cifs: convert oplock breaks to use slow_work facility (try #4)

This is the fourth respin of the patch to convert oplock breaks to
use the slow_work facility.

A customer of ours was testing a backport of one of the earlier
patchsets, and hit a "Busy inodes after umount..." problem. An oplock
break job had raced with a umount, and the superblock got torn down and
its memory reused. When the oplock break job tried to dereference the
inode->i_sb, the kernel oopsed.

This patchset has the oplock break job hold an inode and vfsmount
reference until the oplock break completes.  With this, there should be
no need to take a tcon reference (the vfsmount implicitly holds one
already).

Currently, when an oplock break comes in there's a chance that the
oplock break job won't occur if the allocation of the oplock_q_entry
fails. There are also some rather nasty races in the allocation and
handling these structs.

Rather than allocating oplock queue entries when an oplock break comes
in, add a few extra fields to the cifsFileInfo struct. Get rid of the
dedicated cifs_oplock_thread as well and queue the oplock break job to
the slow_work thread pool.

This approach also has the advantage that the oplock break jobs can
potentially run in parallel rather than be serialized like they are
today.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 301e307e1279..941441d3e386 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -94,6 +94,7 @@ static void mark_open_files_invalid(struct cifsTconInfo *pTcon)
         list_for_each_safe(tmp, tmp1, &pTcon->openFileList) {
                 open_file = list_entry(tmp, struct cifsFileInfo, tlist);
                 open_file->invalidHandle = true;
+                open_file->oplock_break_cancelled = true;
         }
         write_unlock(&GlobalSMBSeslock);
         /* BB Add call to invalidate_inodes(sb) for all superblocks mounted