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

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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>
This commit is contained in:
Jeff Layton
2009-09-21 06:47:50 -04:00
committed by Steve French
parent 48541bd3dd
commit 3bc303c254
10 changed files with 119 additions and 175 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
fs/cifs/misc.c
View File

@@ -32,7 +32,6 @@
extern mempool_t *cifs_sm_req_poolp;
extern mempool_t *cifs_req_poolp;
extern struct task_struct *oplockThread;
/* The xid serves as a useful identifier for each incoming vfs request,
in a similar way to the mid which is useful to track each sent smb,
@@ -500,6 +499,7 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
struct cifsTconInfo *tcon;
struct cifsInodeInfo *pCifsInode;
struct cifsFileInfo *netfile;
int rc;
cFYI(1, ("Checking for oplock break or dnotify response"));
if ((pSMB->hdr.Command == SMB_COM_NT_TRANSACT) &&
@@ -569,19 +569,30 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
if (pSMB->Fid != netfile->netfid)
continue;
read_unlock(&GlobalSMBSeslock);
read_unlock(&cifs_tcp_ses_lock);
/*
* don't do anything if file is about to be
* closed anyway.
*/
if (netfile->closePend) {
read_unlock(&GlobalSMBSeslock);
read_unlock(&cifs_tcp_ses_lock);
return true;
}
cFYI(1, ("file id match, oplock break"));
pCifsInode = CIFS_I(netfile->pInode);
pCifsInode->clientCanCacheAll = false;
if (pSMB->OplockLevel == 0)
pCifsInode->clientCanCacheRead = false;
AllocOplockQEntry(netfile->pInode,
netfile->netfid, tcon);
cFYI(1, ("about to wake up oplock thread"));
if (oplockThread)
wake_up_process(oplockThread);
rc = slow_work_enqueue(&netfile->oplock_break);
if (rc) {
cERROR(1, ("failed to enqueue oplock "
"break: %d\n", rc));
} else {
netfile->oplock_break_cancelled = false;
}
read_unlock(&GlobalSMBSeslock);
read_unlock(&cifs_tcp_ses_lock);
return true;
}
read_unlock(&GlobalSMBSeslock);