xfs: don't block on buffer read errors

xfs_buf_read() fails to detect dispatch errors before attempting to
wait on sychronous IO. If there was an error, it will get stuck
forever, waiting for an I/O that was never started. Make sure the
error is detected correctly.

Further, such a failure can leave locked pages in the page cache
which will cause a later operation to hang on the page. Ensure that
we correctly process pages in the buffers when we get a dispatch
error.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 15 insertions, 4 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index efce8abb375c..f4d4e708a8d6 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -578,9 +578,9 @@ _xfs_buf_read(
                         XBF_READ_AHEAD | _XBF_RUN_QUEUES);
 
         status = xfs_buf_iorequest(bp);
-        if (!status && !(flags & XBF_ASYNC))
-                status = xfs_buf_iowait(bp);
-        return status;
+        if (status || XFS_BUF_ISERROR(bp) || (flags & XBF_ASYNC))
+                return status;
+        return xfs_buf_iowait(bp);
 }
 
 xfs_buf_t *
@@ -1280,8 +1280,19 @@ submit_io:
                 if (size)
                         goto next_chunk;
         } else {
-                bio_put(bio);
+                /*
+                 * if we get here, no pages were added to the bio. However,
+                 * we can't just error out here - if the pages are locked then
+                 * we have to unlock them otherwise we can hang on a later
+                 * access to the page.
+                 */
                 xfs_buf_ioerror(bp, EIO);
+                if (bp->b_flags & _XBF_PAGE_LOCKED) {
+                        int i;
+                        for (i = 0; i < bp->b_page_count; i++)
+                                unlock_page(bp->b_pages[i]);
+                }
+                bio_put(bio);
         }
 }