Patch "RAID5: check_reshape() shouldn't call mddev_suspend" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

RAID5: check_reshape() shouldn't call mddev_suspend

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
raid5-check_reshape-shouldn-t-call-mddev_suspend.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Shaohua Li <[email protected]>
Date: Wed, 24 Feb 2016 17:38:28 -0800
Subject: RAID5: check_reshape() shouldn't call mddev_suspend

From: Shaohua Li <[email protected]>

commit 27a353c026a879a1001e5eac4bda75b16262c44a upstream.

check_reshape() is called from raid5d thread. raid5d thread shouldn't call mddev_suspend(), because mddev_suspend() waits for all IO finish but IO is handled in raid5d thread, we could easily deadlock here.

This issue is introduced by
738a273 ("md/raid5: fix allocation of 'scribble' array.")

---
 drivers/md/raid5.c |   18 ++++++++++++++++++
 drivers/md/raid5.h |    2 ++
 2 files changed, 20 insertions(+)

@@ -2089,6 +2089,14 @@ static int resize_chunks(struct r5conf *
 	unsigned long cpu;
 	int err = 0;
 
+	/*
+	 * Never shrink. And mddev_suspend() could deadlock if this is called
+	 * from raid5d. In that case, scribble_disks and scribble_sectors
+	 * should equal to new_disks and new_sectors
+	 */
+	if (conf->scribble_disks >= new_disks &&
+	    conf->scribble_sectors >= new_sectors)
+		return 0;
 	mddev_suspend(conf->mddev);
 	get_online_cpus();
 	for_each_present_cpu(cpu) {

@@ -2110,6 +2118,10 @@ static int resize_chunks(struct r5conf *
 	}
 	put_online_cpus();
 	mddev_resume(conf->mddev);
+	if (!err) {
+		conf->scribble_disks = new_disks;
+		conf->scribble_sectors = new_sectors;
+	}
 	return err;
 }
 

@@ -6413,6 +6425,12 @@ static int raid5_alloc_percpu(struct r5c
 	}
 	put_online_cpus();
 
+	if (!err) {
+		conf->scribble_disks = max(conf->raid_disks,
+			conf->previous_raid_disks);
+		conf->scribble_sectors = max(conf->chunk_sectors,
+			conf->prev_chunk_sectors);
+	}
 	return err;
 }
 

@@ -510,6 +510,8 @@ struct r5conf {
 					      * conversions
 					      */
 	} __percpu *percpu;
+	int scribble_disks;
+	int scribble_sectors;
 #ifdef CONFIG_HOTPLUG_CPU
 	struct notifier_block	cpu_notify;
 #endif

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/raid10-include-bio_end_io_list-in-nr_queued-to-prevent-freeze_array-hang.patch queue-4.5/md-multipath-don-t-hardcopy-bio-in-.make_request-path.patch queue-4.5/raid5-revert-e9e4c377e2f563-to-fix-a-livelock.patch queue-4.5/raid1-include-bio_end_io_list-in-nr_queued-to-prevent-freeze_array-hang.patch queue-4.5/raid5-check_reshape-shouldn-t-call-mddev_suspend.patch queue-4.5/md-raid5-compare-apples-to-apples-or-sectors-to-sectors.patch queue-4.5/md-raid5-preserve-stripe_preread_active-in-break_stripe_batch_list.patch