NFS: Fix a hang/infinite loop in nfs_wb_page()

When one of the two waits in nfs_commit_inode() is interrupted, it
returns a non-negative value, which causes nfs_wb_page() to think
that the operation was successful causing it to busy-loop rather
than exiting.
It also causes nfs_file_fsync() to incorrectly report the file as
being successfully committed to disk.

This patch fixes both problems by ensuring that we return an error
if the attempts to wait fail.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

1 files changed, 19 insertions, 12 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 4d686ee53244..55a8c3671233 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1261,13 +1261,17 @@ void nfs_writeback_done(struct rpc_task *task, struct nfs_write_data *data)
 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
 static int nfs_commit_set_lock(struct nfs_inode *nfsi, int may_wait)
 {
+        int ret;
+
         if (!test_and_set_bit(NFS_INO_COMMIT, &nfsi->flags))
                 return 1;
-        if (may_wait && !out_of_line_wait_on_bit_lock(&nfsi->flags,
-                                NFS_INO_COMMIT, nfs_wait_bit_killable,
-                                TASK_KILLABLE))
-                return 1;
-        return 0;
+        if (!may_wait)
+                return 0;
+        ret = out_of_line_wait_on_bit_lock(&nfsi->flags,
+                                NFS_INO_COMMIT,
+                                nfs_wait_bit_killable,
+                                TASK_KILLABLE);
+        return (ret < 0) ? ret : 1;
 }
 
 static void nfs_commit_clear_lock(struct nfs_inode *nfsi)
@@ -1443,9 +1447,10 @@ int nfs_commit_inode(struct inode *inode, int how)
 {
         LIST_HEAD(head);
         int may_wait = how & FLUSH_SYNC;
-        int res = 0;
+        int res;
 
-        if (!nfs_commit_set_lock(NFS_I(inode), may_wait))
+        res = nfs_commit_set_lock(NFS_I(inode), may_wait);
+        if (res <= 0)
                 goto out_mark_dirty;
         spin_lock(&inode->i_lock);
         res = nfs_scan_commit(inode, &head, 0, 0);
@@ -1454,12 +1459,14 @@ int nfs_commit_inode(struct inode *inode, int how)
                 int error = nfs_commit_list(inode, &head, how);
                 if (error < 0)
                         return error;
-                if (may_wait)
-                        wait_on_bit(&NFS_I(inode)->flags, NFS_INO_COMMIT,
-                                        nfs_wait_bit_killable,
-                                        TASK_KILLABLE);
-                else
+                if (!may_wait)
                         goto out_mark_dirty;
+                error = wait_on_bit(&NFS_I(inode)->flags,
+                                NFS_INO_COMMIT,
+                                nfs_wait_bit_killable,
+                                TASK_KILLABLE);
+                if (error < 0)
+                        return error;
         } else
                 nfs_commit_clear_lock(NFS_I(inode));
         return res;