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Subject[PATCH 4/7] cifs: use workqueue instead of slow-work
Date
Workqueue can now handle high concurrency.  Use system_nrt_wq
instead of slow-work.

* Updated is_valid_oplock_break() to not call cifs_oplock_break_put()
as advised by Steve French. It might cause deadlock. Instead,
reference is increased after queueing succeeded and
cifs_oplock_break() briefly grabs GlobalSMBSeslock before putting
the cfile to make sure it doesn't put before the matching get is
finished.

* Anton Blanchard reported that cifs conversion was using now gone
system_single_wq. Use system_nrt_wq which provides non-reentrance
guarantee which is enough and much better.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Steve French <sfrench@samba.org>
Cc: Anton Blanchard <anton@samba.org>
---
fs/cifs/Kconfig | 1 -
fs/cifs/cifsfs.c | 5 -----
fs/cifs/cifsglob.h | 8 +++++---
fs/cifs/dir.c | 2 +-
fs/cifs/file.c | 30 +++++++++++++-----------------
fs/cifs/misc.c | 20 ++++++++++++--------
6 files changed, 31 insertions(+), 35 deletions(-)
diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 80f3525..6994a0f 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -2,7 +2,6 @@ config CIFS
tristate "CIFS support (advanced network filesystem, SMBFS successor)"
depends on INET
select NLS
- select SLOW_WORK
help
This is the client VFS module for the Common Internet File System
(CIFS) protocol which is the successor to the Server Message Block
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 78c02eb..4c07517 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -917,15 +917,10 @@ init_cifs(void)
if (rc)
goto out_unregister_key_type;
#endif
- rc = slow_work_register_user(THIS_MODULE);
- if (rc)
- goto out_unregister_resolver_key;

return 0;

- out_unregister_resolver_key:
#ifdef CONFIG_CIFS_DFS_UPCALL
- unregister_key_type(&key_type_dns_resolver);
out_unregister_key_type:
#endif
#ifdef CONFIG_CIFS_UPCALL
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index a88479c..f5a1f9b 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -19,7 +19,7 @@
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/slab.h>
-#include <linux/slow-work.h>
+#include <linux/workqueue.h>
#include "cifs_fs_sb.h"
#include "cifsacl.h"
/*
@@ -363,7 +363,7 @@ struct cifsFileInfo {
atomic_t count; /* reference count */
struct mutex fh_mutex; /* prevents reopen race after dead ses*/
struct cifs_search_info srch_inf;
- struct slow_work oplock_break; /* slow_work job for oplock breaks */
+ struct work_struct oplock_break; /* work for oplock breaks */
};

/* Take a reference on the file private data */
@@ -732,4 +732,6 @@ GLOBAL_EXTERN unsigned int cifs_min_rcv; /* min size of big ntwrk buf pool */
GLOBAL_EXTERN unsigned int cifs_min_small; /* min size of small buf pool */
GLOBAL_EXTERN unsigned int cifs_max_pending; /* MAX requests at once to server*/

-extern const struct slow_work_ops cifs_oplock_break_ops;
+void cifs_oplock_break(struct work_struct *work);
+void cifs_oplock_break_get(struct cifsFileInfo *cfile);
+void cifs_oplock_break_put(struct cifsFileInfo *cfile);
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 391816b..b066e73 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -162,7 +162,7 @@ cifs_new_fileinfo(struct inode *newinode, __u16 fileHandle,
mutex_init(&pCifsFile->lock_mutex);
INIT_LIST_HEAD(&pCifsFile->llist);
atomic_set(&pCifsFile->count, 1);
- slow_work_init(&pCifsFile->oplock_break, &cifs_oplock_break_ops);
+ INIT_WORK(&pCifsFile->oplock_break, cifs_oplock_break);

write_lock(&GlobalSMBSeslock);
list_add(&pCifsFile->tlist, &cifs_sb->tcon->openFileList);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 75541af..e767bfa 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2295,8 +2295,7 @@ out:
return rc;
}

-static void
-cifs_oplock_break(struct slow_work *work)
+void cifs_oplock_break(struct work_struct *work)
{
struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
oplock_break);
@@ -2333,33 +2332,30 @@ cifs_oplock_break(struct slow_work *work)
LOCKING_ANDX_OPLOCK_RELEASE, false);
cFYI(1, "Oplock release rc = %d", rc);
}
+
+ /*
+ * We might have kicked in before is_valid_oplock_break()
+ * finished grabbing reference for us. Make sure it's done by
+ * waiting for GlobalSMSSeslock.
+ */
+ write_lock(&GlobalSMBSeslock);
+ write_unlock(&GlobalSMBSeslock);
+
+ cifs_oplock_break_put(cfile);
}

-static int
-cifs_oplock_break_get(struct slow_work *work)
+void cifs_oplock_break_get(struct cifsFileInfo *cfile)
{
- struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
- oplock_break);
mntget(cfile->mnt);
cifsFileInfo_get(cfile);
- return 0;
}

-static void
-cifs_oplock_break_put(struct slow_work *work)
+void cifs_oplock_break_put(struct cifsFileInfo *cfile)
{
- struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
- oplock_break);
mntput(cfile->mnt);
cifsFileInfo_put(cfile);
}

-const struct slow_work_ops cifs_oplock_break_ops = {
- .get_ref = cifs_oplock_break_get,
- .put_ref = cifs_oplock_break_put,
- .execute = cifs_oplock_break,
-};
-
const struct address_space_operations cifs_addr_ops = {
.readpage = cifs_readpage,
.readpages = cifs_readpages,
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 1394aa3..3ccadc1 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -498,7 +498,6 @@ 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) &&
@@ -583,13 +582,18 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
pCifsInode->clientCanCacheAll = false;
if (pSMB->OplockLevel == 0)
pCifsInode->clientCanCacheRead = false;
- 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;
- }
+
+ /*
+ * cifs_oplock_break_put() can't be called
+ * from here. Get reference after queueing
+ * succeeded. cifs_oplock_break() will
+ * synchronize using GlobalSMSSeslock.
+ */
+ if (queue_work(system_nrt_wq,
+ &netfile->oplock_break))
+ cifs_oplock_break_get(netfile);
+ netfile->oplock_break_cancelled = false;
+
read_unlock(&GlobalSMBSeslock);
read_unlock(&cifs_tcp_ses_lock);
return true;
--
1.6.4.2


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