Re: [PATCH v2 3/6] btrfs: add scrub code and prototypes

[Arne Jansen <sensille@gmx.net>]

Hi David,

thanks for your reviews. I'll update the code accordingly,
comments follow inline.

--
Arne

David Sterba wrote:
> On Fri, Mar 11, 2011 at 03:49:40PM +0100, Arne Jansen wrote:
>> This is the main scrub code.
>>
>> Signed-off-by: Arne Jansen <sensille@gmx.net>
>> ---
>>  fs/btrfs/Makefile |    2 +-
>>  fs/btrfs/ctree.h  |   14 +
>>  fs/btrfs/scrub.c  | 1463 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 1478 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
>> index 31610ea..8fda313 100644
>> --- a/fs/btrfs/Makefile
>> +++ b/fs/btrfs/Makefile
>> @@ -7,4 +7,4 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
>>  	   extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
>>  	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
>>  	   export.o tree-log.o acl.o free-space-cache.o zlib.o lzo.o \
>> -	   compression.o delayed-ref.o relocation.o
>> +	   compression.o delayed-ref.o relocation.o scrub.o
>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>> index 4c99834..030c321 100644
>> --- a/fs/btrfs/ctree.h
>> +++ b/fs/btrfs/ctree.h
>> @@ -2610,4 +2610,18 @@ void btrfs_reloc_pre_snapshot(struct btrfs_trans_handle *trans,
>>  			      u64 *bytes_to_reserve);
>>  void btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
>>  			      struct btrfs_pending_snapshot *pending);
>> +
>> +/* scrub.c */
>> +int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
>> +                    struct btrfs_scrub_progress *progress);
>> +int btrfs_scrub_pause(struct btrfs_root *root);
>> +int btrfs_scrub_pause_super(struct btrfs_root *root);
>> +int btrfs_scrub_continue(struct btrfs_root *root);
>> +int btrfs_scrub_continue_super(struct btrfs_root *root);
>> +int btrfs_scrub_cancel(struct btrfs_root *root);
>> +int btrfs_scrub_cancel_dev(struct btrfs_root *root, struct btrfs_device *dev);
>> +int btrfs_scrub_cancel_devid(struct btrfs_root *root, u64 devid);
>> +int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
>> +                         struct btrfs_scrub_progress *progress);
>> +
>>  #endif
>> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
>> new file mode 100644
>> index 0000000..d606f4d
>> --- /dev/null
>> +++ b/fs/btrfs/scrub.c
>> @@ -0,0 +1,1463 @@
>> +/*
>> + * Copyright (C) 2011 STRATO.  All rights reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public
>> + * License v2 as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public
>> + * License along with this program; if not, write to the
>> + * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
>> + * Boston, MA 021110-1307, USA.
>> + */
>> +
>> +#include <linux/sched.h>
>> +#include <linux/pagemap.h>
>> +#include <linux/writeback.h>
>> +#include <linux/blkdev.h>
>> +#include <linux/rbtree.h>
>> +#include <linux/slab.h>
>> +#include <linux/workqueue.h>
>> +#include "ctree.h"
>> +#include "volumes.h"
>> +#include "disk-io.h"
>> +#include "ordered-data.h"
>> +
>> +/*
>> + * This is only the first step towards a full-features scrub. It reads all
>> + * extent and super block and verifies the checksums. In case a bad checksum
>> + * is found or the extent cannot be read, good data will be written back if
>> + * any can be found.
>> + *
>> + * Future enhancements:
>> + *  - To enhance the performance, better read-ahead strategies for the
>> + *    extent-tree can be employed.
>> + *  - In case an unrepairable extent is encountered, track which files are
>> + *    affected and report them
>> + *  - In case of a read error on files with nodatasum, map the file and read
>> + *    the extent to trigger a writeback of the good copy
>> + *  - track and record media errors, throw out bad devices
>> + *  - add a readonly mode
>> + *  - add a mode to also read unallocated space
>> + */
>> +
>> +#ifdef SCRUB_BTRFS_WORKER
>> +typedef struct btrfs_work scrub_work_t;
>> +#define SCRUB_INIT_WORK(work, fn) do { (work)->func = (fn); } while (0)
>> +#define SCRUB_QUEUE_WORK(wq, w) do { btrfs_queue_worker(&(wq), w); } while (0)
>> +#else
>> +typedef struct work_struct scrub_work_t;
>> +#define SCRUB_INIT_WORK INIT_WORK
>> +#define SCRUB_QUEUE_WORK queue_work
>> +#endif
>> +
>> +struct scrub_bio;
>> +struct scrub_page;
>> +struct scrub_dev;
>> +struct scrub_fixup;
>> +static void scrub_bio_end_io(struct bio *bio, int err);
>> +static void scrub_checksum(scrub_work_t *work);
>> +static int scrub_checksum_data(struct scrub_dev *sdev,
>> +                               struct scrub_page *spag, void *buffer);
>> +static int scrub_checksum_tree_block(struct scrub_dev *sdev,
>> +                                     struct scrub_page *spag, u64 logical,
>> +                                     void *buffer);
>> +static int scrub_checksum_super(struct scrub_bio *sbio, void *buffer);
>> +static void scrub_recheck_end_io(struct bio *bio, int err);
>> +static void scrub_fixup_worker(scrub_work_t *work);
>> +static void scrub_fixup(struct scrub_fixup *fixup);
>> +
>> +#define SCRUB_PAGES_PER_BIO	16	/* 64k per bio */
>> +#define SCRUB_BIOS_PER_DEV	16	/* 1 MB per device in flight */
>> +
>> +struct scrub_page {
>> +	u64			flags;  /* extent flags */
>> +	u64			generation;
>> +	u64			mirror_num;
>> +	int			have_csum;
>> +	u8			csum[BTRFS_CSUM_SIZE];
>> +};
>> +
>> +struct scrub_bio {
>> +	int			index;
>> +	struct scrub_dev	*sdev;
>> +	struct bio		*bio;
>> +	int			err;
>> +	u64			logical;
>> +	u64			physical;
>> +	struct scrub_page	spag[SCRUB_PAGES_PER_BIO];
>> +	u64			count;
>> +	int			next_free;
>> +	scrub_work_t		work;
>> +};
>> +
>> +struct scrub_dev {
>> +	struct scrub_bio	bios[SCRUB_BIOS_PER_DEV];
> 
> sizeof(struct scrub_bio) == 1160
> SCRUB_BIOS_PER_DEV == 16
> 
>> +	struct btrfs_device	*dev;
>> +	int			first_free;
>> +	int			curr;
>> +	atomic_t		in_flight;
>> +	spinlock_t		list_lock;
>> +	wait_queue_head_t	list_wait;
>> +	u16			csum_size;
>> +	struct list_head	csum_list;
>> +	atomic_t		cancel_req;
>> +	/*
>> +	 * statistics
>> +	 */
>> +	struct btrfs_scrub_progress stat;
>> +	spinlock_t		stat_lock;
>> +};
> 
> sizeof(struct scrub_dev) == 18760 on an x86_64, an order 3 allocation in
> scrub_setup_dev()

Is this a problem? There are only few allocations of it, one per device.

> 
>> +
>> +struct scrub_fixup {
>> +	struct scrub_dev	*sdev;
>> +	struct bio		*bio;
>> +	u64			logical;
>> +	u64			physical;
>> +	struct scrub_page	spag;
>> +	scrub_work_t		work;
>> +	int			err;
>> +	int			recheck;
>> +};
>> +
>> +static void scrub_free_csums(struct scrub_dev *sdev)
>> +{
>> +	while(!list_empty(&sdev->csum_list)) {
>> +		struct btrfs_ordered_sum *sum;
>> +		sum = list_first_entry(&sdev->csum_list,
>> +		                       struct btrfs_ordered_sum, list);
>> +		list_del(&sum->list);
>> +		kfree(sum);
>> +	}
>> +}
>> +
>> +static noinline_for_stack void scrub_free_dev(struct scrub_dev *sdev)
>> +{
>> +	int i;
>> +	int j;
>> +	struct page *last_page;
>> +
>> +	if (!sdev)
>> +		return;
>> +
>> +	for (i = 0; i < SCRUB_BIOS_PER_DEV; ++i) {
>> +		struct bio *bio = sdev->bios[i].bio;
>> +		if (bio)
>                    ^^^^^
> stop when we found something to free?
> 

right, good catch. It's obviously the wrong way round.

> 
>> +			break;
>> +		
>> +		last_page = NULL;
>> +		for (j = 0; j < bio->bi_vcnt; ++j) {
>                                 ^^^
> and dereference it.
> 
>> +			if (bio->bi_io_vec[i].bv_page == last_page)
>> +				continue;
>> +			last_page = bio->bi_io_vec[i].bv_page;
>> +			__free_page(last_page);
>> +		}
>> +		bio_put(sdev->bios[i].bio);
>> +	}
>> +
>> +	scrub_free_csums(sdev);
>> +	kfree(sdev);
>> +}
>> +
>> +static noinline_for_stack
>> +struct scrub_dev *scrub_setup_dev(struct btrfs_device *dev)
>> +{
>> +	struct scrub_dev *sdev;
>> +	int		i;
>> +	int		j;
>> +	int		ret;
>> +	struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
> 
> (coding style expects a newline here)

coding style issues are always the gravest. Hope you never catch me with
a line > 80 columns ;)

> 
>> +	sdev = kzalloc(sizeof(*sdev), GFP_NOFS);
>> +	if (!sdev)
>> +		goto nomem;
>> +	sdev->dev = dev;
>> +	for (i = 0; i < SCRUB_BIOS_PER_DEV; ++i) {
>> +		struct bio *bio;
>> +
>> +		bio = bio_alloc(GFP_NOFS, SCRUB_PAGES_PER_BIO);
>> +		if (!bio)
>> +			goto nomem;
>> +
>> +		sdev->bios[i].index = i;
>> +		sdev->bios[i].sdev = sdev;
>> +		sdev->bios[i].bio = bio;
>> +		sdev->bios[i].count = 0;
>> +		SCRUB_INIT_WORK(&sdev->bios[i].work, scrub_checksum);
>> +		bio->bi_private = sdev->bios + i;
>> +		bio->bi_end_io = scrub_bio_end_io;
>> +		bio->bi_sector = 0;
>> +		bio->bi_bdev = dev->bdev;
>> +		bio->bi_size = 0;
>> +
>> +		for (j = 0; j < SCRUB_PAGES_PER_BIO; ++j) {
>> +			struct page *page;
>> +			page = alloc_page(GFP_NOFS);
>> +			if (!page)
>> +				goto nomem;
>> +
>> +			ret = bio_add_page(bio, page, PAGE_SIZE, 0);
>> +			if (!ret)
>> +				goto nomem;
>> +		}
>> +		WARN_ON(bio->bi_vcnt != SCRUB_PAGES_PER_BIO);
>> +
>> +		if (i != SCRUB_BIOS_PER_DEV-1)
>> +			sdev->bios[i].next_free = i + 1;
>> +		 else
>> +			sdev->bios[i].next_free = -1;
>> +	}
>> +	sdev->first_free = 0;
>> +	sdev->curr = -1;
>> +	atomic_set(&sdev->in_flight, 0);
>> +	atomic_set(&sdev->cancel_req, 0);
>> +	sdev->csum_size = btrfs_super_csum_size(&fs_info->super_copy);
>> +	INIT_LIST_HEAD(&sdev->csum_list);
>> +	
>> +	spin_lock_init(&sdev->list_lock);
>> +	spin_lock_init(&sdev->stat_lock);
>> +	init_waitqueue_head(&sdev->list_wait);
>> +	return sdev;
>> +
>> +nomem:
>> +	scrub_free_dev(sdev);
> 
> When taking the 'goto nomem' path, either all bios are leaked, or the
> check in scrub_free_dev is buggy ...
> 
>> +	return ERR_PTR(-ENOMEM);
>> +}
>> +
>> +/*
>> + * scrub_recheck_error gets called when either verification of the page
>> + * failed or the bio failed to read, e.g. with EIO. In the latter case,
>> + * recheck_error gets called for every page in the bio, even though only
>> + * one may be bad
>> + */
>> +static void scrub_recheck_error(struct scrub_bio *sbio, int ix)
>> +{
>> +	struct scrub_dev *sdev = sbio->sdev;
>> +	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
>> +	struct bio *bio = NULL;
>> +	struct page *page = NULL;
>> +	struct scrub_fixup *fixup = NULL;
>> +	int ret;
>> +
>> +	/*
>> +	 * while we're in here we do not want the transaction to commit.
>> +	 * To prevent it, we increment scrubs_running. scrub_pause will
>> +	 * have to wait until we're finished
>> +	 */
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	atomic_inc(&fs_info->scrubs_running);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +
>> +	fixup = kzalloc(sizeof(*fixup), GFP_NOFS);
>> +	if (!fixup)
>> +		goto malloc_error;
>> +
>> +	fixup->logical = sbio->logical + ix * PAGE_SIZE;
>> +	fixup->physical = sbio->physical + ix * PAGE_SIZE;
>> +	fixup->spag = sbio->spag[ix];
>> +	fixup->sdev = sdev;
>> +
>> +	bio = bio_alloc(GFP_NOFS, 1);
>> +	if (!bio)
>> +		goto malloc_error;
>> +	bio->bi_private = fixup;
>> +	bio->bi_size = 0;
>> +	bio->bi_bdev = sdev->dev->bdev;	/* FIXME: temporary for add_page */
>> +	fixup->bio = bio;
>> +	fixup->recheck = 0;
>> +
>> +	page = alloc_page(GFP_NOFS);
>> +	if (!page)
>> +		goto malloc_error;
>> +
>> +	ret = bio_add_page(bio, page, PAGE_SIZE, 0);
>> +	if (!ret)
>> +		goto malloc_error;
>> +
>> +	if (!sbio->err) {
>> +		/*
>> +		 * shorter path: just a checksum error, go ahead and correct it
>> +		 */
>> +		scrub_fixup_worker(&fixup->work);
>> +		return;
>> +	}
>> +
>> +	/*
>> +	 * an I/O-error occured for one of the blocks in the bio, not
>> +	 * necessarily for this one, so first try to read it separately
>> +	 */
>> +	SCRUB_INIT_WORK(&fixup->work, scrub_fixup_worker);
>> +	fixup->recheck = 1;
>> +	bio->bi_end_io = scrub_recheck_end_io;
>> +	bio->bi_sector = fixup->physical >> 9;
>> +	bio->bi_bdev = sdev->dev->bdev;
>> +	submit_bio(0, bio);
>> +
>> +	return;
>> +
>> +malloc_error:
>> +	if (bio) 
>> +		bio_put(bio);
>> +	if (page)
>> +		__free_page(page);
>> +	if (fixup)
>> +		kfree(fixup);
>> +	spin_lock(&sdev->stat_lock);
>> +	++sdev->stat.malloc_errors;
>> +	spin_unlock(&sdev->stat_lock);
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	atomic_dec(&fs_info->scrubs_running);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +	wake_up(&fs_info->scrub_pause_wait);
>> +}
>> +
>> +static void scrub_recheck_end_io(struct bio *bio, int err)
>> +{
>> +	struct scrub_fixup *fixup = bio->bi_private;
>> +	struct btrfs_fs_info *fs_info = fixup->sdev->dev->dev_root->fs_info;
>> +
>> +	fixup->err = err;
>> +	SCRUB_QUEUE_WORK(fs_info->scrub_workers, &fixup->work);
>> +}
>> +
>> +static int scrub_fixup_check(struct scrub_fixup *fixup)
>> +{
>> +	int ret = 1;
>> +	struct page *page;
>> +	void *buffer;
>> +	u64 flags = fixup->spag.flags;
>> +
>> +	page = fixup->bio->bi_io_vec[0].bv_page;
>> +	buffer = kmap_atomic(page, KM_USER0);
>> +	if (flags & BTRFS_EXTENT_FLAG_DATA) {
>> +		ret = scrub_checksum_data(fixup->sdev,
>> +					  &fixup->spag, buffer);
>> +	} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
>> +		ret = scrub_checksum_tree_block(fixup->sdev,
>> +						&fixup->spag,
>> +						fixup->logical,
>> +						buffer);
>> +	} else {
>> +		WARN_ON(1);
>> +	}
>> +	kunmap_atomic(buffer, KM_USER0);
>> +
>> +	return ret;
>> +}
>> +
>> +static void scrub_fixup_worker(scrub_work_t *work)
>> +{
>> +	struct scrub_fixup *fixup;
>> +	struct btrfs_fs_info *fs_info;
>> +	u64 flags;
>> +	int ret = 1;
>> +
>> +	fixup = container_of(work, struct scrub_fixup, work);
>> +	fs_info = fixup->sdev->dev->dev_root->fs_info;
>> +	flags = fixup->spag.flags;
>> +
>> +	if (fixup->recheck && fixup->err == 0)
>> +		ret = scrub_fixup_check(fixup);
>> +
>> +	if (ret || fixup->err)
>> +		scrub_fixup(fixup);
>> +
>> +	__free_page(fixup->bio->bi_io_vec[0].bv_page);
>> +	bio_put(fixup->bio);
>> +
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	atomic_dec(&fs_info->scrubs_running);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +	wake_up(&fs_info->scrub_pause_wait);
>> +
>> +	kfree(fixup);
>> +}
>> +
>> +static void scrub_fixup_end_io(struct bio *bio, int err)
>> +{
>> +	complete((struct completion *)bio->bi_private);
>> +}
>> +
>> +static void scrub_fixup(struct scrub_fixup *fixup)
>> +{
>> +	struct scrub_dev *sdev = fixup->sdev;
>> +	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
>> +	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree; 
>> +	struct btrfs_multi_bio *multi = NULL;
>> +	struct bio *bio = fixup->bio;
>> +	u64 length;
>> +	int i;
>> +	int ret;
>> +	DECLARE_COMPLETION_ONSTACK(complete);
>> +
>> +	if ((fixup->spag.flags & BTRFS_EXTENT_FLAG_DATA) &&
>> +	    (fixup->spag.have_csum == 0)) {
>> +		/*
>> +		 * nodatasum, don't try to fix anything
>> +		 * FIXME: we can do better, open the inode and trigger a
>> +		 * writeback
>> +		 */
>> +		goto uncorrectable;
>> +	}
>> +
>> +	length = PAGE_SIZE;
>> +	ret = btrfs_map_block(map_tree, REQ_WRITE, fixup->logical, &length,
>> +	                      &multi, 0);
>> +	if (ret || !multi || length < PAGE_SIZE) {
>> +		printk(KERN_ERR
>> +		       "scrub_fixup: btrfs_map_block failed us for %lld\n",
>> +		       fixup->logical);
>> +		WARN_ON(1);
>> +		return;
>> +	}
>> +
>> +	if (multi->num_stripes == 1) {
>> +		/* there aren't any replicas */
>> +		goto uncorrectable;
>> +	}
>> +
>> +	/*
>> +	 * first find a good copy
>> +	 */
>> +	for (i = 0; i < multi->num_stripes; ++i) {
>> +		if (i == fixup->spag.mirror_num)
>> +			continue;
>> +
>> +		bio->bi_sector = multi->stripes[i].physical >> 9;
>> +		bio->bi_bdev = multi->stripes[i].dev->bdev;
>> +		bio->bi_size = PAGE_SIZE;
>> +		bio->bi_next = NULL;
>> +		bio->bi_flags = 1 << BIO_UPTODATE;
>> +		bio->bi_comp_cpu = -1;
>> +		bio->bi_end_io = scrub_fixup_end_io;
>> +		bio->bi_private = &complete;
>> +
>> +		submit_bio(0, bio);
>> +
>> +		wait_for_completion(&complete);
>> +
>> +		if (~bio->bi_flags & BIO_UPTODATE)
>> +			/* I/O-error, this is not a good copy */
>> +			continue;
>> +
>> +		ret = scrub_fixup_check(fixup);
>> +		if (ret == 0)
>> +			break;
>> +	}
>> +	if (i == multi->num_stripes)
>> +		goto uncorrectable;
>> +
>> +	/*
>> +	 * the bio now contains good data, write it back
>> +	 */
>> +	bio->bi_sector = fixup->physical >> 9;
>> +	bio->bi_bdev = sdev->dev->bdev;
>> +	bio->bi_size = PAGE_SIZE;
>> +	bio->bi_next = NULL;
>> +	bio->bi_flags = 1 << BIO_UPTODATE;
>> +	bio->bi_comp_cpu = -1;
>> +	bio->bi_end_io = scrub_fixup_end_io;
>> +	bio->bi_private = &complete;
>> +
>> +	submit_bio(REQ_WRITE, bio);
>> +
>> +	wait_for_completion(&complete);
>> +
>> +	if (~bio->bi_flags & BIO_UPTODATE)
>> +		/* I/O-error, writeback failed, give up */
>> +		goto uncorrectable;
>> +
>> +	kfree(multi);
>> +	spin_lock(&sdev->stat_lock);
>> +	++sdev->stat.corrected_errors;
>> +	spin_unlock(&sdev->stat_lock);
>> +
>> +	if (printk_ratelimit())
>> +		printk(KERN_ERR "btrfs: fixed up at %lld\n", fixup->logical);
>> +	return;
>> +
>> +uncorrectable:
>> +	kfree(multi);
>> +	spin_lock(&sdev->stat_lock);
>> +	++sdev->stat.uncorrectable_errors;
>> +	spin_unlock(&sdev->stat_lock);
>> +
>> +	if (printk_ratelimit())
>> +		printk(KERN_ERR "btrfs: unable to fixup at %lld\n",
>> +			 fixup->logical);
>> +}
>> +
>> +static void scrub_bio_end_io(struct bio *bio, int err)
>> +{
>> +	struct scrub_bio *sbio = bio->bi_private;
>> +	struct scrub_dev *sdev = sbio->sdev;
>> +	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
>> +
>> +	sbio->err = err;
>> +
>> +	SCRUB_QUEUE_WORK(fs_info->scrub_workers, &sbio->work);
>> +}
>> +
>> +static void scrub_checksum(scrub_work_t *work)
>> +{
>> +	struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
>> +	struct scrub_dev *sdev = sbio->sdev;
>> +	struct page *page;
>> +	void *buffer;
>> +	int i;
>> +	u64 flags;
>> +	u64 logical;
>> +	int ret;
>> +
>> +	if (sbio->err) {
>> +		for (i = 0; i < sbio->count; ++i) {
>> +			scrub_recheck_error(sbio, i);
>> +		}
>> +		spin_lock(&sdev->stat_lock);
>> +		++sdev->stat.read_errors;
>> +		spin_unlock(&sdev->stat_lock);
>> +		goto out;
>> +	}
>> +	for (i = 0; i < sbio->count; ++i) {
>> +		page = sbio->bio->bi_io_vec[i].bv_page;
>> +		buffer = kmap_atomic(page, KM_USER0);
>> +		flags = sbio->spag[i].flags;
>> +		logical = sbio->logical + i * PAGE_SIZE;
>> +		ret = 0;
>> +		if (flags & BTRFS_EXTENT_FLAG_DATA) {
>> +			ret = scrub_checksum_data(sdev, sbio->spag + i, buffer);
>> +		} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
>> +			ret = scrub_checksum_tree_block(sdev, sbio->spag + i,
>> +			                                logical, buffer);
>> +		} else if (flags & BTRFS_EXTENT_FLAG_SUPER) {
>> +			BUG_ON(i);
>> +			(void)scrub_checksum_super(sbio, buffer);
>> +		} else {
>> +			WARN_ON(1);
>> +		}
>> +		kunmap_atomic(buffer, KM_USER0);
>> +		if (ret)
>> +			scrub_recheck_error(sbio, i);
>> +	}
>> +
>> +out:
>> +	spin_lock(&sdev->list_lock);
>> +	sbio->next_free = sdev->first_free;
>> +	sdev->first_free = sbio->index;
>> +	spin_unlock(&sdev->list_lock);
>> +	atomic_dec(&sdev->in_flight);
>> +	wake_up(&sdev->list_wait);
>> +}
>> +
>> +static int scrub_checksum_data(struct scrub_dev *sdev,
>> +                               struct scrub_page *spag, void *buffer)
>> +{
>> +	u8 csum[BTRFS_CSUM_SIZE];
>> +	u32 crc = ~(u32)0;
>> +	int fail = 0;
>> +	struct btrfs_root *root = sdev->dev->dev_root;
>> +
>> +	if (!spag->have_csum)
>> +		return 0;
>> +
>> +	crc = btrfs_csum_data(root, buffer, crc, PAGE_SIZE);
>> +	btrfs_csum_final(crc, csum);
>> +	if (memcmp(csum, spag->csum, sdev->csum_size))
>> +		fail = 1;
>> +
>> +	spin_lock(&sdev->stat_lock);
>> +	++sdev->stat.data_extents_scrubbed;
>> +	sdev->stat.data_bytes_scrubbed += PAGE_SIZE;
>> +	if (fail)
>> +		++sdev->stat.csum_errors;
>> +	spin_unlock(&sdev->stat_lock);
>> +
>> +	return fail;
>> +}
>> +
>> +static int scrub_checksum_tree_block(struct scrub_dev *sdev,
>> +                                     struct scrub_page *spag, u64 logical,
>> +                                     void *buffer)
>> +{
>> +	struct btrfs_header *h;
>> +	struct btrfs_root *root = sdev->dev->dev_root;
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	u8 csum[BTRFS_CSUM_SIZE];
>> +	u32 crc = ~(u32)0;
>> +	int fail = 0;
>> +	int crc_fail = 0;
>> +
>> +	/*
>> +	 * we don't use the getter functions here, as we
>> +	 * a) don't have an extent buffer and
>> +	 * b) the page is already kmapped
>> +	 */
>> +	h = (struct btrfs_header *)buffer;
>> +
>> +	if (logical != le64_to_cpu(h->bytenr))
>> +		++fail;
>> +
>> +	if (spag->generation != le64_to_cpu(h->generation))
>> +		++fail;
>> +
>> +	if (memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
>> +		++fail;
>> +
>> +	if (memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
>> +	           BTRFS_UUID_SIZE))
>> +		++fail;
>> +
>> +	crc = btrfs_csum_data(root, buffer + BTRFS_CSUM_SIZE, crc,
>> +	                      PAGE_SIZE - BTRFS_CSUM_SIZE);
>> +	btrfs_csum_final(crc, csum);
>> +	if (memcmp(csum, h->csum, sdev->csum_size))
>> +		++crc_fail;
>> +
>> +	spin_lock(&sdev->stat_lock);
>> +	++sdev->stat.tree_extents_scrubbed;
>> +	sdev->stat.tree_bytes_scrubbed += PAGE_SIZE;
>> +	if (crc_fail)
>> +		++sdev->stat.csum_errors;
>> +	if (fail)
>> +		++sdev->stat.verify_errors;
>> +	spin_unlock(&sdev->stat_lock);
>> +
>> +	return (fail || crc_fail);
>> +}
>> +
>> +static int scrub_checksum_super(struct scrub_bio *sbio, void *buffer)
>> +{
>> +	struct btrfs_super_block *s;
>> +	u64 logical;
>> +	struct scrub_dev *sdev = sbio->sdev;
>> +	struct btrfs_root *root = sdev->dev->dev_root;
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	u8 csum[BTRFS_CSUM_SIZE];
>> +	u32 crc = ~(u32)0;
>> +	int fail = 0;
>> +
>> +	s = (struct btrfs_super_block *)buffer;
>> +	logical = sbio->logical;
>> +
>> +	if (logical != le64_to_cpu(s->bytenr))
>> +		++fail;
>> +
>> +	if (sbio->spag[0].generation != le64_to_cpu(s->generation))
>> +		++fail;
>> +
>> +	if (memcmp(s->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
>> +		++fail;
>> +
>> +	crc = btrfs_csum_data(root, buffer + BTRFS_CSUM_SIZE, crc,
>> +	                      PAGE_SIZE - BTRFS_CSUM_SIZE);
>> +	btrfs_csum_final(crc, csum);
>> +	if (memcmp(csum, s->csum, sbio->sdev->csum_size))
>> +		++fail;
>> +
>> +	if (fail) {
>> +		/*
>> +		 * if we find an error in a super block, we just report it.
>> +		 * They will get written with the next transaction commit
>> +		 * anyway
>> +		 */
>> +		spin_lock(&sdev->stat_lock);
>> +		++sdev->stat.super_errors;
>> +		spin_unlock(&sdev->stat_lock);
>> +	}
>> +
>> +	return fail;
>> +}
>> +
>> +static int scrub_submit(struct scrub_dev *sdev)
>> +{
>> +	struct scrub_bio *sbio;
>> +
>> +	if (sdev->curr == -1)
>> +		return 0;
>> +
>> +	sbio = sdev->bios + sdev->curr;
>> +	
>> +	sbio->bio->bi_sector = sbio->physical >> 9;
>> +	sbio->bio->bi_size = sbio->count * PAGE_SIZE;
>> +	sbio->bio->bi_next = NULL;
>> +	sbio->bio->bi_flags = 1 << BIO_UPTODATE;
>> +	sbio->bio->bi_comp_cpu = -1;
>> +	sbio->bio->bi_bdev = sdev->dev->bdev;
>> +	sdev->curr = -1;
>> +	atomic_inc(&sdev->in_flight);
>> +
>> +	submit_bio(0, sbio->bio);
>> +
>> +	return 0;
>> +}
>> +
>> +static int scrub_page(struct scrub_dev *sdev, u64 logical, u64 len,
>> +                      u64 physical, u64 flags, u64 gen, u64 mirror_num,
>> +                      u8 *csum, int force)
>> +{
>> +	struct scrub_bio *sbio;
>> +again:
>> +	/*
>> +	 * grab a fresh bio or wait for one to become available
>> +	 */
>> +	while (sdev->curr == -1) {
>> +		unsigned long flags;
>> +		spin_lock_irqsave(&sdev->list_lock, flags);
> 
> Is this called from an interrupt or why is the _irqsave variant used?

You're right, it is not needed anymore. It used to get locked directly
from the end_io callback, but now everything is deferred to workers.

> 
>> +		sdev->curr = sdev->first_free;
>> +		if (sdev->curr != -1) {
>> +			sdev->first_free = sdev->bios[sdev->curr].next_free;
>> +			sdev->bios[sdev->curr].next_free = -1;
>> +			sdev->bios[sdev->curr].count = 0;
>> +			spin_unlock_irqrestore(&sdev->list_lock, flags);
>> +		} else {
>> +			spin_unlock_irqrestore(&sdev->list_lock, flags);
>> +			wait_event(sdev->list_wait, sdev->first_free != -1);
>> +		}
>> +	}
>> +	sbio = sdev->bios + sdev->curr;
>> +	if (sbio->count == 0) {
>> +		sbio->physical = physical;
>> +		sbio->logical = logical;
>> +	} else if (sbio->physical + sbio->count * PAGE_SIZE != physical) {
>> +		scrub_submit(sdev);
>> +		goto again;
>> +	}
>> +	sbio->spag[sbio->count].flags = flags;
>> +	sbio->spag[sbio->count].generation = gen;
>> +	sbio->spag[sbio->count].have_csum = 0;
>> +	sbio->spag[sbio->count].mirror_num = mirror_num;
>> +	if (csum) {
>> +		sbio->spag[sbio->count].have_csum = 1;
>> +		memcpy(sbio->spag[sbio->count].csum, csum, sdev->csum_size);
>> +	}
>> +	++sbio->count;
>> +	if (sbio->count == SCRUB_PAGES_PER_BIO || force)
>> +		scrub_submit(sdev);
>> +		
>> +	return 0;
>> +}
>> +
>> +static int scrub_find_csum(struct scrub_dev *sdev, u64 logical, u64 len,
>> +                           u8 *csum)
>> +{
>> +	struct btrfs_ordered_sum *sum = NULL;
>> +	int ret = 0;
>> +	unsigned long i;
>> +	unsigned long num_sectors;
>> +	u32 sectorsize = sdev->dev->dev_root->sectorsize;
>> +
>> +	while (!list_empty(&sdev->csum_list)) {
>> +		sum = list_first_entry(&sdev->csum_list,
>> +				       struct btrfs_ordered_sum, list);
>> +		if (sum->bytenr > logical)
>> +			return 0;
>> +		if (sum->bytenr + sum->len > logical)
>> +			break;
>> +
>> +		++sdev->stat.csum_discards;
>> +		list_del(&sum->list);
>> +		kfree(sum);
>> +		sum = NULL;
>> +	}
>> +	if (!sum)
>> +		return 0;
>> +
>> +	num_sectors = sum->len / sectorsize;
>> +	for (i = 0; i < num_sectors; ++i) {
>> +		if (sum->sums[i].bytenr == logical) {
>> +			memcpy(csum, &sum->sums[i].sum, sdev->csum_size);
>> +			ret = 1;
>> +			break;
>> +		}
>> +	}
>> +	if (ret && i == num_sectors - 1) {
>> +		list_del(&sum->list);
>> +		kfree(sum);
>> +	}
>> +	return ret;
>> +}
>> +
>> +/* scrub extent tries to collect up to 64 kB for each bio */
>> +static int scrub_extent(struct scrub_dev *sdev, u64 logical, u64 len,
>> +                        u64 physical, u64 flags, u64 gen, u64 mirror_num)
>> +{
>> +	int ret;
>> +	u8 csum[BTRFS_CSUM_SIZE];
>> +
>> +	while(len) {
>> +		u64 l = min_t(u64, len, PAGE_SIZE);
>> +		int have_csum = 0;
>> +
>> +		if (flags & BTRFS_EXTENT_FLAG_DATA) {
>> +			/* push csums to sbio */
>> +			have_csum = scrub_find_csum(sdev, logical, l, csum);
>> +			if (have_csum == 0)
>> +				++sdev->stat.no_csum;
>> +		}
>> +		ret = scrub_page(sdev, logical, l, physical, flags, gen,
>> +		                 mirror_num, have_csum ? csum : NULL, 0);
>> +		if (ret)
>> +			return ret;
>> +		len -= l;
>> +		logical += l;
>> +		physical += l;
>> +	}
>> +	return 0;
>> +}
>> +
>> +static noinline_for_stack int scrub_stripe(struct scrub_dev *sdev,
>> +	struct map_lookup *map, int num, u64 base, u64 length)
>> +{
>> +	struct btrfs_path *path;
>> +	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
>> +	struct btrfs_root *root = fs_info->extent_root;
>> +	struct btrfs_root *csum_root = fs_info->csum_root;
>> +	struct btrfs_extent_item *extent;
>> +	u64 flags;
>> +	int ret;
>> +	int slot;
>> +	int i;
>> +	int nstripes;
>> +	int start_stripe;
>> +	struct extent_buffer *l;
>> +	struct btrfs_key key;
>> +	u64 physical;
>> +	u64 logical;
>> +	u64 generation;
>> +	u64 mirror_num;
>> +
>> +	u64 increment = map->stripe_len;
>> +	u64 offset;
>> +
>> +	nstripes = length;
>> +	offset = 0;
>> +	do_div(nstripes, map->stripe_len);
>> +	if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
>> +		offset = map->stripe_len * num;
>> +		increment = map->stripe_len * map->num_stripes;
>> +		mirror_num = 0;
>> +	} else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
>> +		int factor = map->num_stripes / map->sub_stripes;
>> +		offset = map->stripe_len * (num / map->sub_stripes);
>> +		increment = map->stripe_len * factor;
>> +		mirror_num = num % map->sub_stripes;
>> +	} else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
>> +		increment = map->stripe_len;
>> +		mirror_num = num % map->num_stripes;
>> +	} else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
>> +		increment = map->stripe_len;
>> +		mirror_num = num % map->num_stripes;
>> +	} else {
>> +		increment = map->stripe_len;
>> +		mirror_num = 0;
>> +	}
>> +
>> +	path = btrfs_alloc_path();
>> +	if (!path)
>> +		return -ENOMEM;
>> +
>> +	path->reada = 2;
>> +	path->search_commit_root = 1;
>> +	path->skip_locking = 1;
>> +
>> +	/*
>> +	 * find all extents for each stripe and just read them to get
>> +	 * them into the page cache
>> +	 * FIXME: we can do better. build a more intelligent prefetching
>> +	 */
>> +	logical = base + offset;
>> +	physical = map->stripes[num].physical;
>> +	ret = 0;
>> +	for (i = 0; i < nstripes; ++i) {
>> +		key.objectid = logical;
>> +		key.type = BTRFS_EXTENT_ITEM_KEY;
>> +		key.offset = (u64)0;
>> +
>> +		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
>> +		if (ret < 0)
>> +			goto out;
>> +
>> +		l = path->nodes[0];
>> +		slot = path->slots[0];
>> +		btrfs_item_key_to_cpu(l, &key, slot);
>> +		if (key.objectid != logical) {
>> +			ret = btrfs_previous_item(root, path, 0,
>> +			                          BTRFS_EXTENT_ITEM_KEY);
>> +			if (ret < 0)
>> +				goto out;
>> +		}
>> +
>> +		while (1) {
>> +			l = path->nodes[0];
>> +			slot = path->slots[0];
>> +			if (slot >= btrfs_header_nritems(l)) {
>> +				ret = btrfs_next_leaf(root, path);
>> +				if (ret == 0)
>> +					continue;
>> +				if (ret < 0)
>> +					goto out;
>> +
>> +				break;
>> +			}
>> +			btrfs_item_key_to_cpu(l, &key, slot);
>> +
>> +			if (key.objectid + key.offset <= logical)
>> +				goto next1;
>> +
>> +			if (key.objectid >= logical + map->stripe_len)
>> +				break;
>> +next1:
>> +			path->slots[0]++;
>> +		}
>> +		btrfs_release_path(root, path);
>> +		logical += increment;
>> +		physical += map->stripe_len;
>> +		cond_resched();
>> +	}
>> +
>> +	/*
>> +	 * collect all data csums for the stripe to avoid seeking during
>> +	 * the scrub. This might currently (crc32) end up to be about 1MB
>> +	 */
>> +	start_stripe = 0;
>> +again:
>> +	logical = base + offset + start_stripe * map->stripe_len;
>> +	physical = map->stripes[num].physical + start_stripe * map->stripe_len;
>> +	for (i = start_stripe; i < nstripes; ++i) {
>> +		ret = btrfs_lookup_csums_range(csum_root, logical,
>> +		                               logical + map->stripe_len - 1,
>> +		                               &sdev->csum_list, 1);
>> +		if (ret)
>> +			goto out;
>> +
>> +		logical += increment;
>> +		cond_resched();
>> +	}
>> +	/*
>> +	 * now find all extents for each stripe and scrub them
>> +	 */
>> +	logical = base + offset + start_stripe * map->stripe_len;
>> +	physical = map->stripes[num].physical + start_stripe * map->stripe_len;
>> +	ret = 0;
>> +	for (i = start_stripe; i < nstripes; ++i) {
>> +		/*
>> +		 * canceled?
>> +		 */
>> +		if (atomic_read(&fs_info->scrub_cancel_req) ||
>> +		    atomic_read(&sdev->cancel_req)) {
>> +			ret = -ECANCELED;
>> +			goto out;
>> +		}
>> +		/*
>> +		 * check to see if we have to pause
>> +		 */
>> +		if (atomic_read(&fs_info->scrub_pause_req)) {
>> +			/* push queued extents */
>> +			scrub_submit(sdev);
>> +			wait_event(sdev->list_wait,
>> +			           atomic_read(&sdev->in_flight) == 0);
>> +			atomic_inc(&fs_info->scrubs_paused);
>> +			wake_up(&fs_info->scrub_pause_wait);
>> +			mutex_lock(&fs_info->scrub_lock);
>> +			while(atomic_read(&fs_info->scrub_pause_req)) {
>> +				mutex_unlock(&fs_info->scrub_lock);
>> +				wait_event(fs_info->scrub_pause_wait,
>> +				   atomic_read(&fs_info->scrub_pause_req) == 0);
>> +				mutex_lock(&fs_info->scrub_lock);
>> +			}
>> +			atomic_dec(&fs_info->scrubs_paused);
>> +			mutex_unlock(&fs_info->scrub_lock);
>> +			wake_up(&fs_info->scrub_pause_wait);
>> +			scrub_free_csums(sdev);
>> +			goto again;
>> +		}
>> +
>> +		key.objectid = logical;
>> +		key.type = BTRFS_EXTENT_ITEM_KEY;
>> +		key.offset = (u64)0;
>> +
>> +		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
>> +		if (ret < 0)
>> +			goto out;
>> +
>> +		l = path->nodes[0];
>> +		slot = path->slots[0];
>> +		btrfs_item_key_to_cpu(l, &key, slot);
>> +		if (key.objectid != logical) {
>> +			ret = btrfs_previous_item(root, path, 0,
>> +			                          BTRFS_EXTENT_ITEM_KEY);
>> +			if (ret < 0)
>> +				goto out;
>> +		}
>> +
>> +		while (1) {
>> +			l = path->nodes[0];
>> +			slot = path->slots[0];
>> +			if (slot >= btrfs_header_nritems(l)) {
>> +				ret = btrfs_next_leaf(root, path);
>> +				if (ret == 0)
>> +					continue;
>> +				if (ret < 0)
>> +					goto out;
>> +
>> +				break;
>> +			}
>> +			btrfs_item_key_to_cpu(l, &key, slot);
>> +
>> +			if (key.objectid + key.offset <= logical)
>> +				goto next;
>> +
>> +			if (key.objectid >= logical + map->stripe_len)
>> +				break;
>> +
>> +			if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY)
>> +				goto next;
>> +
>> +			extent = btrfs_item_ptr(l, slot,
>> +			                        struct btrfs_extent_item);
>> +			flags = btrfs_extent_flags(l, extent);
>> +			generation = btrfs_extent_generation(l, extent);
>> +
>> +			if (key.objectid < logical &&
>> +			    (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
>> +				printk(KERN_ERR
>> +				       "btrfs scrub: tree block %lld spanning "
>> +				       "stripes, ignored. logical=%lld\n",
>> +				       key.objectid, logical);
>> +				goto next;
>> +			}
>> +
>> +			/*
>> +			 * trim extent to this stripe
>> +			 */
>> +			if (key.objectid < logical) {
>> +				key.offset -= logical - key.objectid;
>> +				key.objectid = logical;
>> +			}
>> +			if (key.objectid + key.offset >
>> +			    logical + map->stripe_len) {
>> +				key.offset = logical + map->stripe_len -
>> +				             key.objectid;
>> +			}
>> +
>> +			ret = scrub_extent(sdev, key.objectid, key.offset,
>> +			                   key.objectid - logical + physical,
>> +			                   flags, generation, mirror_num);
>> +			if (ret)
>> +				goto out;
>> +next:
>> +			path->slots[0]++;
>> +		}
>> +		btrfs_release_path(root, path);
>> +		logical += increment;
>> +		physical += map->stripe_len;
>> +		spin_lock(&sdev->stat_lock);
>> +		sdev->stat.last_physical = physical;
>> +		spin_unlock(&sdev->stat_lock);
>> +	}
>> +	/* push queued extents */
>> +	scrub_submit(sdev);
>> +
>> +out:
>> +	btrfs_free_path(path);
>> +	return ret < 0 ? ret : 0;
>> +}
>> +
>> +static noinline_for_stack int scrub_chunk(struct scrub_dev *sdev, 
>> +	u64 chunk_tree, u64 chunk_objectid, u64 chunk_offset, u64 length)
>> +{
>> +	struct btrfs_mapping_tree *map_tree =
>> +		&sdev->dev->dev_root->fs_info->mapping_tree;
>> +	struct map_lookup *map;
>> +	struct extent_map *em;
>> +	int i;
>> +	int ret;
>> +
>> +	read_lock(&map_tree->map_tree.lock);
>> +	em = lookup_extent_mapping(&map_tree->map_tree, chunk_offset, 1);
>> +	read_unlock(&map_tree->map_tree.lock);
>> +
>> +	if (!em)
>> +		return -EINVAL;
>> +
>> +	map = (struct map_lookup *)em->bdev;
>> +	if (em->start != chunk_offset)
>> +		return -EINVAL;
>> +
>> +	if (em->len < length)
>> +		return -EINVAL;
>> +
>> +	for (i = 0; i < map->num_stripes; ++i) {
>> +		if (map->stripes[i].dev == sdev->dev) {
>> +			ret = scrub_stripe(sdev, map, i, chunk_offset, length);
>> +			if (ret)
>> +				return ret;
>> +		}
>> +	}
>> +	return 0;
>> +}
>> +
>> +static noinline_for_stack
>> +int scrub_enumerate_chunks(struct scrub_dev *sdev, u64 start, u64 end)
>> +{
>> +	struct btrfs_dev_extent *dev_extent = NULL;
>> +	struct btrfs_path *path;
>> +	struct btrfs_root *root = sdev->dev->dev_root;
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	u64 length;
>> +	u64 chunk_tree;
>> +	u64 chunk_objectid;
>> +	u64 chunk_offset;
>> +	int ret;
>> +	int slot;
>> +	struct extent_buffer *l;
>> +	struct btrfs_key key;
>> +	struct btrfs_key found_key;
>> +	struct btrfs_block_group_cache *cache;
>> +
>> +	path = btrfs_alloc_path();
>> +	if (!path)
>> +		return -ENOMEM;
>> +
>> +	path->reada = 2;
>> +	path->search_commit_root = 1;
>> +	path->skip_locking = 1;
>> +
>> +	key.objectid = sdev->dev->devid;
>> +	key.offset = 0ull;
>> +	key.type = BTRFS_DEV_EXTENT_KEY;
>> +
>> +
>> +	while (1) {
>> +		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
>> +		if (ret < 0)
>> +			goto out;
>> +		ret = 0;
>> +
>> +		l = path->nodes[0];
>> +		slot = path->slots[0];
>> +
>> +		btrfs_item_key_to_cpu(l, &found_key, slot);
>> +
>> +		if (found_key.objectid != sdev->dev->devid)
>> +			break;
>> +
>> +		if (btrfs_key_type(&key) != BTRFS_DEV_EXTENT_KEY)
>> +			break;
>> +
>> +		if (found_key.offset >= end)
>> +			break;
>> +
>> +		if (found_key.offset < key.offset)
>> +			break;
>> +
>> +		dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
>> +		length = btrfs_dev_extent_length(l, dev_extent);
>> +
>> +		if (found_key.offset + length <= start) {
>> +			key.offset = found_key.offset + length;
>> +			btrfs_release_path(root, path);
>> +			continue;
>> +		}
>> +
>> +		chunk_tree = btrfs_dev_extent_chunk_tree(l, dev_extent);
>> +		chunk_objectid = btrfs_dev_extent_chunk_objectid(l, dev_extent);
>> +		chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
>> +
>> +		/*
>> +		 * get a reference on the corresponding block group to prevent
>> +		 * the chunk from going away while we scrub it
>> +		 */
>> +		cache = btrfs_lookup_block_group(fs_info, chunk_offset);
>> +		if (!cache) {
>> +			ret = -ENOENT;
>> +			goto out;
>> +		}
>> +		ret = scrub_chunk(sdev, chunk_tree, chunk_objectid,
>> +		                  chunk_offset, length);
>> +		btrfs_put_block_group(cache);
>> +		if (ret)
>> +			break;
>> +
>> +		key.offset = found_key.offset + length;
>> +		btrfs_release_path(root, path);
>> +	}
>> +
>> +out:
>> +	btrfs_free_path(path);
>> +	return ret;
>> +}
>> +
>> +static noinline_for_stack int scrub_supers(struct scrub_dev *sdev)
>> +{
>> +	int	i;
>> +	u64	bytenr;
>> +	u64	gen;
>> +	int	ret;
>> +	struct btrfs_device *device = sdev->dev;
>> +	struct btrfs_root *root = device->dev_root;
>> +
>> +	gen = root->fs_info->last_trans_committed;
>> +
>> +	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
>> +		bytenr = btrfs_sb_offset(i);
>> +		if (bytenr + BTRFS_SUPER_INFO_SIZE >= device->total_bytes)
>> +			break;
>> +
>> +		ret = scrub_page(sdev, bytenr, PAGE_SIZE, bytenr, 
>> +		                 BTRFS_EXTENT_FLAG_SUPER, gen, i, NULL, 1);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);
>> +
>> +	return 0;
>> +}
>> +
>> +/*
>> + * get a reference count on fs_info->scrub_workers. start worker if necessary
>> + */
>> +static noinline_for_stack int scrub_workers_get(struct btrfs_root *root)
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	if (fs_info->scrub_workers_refcnt == 0) {
>> +#ifdef SCRUB_BTRFS_WORKER
>> +		btrfs_start_workers(&fs_info->scrub_workers, 1);
>> +#else
>> +		fs_info->scrub_workers = create_workqueue("scrub");
>> +		if (!fs_info->scrub_workers) {
>> +			mutex_unlock(&fs_info->scrub_lock);
>> +			return -ENOMEM;
>> +		}
>> +#endif
>> +	}
>> +	++fs_info->scrub_workers_refcnt;
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +
>> +	return 0;
>> +}
>> +
>> +static noinline_for_stack void scrub_workers_put(struct btrfs_root *root)
> 
> This func is always called immediately after a mutex_unlock(scrub_lock),
> and then takes the lock again. I suggest to drop locking here and adjust
> all callsites.
> 

This does hold only for 2 out of 4 calls. I don't know if it's
worth it, as this is only a very low frequency path.

> Same applies for scrub_workers_get()
> 
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	if (--fs_info->scrub_workers_refcnt == 0) {
>> +#ifdef SCRUB_BTRFS_WORKER
>> +		btrfs_stop_workers(&fs_info->scrub_workers);
>> +#else
>> +		destroy_workqueue(fs_info->scrub_workers);
>> +		fs_info->scrub_workers = NULL;
>> +#endif
>> +
>> +	}
>> +	WARN_ON(fs_info->scrub_workers_refcnt < 0);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +}
>> +
>> +
>> +int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
>> +                    struct btrfs_scrub_progress *progress)
>> +{
>> +	struct scrub_dev *sdev;
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	int ret;
>> +	struct btrfs_device *dev;
>> +
>> +	if (root->fs_info->closing)
>> +		return -EINVAL;
>> +
>> +	/*
>> +	 * check some assumptions
>> +	 */
>> +	if (root->sectorsize != PAGE_SIZE ||
>> +	    root->sectorsize != root->leafsize ||
>> +	    root->sectorsize != root->nodesize) {
>> +		printk(KERN_ERR "btrfs_scrub: size assumptions fail\n");
>> +		return -EINVAL;
>> +	}
>> +	    
>> +	ret = scrub_workers_get(root);
>> +	if (ret)
>> +		return ret;
>> +
>> +	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
>> +	dev = btrfs_find_device(root, devid, NULL, NULL);
>> +	if (!dev || dev->missing) {
>> +		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
>> +		scrub_workers_put(root);
>> +		return -ENODEV;
>> +	}
>> +
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	if (dev->scrub_device) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		scrub_workers_put(root);
>> +		return -EINPROGRESS;
>> +	}
>> +	sdev = scrub_setup_dev(dev);
>> +	if (IS_ERR(sdev)) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		scrub_workers_put(root);
>> +		return PTR_ERR(sdev);
>> +	}
>> +	dev->scrub_device = sdev;
>> +
>> +	atomic_inc(&fs_info->scrubs_running);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
>> +
>> +	down_read(&fs_info->scrub_super_lock);
>> +	ret = scrub_supers(sdev);
>> +	up_read(&fs_info->scrub_super_lock);
>> +
>> +	if (!ret)
>> +		ret = scrub_enumerate_chunks(sdev, start, end);
>> +
>> +	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);
>> +
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	atomic_dec(&fs_info->scrubs_running);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +	wake_up(&fs_info->scrub_pause_wait);
>> +
>> +	if (progress)
>> +		memcpy(progress, &sdev->stat, sizeof(*progress));
>> +
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	dev->scrub_device = NULL;
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +
>> +	scrub_free_dev(sdev);
>> +	scrub_workers_put(root);
>> +
>> +	return ret;
>> +}
>> +
>> +int btrfs_scrub_pause(struct btrfs_root *root)
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	atomic_inc(&fs_info->scrub_pause_req);
>> +	while (atomic_read(&fs_info->scrubs_paused) !=
>> +	       atomic_read(&fs_info->scrubs_running)) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		wait_event(fs_info->scrub_pause_wait,
>> +			   atomic_read(&fs_info->scrubs_paused) ==
>> +			   atomic_read(&fs_info->scrubs_running));
>> +		mutex_lock(&fs_info->scrub_lock);
>> +	}
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +
>> +	return 0;
>> +}
>> +
>> +int btrfs_scrub_continue(struct btrfs_root *root)
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +
>> +	atomic_dec(&fs_info->scrub_pause_req);
>> +	wake_up(&fs_info->scrub_pause_wait);
>> +	return 0;
>> +}
>> +
>> +int btrfs_scrub_pause_super(struct btrfs_root *root)
>> +{
>> +	down_write(&root->fs_info->scrub_super_lock);
>> +	return 0;
>> +}
>> +
>> +int btrfs_scrub_continue_super(struct btrfs_root *root)
>> +{
>> +	up_write(&root->fs_info->scrub_super_lock);
>> +	return 0;
>> +}
>> +
>> +int btrfs_scrub_cancel(struct btrfs_root *root)
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	if (!atomic_read(&fs_info->scrubs_running)) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		return -ENOTCONN;
>> +	}
>> +
>> +	atomic_inc(&fs_info->scrub_cancel_req);
>> +	while(atomic_read(&fs_info->scrubs_running)) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		wait_event(fs_info->scrub_pause_wait,
>> +			   atomic_read(&fs_info->scrubs_running) == 0);
>> +		mutex_lock(&fs_info->scrub_lock);
>> +	}
>> +	atomic_dec(&fs_info->scrub_cancel_req);
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +	
>> +	return 0;
>> +}
>> +
>> +int btrfs_scrub_cancel_dev(struct btrfs_root *root, struct btrfs_device *dev)
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	struct scrub_dev *sdev;
>> +
>> +	mutex_lock(&fs_info->scrub_lock);
>> +	sdev = dev->scrub_device;
>> +	if (!sdev) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		return -ENOTCONN;
>> +	}
>> +	atomic_inc(&sdev->cancel_req);
>> +	while(dev->scrub_device) {
>> +		mutex_unlock(&fs_info->scrub_lock);
>> +		wait_event(fs_info->scrub_pause_wait,
>> +		           dev->scrub_device == NULL);
>> +		mutex_lock(&fs_info->scrub_lock);
>> +	}
>> +	mutex_unlock(&fs_info->scrub_lock);
>> +		
>> +	return 0;
>> +}
>> +int btrfs_scrub_cancel_devid(struct btrfs_root *root, u64 devid)
>> +{
>> +	struct btrfs_fs_info *fs_info = root->fs_info;
>> +	struct btrfs_device *dev;
>> +	int ret;
>> +
>> +	/*
>> +	 * we have to hold the device_list_mutex here so the device
>> +	 * does not go away in cancel_dev. FIXME: find a better solution
>> +	 */
>> +	mutex_lock(&fs_info->fs_devices->device_list_mutex);
>> +	dev = btrfs_find_device(root, devid, NULL, NULL);
>> +	if (!dev) {
>> +		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
>> +		return -ENODEV;
>> +	}
>> +	ret = btrfs_scrub_cancel_dev(root, dev);
>> +	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
>> +
>> +	return ret;
>> +}
>> +	
>> +int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
>> +                         struct btrfs_scrub_progress *progress)
>> +{
>> +	struct btrfs_device *dev;
>> +	struct scrub_dev *sdev = NULL;
>> +
>> +	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
>> +	dev = btrfs_find_device(root, devid, NULL, NULL);
>> +	if (dev)
>> +		sdev = dev->scrub_device;
>> +	if (sdev)
>> +		memcpy(progress, &sdev->stat, sizeof(*progress));
>> +	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
>> +
>> +	return dev ? (sdev ? 0 : -ENOTCONN) : -ENODEV;
>> +}
>> -- 
>> 1.7.3.4
>>
>> --
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