cifs: don't fail writepages on -EAGAIN errors

If CIFSSMBWrite2 returns -EAGAIN, then the error should be considered
temporary. CIFS should retry the write instead of setting an error on
the mapping and returning.

For WB_SYNC_ALL, just retry the write immediately. In the WB_SYNC_NONE
case, call redirty_page_for_writeback on all of the pages that didn't
get written out and then move on.

Also, fix up the handling of a short write with a successful return
code. MS-CIFS says that 0 bytes_written means ENOSPC or EFBIG. It
doesn't mention what a short, but non-zero write means, so for now
treat it as we would an -EAGAIN return.

Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index af371910f543906eb59f0c1efdb7f5436e40ffd6..cfa2e5ebcafe87a1498894055340d8b6e7a3bd0c 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1377,6 +1377,7 @@ retry:
                                break;
                }
                if (n_iov) {
+retry_write:
                        open_file = find_writable_file(CIFS_I(mapping->host),
                                                        false);
                        if (!open_file) {
@@ -1389,31 +1390,55 @@ retry:
                                                   &bytes_written, iov, n_iov,
                                                   long_op);
                                cifsFileInfo_put(open_file);
-                               cifs_update_eof(cifsi, offset, bytes_written);
                        }
 
-                       if (rc || bytes_written < bytes_to_write) {
-                               cERROR(1, "Write2 ret %d, wrote %d",
-                                         rc, bytes_written);
-                               mapping_set_error(mapping, rc);
-                       } else {
+                       cFYI(1, "Write2 rc=%d, wrote=%u", rc, bytes_written);
+
+                       /*
+                        * For now, treat a short write as if nothing got
+                        * written. A zero length write however indicates
+                        * ENOSPC or EFBIG. We have no way to know which
+                        * though, so call it ENOSPC for now. EFBIG would
+                        * get translated to AS_EIO anyway.
+                        *
+                        * FIXME: make it take into account the data that did
+                        *        get written
+                        */
+                       if (rc == 0) {
+                               if (bytes_written == 0)
+                                       rc = -ENOSPC;
+                               else if (bytes_written < bytes_to_write)
+                                       rc = -EAGAIN;
+                       }
+
+                       /* retry on data-integrity flush */
+                       if (wbc->sync_mode == WB_SYNC_ALL && rc == -EAGAIN)
+                               goto retry_write;
+
+                       /* fix the stats and EOF */
+                       if (bytes_written > 0) {
                                cifs_stats_bytes_written(tcon, bytes_written);
+                               cifs_update_eof(cifsi, offset, bytes_written);
                        }
 
                        for (i = 0; i < n_iov; i++) {
                                page = pvec.pages[first + i];
-                               /* Should we also set page error on
-                               success rc but too little data written? */
-                               /* BB investigate retry logic on temporary
-                               server crash cases and how recovery works
-                               when page marked as error */
-                               if (rc)
+                               /* on retryable write error, redirty page */
+                               if (rc == -EAGAIN)
+                                       redirty_page_for_writepage(wbc, page);
+                               else if (rc != 0)
                                        SetPageError(page);
                                kunmap(page);
                                unlock_page(page);
                                end_page_writeback(page);
                                page_cache_release(page);
                        }
+
+                       if (rc != -EAGAIN)
+                               mapping_set_error(mapping, rc);
+                       else
+                               rc = 0;
+
                        if ((wbc->nr_to_write -= n_iov) <= 0)
                                done = 1;
                        index = next;