narrow this down.

Acked-by: Dave Kleikamp <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 23 insertions, 10 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e13592afca9..894b1f7b299 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1904,6 +1904,25 @@ static int cifs_readpage(struct file *file, struct page *page)
         return rc;
 }
 
+static int is_inode_writable(struct cifsInodeInfo *cifs_inode)
+{
+        struct cifsFileInfo *open_file;
+
+        read_lock(&GlobalSMBSeslock);
+        list_for_each_entry(open_file, &cifs_inode->openFileList, flist) {
+                if (open_file->closePend)
+                        continue;
+                if (open_file->pfile &&
+                    ((open_file->pfile->f_flags & O_RDWR) ||
+                     (open_file->pfile->f_flags & O_WRONLY))) {
+                        read_unlock(&GlobalSMBSeslock);
+                        return 1;
+                }
+        }
+        read_unlock(&GlobalSMBSeslock);
+        return 0;
+}
+
 /* We do not want to update the file size from server for inodes
    open for write - to avoid races with writepage extending
    the file - in the future we could consider allowing
@@ -1912,19 +1931,13 @@ static int cifs_readpage(struct file *file, struct page *page)
    page caching in the current Linux kernel design */
 int is_size_safe_to_change(struct cifsInodeInfo *cifsInode, __u64 end_of_file)
 {
-        struct cifsFileInfo *open_file = NULL;
-
-        if (cifsInode)
-                open_file =  find_writable_file(cifsInode);
+        if (!cifsInode)
+                return 1;
 
-        if (open_file) {
+        if (is_inode_writable(cifsInode)) {
+                /* This inode is open for write at least once */
                 struct cifs_sb_info *cifs_sb;
 
-                /* there is not actually a write pending so let
-                this handle go free and allow it to
-                be closable if needed */
-                atomic_dec(&open_file->wrtPending);
-
                 cifs_sb = CIFS_SB(cifsInode->vfs_inode.i_sb);
                 if ( cifs_sb->mnt_cifs_flags & CIFS_MOUNT_DIRECT_IO ) {
                         /* since no page cache to corrupt on directio