Re: oops in deferred close

[Rohith Surabattula <rohiths.msft@gmail.com>]

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Hi All,

Have updated the commit message.
Please review and let me know if it is fine.

Regards,
Rohith

On Fri, May 14, 2021 at 3:49 PM Rohith Surabattula
<rohiths.msft@gmail.com> wrote:
>
> Hi Aurélien,
>
> Sorry for the late reply.I am on vacation this week.
>
> I have added the oplock_break_received flag as part of my first commit
> to achieve synchronization between oplock thread and open thread. But
> there is already a lock "open_file_lock" to achieve the same. So, I
> removed the same.
>
> find_readable_file takes open_file_lock and then traverse the
> openFileList. Similarly, cifs_oplock_break while closing the deferred
> handle(i.e cifsFileInfo_put) takes open_file_lock and then sends close
> to the server.
>
> Regards,
> Rohith
>
> On Tue, May 11, 2021 at 9:59 PM Aurélien Aptel <aaptel@suse.com> wrote:
> >
> > Hi,
> >
> > Rohith Surabattula <rohiths.msft@gmail.com> writes:
> > > Will fix the oops which caused the above issue.
> >
> > The patch Steve forwarded to me (I think you forgot to attach it) is not
> > so obvious to me. Could you explain more in the commit msg why you
> > removed oplock_break_received flag
> >
> > Cheers,
> > --
> > Aurélien Aptel / SUSE Labs Samba Team
> > GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
> > SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
> > GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)
> >

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From 0e0dd29ee9790fbc8e490f986640accedb259d43 Mon Sep 17 00:00:00 2001
From: Rohith Surabattula <rohiths@microsoft.com>
Date: Wed, 5 May 2021 10:56:47 +0000
Subject: [PATCH] Fix kernel oops when CONFIG_DEBUG_ATOMIC_SLEEP is
 enabled.

Removed oplock_break_received flag which was added to achive
synchronization between oplock handler and open handler by earlier commit.

It is not needed because there is an existing lock open_file_lock to achieve
the same.find_readable_file takes open_file_lock and then traverse the
openFileList. Similarly, cifs_oplock_break while closing the deferred
handle(i.e cifsFileInfo_put) takes open_file_lock and then sends close
to the server.

Added comments for better readability.

Signed-off-by: Rohith Surabattula <rohiths@microsoft.com>
---
 fs/cifs/cifsfs.c   |  2 +-
 fs/cifs/cifsglob.h |  3 +--
 fs/cifs/file.c     | 27 ++++++++++++---------------
 fs/cifs/misc.c     |  9 +++++++++
 4 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index d7ea9c5fe0f8..2ffcb29d5c8f 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -133,7 +133,7 @@ struct workqueue_struct	*cifsiod_wq;
 struct workqueue_struct	*decrypt_wq;
 struct workqueue_struct	*fileinfo_put_wq;
 struct workqueue_struct	*cifsoplockd_wq;
-struct workqueue_struct *deferredclose_wq;
+struct workqueue_struct	*deferredclose_wq;
 __u32 cifs_lock_secret;
 
 /*
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index d88b4b523dcc..ea90c53386b8 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1257,8 +1257,7 @@ struct cifsFileInfo {
 	struct work_struct oplock_break; /* work for oplock breaks */
 	struct work_struct put; /* work for the final part of _put */
 	struct delayed_work deferred;
-	bool oplock_break_received; /* Flag to indicate oplock break */
-	bool deferred_scheduled;
+	bool deferred_close_scheduled; /* Flag to indicate close is scheduled */
 };
 
 struct cifs_io_parms {
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 919c82d4713d..ccdf9b62062a 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -323,8 +323,7 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
 	cfile->dentry = dget(dentry);
 	cfile->f_flags = file->f_flags;
 	cfile->invalidHandle = false;
-	cfile->oplock_break_received = false;
-	cfile->deferred_scheduled = false;
+	cfile->deferred_close_scheduled = false;
 	cfile->tlink = cifs_get_tlink(tlink);
 	INIT_WORK(&cfile->oplock_break, cifs_oplock_break);
 	INIT_WORK(&cfile->put, cifsFileInfo_put_work);
@@ -574,21 +573,18 @@ int cifs_open(struct inode *inode, struct file *file)
 			file->f_op = &cifs_file_direct_ops;
 	}
 
-	spin_lock(&CIFS_I(inode)->deferred_lock);
 	/* Get the cached handle as SMB2 close is deferred */
 	rc = cifs_get_readable_path(tcon, full_path, &cfile);
 	if (rc == 0) {
 		if (file->f_flags == cfile->f_flags) {
 			file->private_data = cfile;
+			spin_lock(&CIFS_I(inode)->deferred_lock);
 			cifs_del_deferred_close(cfile);
 			spin_unlock(&CIFS_I(inode)->deferred_lock);
 			goto out;
 		} else {
-			spin_unlock(&CIFS_I(inode)->deferred_lock);
 			_cifsFileInfo_put(cfile, true, false);
 		}
-	} else {
-		spin_unlock(&CIFS_I(inode)->deferred_lock);
 	}
 
 	if (server->oplocks)
@@ -878,12 +874,12 @@ void smb2_deferred_work_close(struct work_struct *work)
 			struct cifsFileInfo, deferred.work);
 
 	spin_lock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
-	if (!cfile->deferred_scheduled) {
+	if (!cfile->deferred_close_scheduled) {
 		spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
 		return;
 	}
 	cifs_del_deferred_close(cfile);
-	cfile->deferred_scheduled = false;
+	cfile->deferred_close_scheduled = false;
 	spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
 	_cifsFileInfo_put(cfile, true, false);
 }
@@ -905,14 +901,15 @@ int cifs_close(struct inode *inode, struct file *file)
 				inode->i_ctime = inode->i_mtime = current_time(inode);
 			spin_lock(&cinode->deferred_lock);
 			cifs_add_deferred_close(cfile, dclose);
-			if (cfile->deferred_scheduled) {
+			if (cfile->deferred_close_scheduled &&
+			    delayed_work_pending(&cfile->deferred)) {
 				mod_delayed_work(deferredclose_wq,
 						&cfile->deferred, cifs_sb->ctx->acregmax);
 			} else {
 				/* Deferred close for files */
 				queue_delayed_work(deferredclose_wq,
 						&cfile->deferred, cifs_sb->ctx->acregmax);
-				cfile->deferred_scheduled = true;
+				cfile->deferred_close_scheduled = true;
 				spin_unlock(&cinode->deferred_lock);
 				return 0;
 			}
@@ -2020,8 +2017,7 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode,
 		if (fsuid_only && !uid_eq(open_file->uid, current_fsuid()))
 			continue;
 		if (OPEN_FMODE(open_file->f_flags) & FMODE_READ) {
-			if ((!open_file->invalidHandle) &&
-				(!open_file->oplock_break_received)) {
+			if ((!open_file->invalidHandle)) {
 				/* found a good file */
 				/* lock it so it will not be closed on us */
 				cifsFileInfo_get(open_file);
@@ -4874,13 +4870,14 @@ void cifs_oplock_break(struct work_struct *work)
 	}
 	/*
 	 * When oplock break is received and there are no active
-	 * file handles but cached, then set the flag oplock_break_received.
+	 * file handles but cached, then schedule deferred close immediately.
 	 * So, new open will not use cached handle.
 	 */
 	spin_lock(&CIFS_I(inode)->deferred_lock);
 	is_deferred = cifs_is_deferred_close(cfile, &dclose);
-	if (is_deferred && cfile->deferred_scheduled) {
-		cfile->oplock_break_received = true;
+	if (is_deferred &&
+	    cfile->deferred_close_scheduled &&
+	    delayed_work_pending(&cfile->deferred)) {
 		mod_delayed_work(deferredclose_wq, &cfile->deferred, 0);
 	}
 	spin_unlock(&CIFS_I(inode)->deferred_lock);
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 524dbdfb7184..cd705f8a4e31 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -672,6 +672,9 @@ cifs_add_pending_open(struct cifs_fid *fid, struct tcon_link *tlink,
 	spin_unlock(&tlink_tcon(open->tlink)->open_file_lock);
 }
 
+/*
+ * Critical section which runs after acquiring deferred_lock.
+ */
 bool
 cifs_is_deferred_close(struct cifsFileInfo *cfile, struct cifs_deferred_close **pdclose)
 {
@@ -688,6 +691,9 @@ cifs_is_deferred_close(struct cifsFileInfo *cfile, struct cifs_deferred_close **
 	return false;
 }
 
+/*
+ * Critical section which runs after acquiring deferred_lock.
+ */
 void
 cifs_add_deferred_close(struct cifsFileInfo *cfile, struct cifs_deferred_close *dclose)
 {
@@ -707,6 +713,9 @@ cifs_add_deferred_close(struct cifsFileInfo *cfile, struct cifs_deferred_close *
 	list_add_tail(&dclose->dlist, &CIFS_I(d_inode(cfile->dentry))->deferred_closes);
 }
 
+/*
+ * Critical section which runs after acquiring deferred_lock.
+ */
 void
 cifs_del_deferred_close(struct cifsFileInfo *cfile)
 {
-- 
2.30.2