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Commit 401b41e5 authored by Anand Jain's avatar Anand Jain Committed by David Sterba
Browse files

btrfs: add framework to handle device flush error as a volume 



This adds comments to the flush error handling part of the code, and
hopes to maintain the same logic with a framework which can be used to
handle the errors at the volume level.

Signed-off-by: default avatarAnand Jain <anand.jain@oracle.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 6b349dfe

fs/btrfs/disk-io.c

+53 −4
Original line number Diff line number Diff line
@@ -3509,6 +3509,10 @@ static int write_dev_flush(struct btrfs_device *device, int wait) 
	if (wait) {

		bio = device->flush_bio;

		if (!bio)

			/*

			 * This means the alloc has failed with ENOMEM, however

			 * here we return 0, as its not a device error.

			 */

			return 0;



		wait_for_completion(&device->flush_wait);
@@ -3548,6 +3552,32 @@ static int write_dev_flush(struct btrfs_device *device, int wait) 
	return 0;

}



static int check_barrier_error(struct btrfs_fs_devices *fsdevs)

{

	int submit_flush_error = 0;

	int dev_flush_error = 0;

	struct btrfs_device *dev;

	int tolerance;



	list_for_each_entry_rcu(dev, &fsdevs->devices, dev_list) {

		if (!dev->bdev) {

			submit_flush_error++;

			dev_flush_error++;

			continue;

		}

		if (dev->last_flush_error == -ENOMEM)

			submit_flush_error++;

		if (dev->last_flush_error && dev->last_flush_error != -ENOMEM)

			dev_flush_error++;

	}



	tolerance = fsdevs->fs_info->num_tolerated_disk_barrier_failures;

	if (submit_flush_error > tolerance || dev_flush_error > tolerance)

		return -EIO;



	return 0;

}



/*

 * send an empty flush down to each device in parallel,

 * then wait for them
@@ -3575,6 +3605,7 @@ static int barrier_all_devices(struct btrfs_fs_info *info) 
		ret = write_dev_flush(dev, 0);

		if (ret)

			errors_send++;

		dev->last_flush_error = ret;

	}



	/* wait for all the barriers */
@@ -3589,12 +3620,30 @@ static int barrier_all_devices(struct btrfs_fs_info *info) 
			continue;



		ret = write_dev_flush(dev, 1);

		if (ret)

		if (ret) {

			dev->last_flush_error = ret;

			errors_wait++;

		}

	if (errors_send > info->num_tolerated_disk_barrier_failures ||

	    errors_wait > info->num_tolerated_disk_barrier_failures)

		return -EIO;

	}



	/*

	 * Try hard in case of flush. Lets say, in RAID1 we have

	 * the following situation

	 *  dev1: EIO dev2: ENOMEM

	 * this is not a fatal error as we hope to recover from

	 * ENOMEM in the next attempt to flush.

	 * But the following is considered as fatal

	 *  dev1: ENOMEM dev2: ENOMEM

	 *  dev1: bdev == NULL dev2: ENOMEM

	 */

	if (errors_send || errors_wait) {

		/*

		 * At some point we need the status of all disks

		 * to arrive at the volume status. So error checking

		 * is being pushed to a separate loop.

		 */

		return check_barrier_error(info->fs_devices);

	}

	return 0;

}

fs/btrfs/volumes.h

+1 −0
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ struct btrfs_device { 
	int missing;

	int can_discard;

	int is_tgtdev_for_dev_replace;

	int last_flush_error;



#ifdef __BTRFS_NEED_DEVICE_DATA_ORDERED

	seqcount_t data_seqcount;