Commit 0ef8e451 authored by Jan Schmidt's avatar Jan Schmidt
Browse files

btrfs scrub: add fixup code for errors on nodatasum files 



This removes a FIXME comment and introduces the first part of nodatasum
fixup: It gets the corresponding inode for a logical address and triggers a
regular readpage for the corrupted sector.

Once we have on-the-fly error correction our error will be automatically
corrected. The correction code is expected to clear the newly introduced
EXTENT_DAMAGED flag, making scrub report that error as "corrected" instead
of "uncorrectable" eventually.

Signed-off-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
parent e12fa9cd

fs/btrfs/extent_io.h

+1 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#define EXTENT_NODATASUM (1 << 10)

#define EXTENT_DO_ACCOUNTING (1 << 11)

#define EXTENT_FIRST_DELALLOC (1 << 12)

#define EXTENT_DAMAGED (1 << 13)

#define EXTENT_IOBITS (EXTENT_LOCKED | EXTENT_WRITEBACK)

#define EXTENT_CTLBITS (EXTENT_DO_ACCOUNTING | EXTENT_FIRST_DELALLOC)

fs/btrfs/scrub.c

+182 −6
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include "volumes.h"

#include "disk-io.h"

#include "ordered-data.h"

#include "transaction.h"

#include "backref.h"



/*
@@ -89,6 +90,7 @@ struct scrub_dev { 
	int			first_free;

	int			curr;

	atomic_t		in_flight;

	atomic_t		fixup_cnt;

	spinlock_t		list_lock;

	wait_queue_head_t	list_wait;

	u16			csum_size;
@@ -102,6 +104,14 @@ struct scrub_dev { 
	spinlock_t		stat_lock;

};



struct scrub_fixup_nodatasum {

	struct scrub_dev	*sdev;

	u64			logical;

	struct btrfs_root	*root;

	struct btrfs_work	work;

	int			mirror_num;

};



struct scrub_warning {

	struct btrfs_path	*path;

	u64			extent_item_size;
@@ -196,6 +206,7 @@ struct scrub_dev *scrub_setup_dev(struct btrfs_device *dev) 
	sdev->first_free = 0;

	sdev->curr = -1;

	atomic_set(&sdev->in_flight, 0);

	atomic_set(&sdev->fixup_cnt, 0);

	atomic_set(&sdev->cancel_req, 0);

	sdev->csum_size = btrfs_super_csum_size(&fs_info->super_copy);

	INIT_LIST_HEAD(&sdev->csum_list);
@@ -347,6 +358,151 @@ out: 
	kfree(swarn.msg_buf);

}



static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *ctx)

{

	struct page *page;

	unsigned long index;

	struct scrub_fixup_nodatasum *fixup = ctx;

	int ret;

	int corrected;

	struct btrfs_key key;

	struct inode *inode;

	u64 end = offset + PAGE_SIZE - 1;

	struct btrfs_root *local_root;



	key.objectid = root;

	key.type = BTRFS_ROOT_ITEM_KEY;

	key.offset = (u64)-1;

	local_root = btrfs_read_fs_root_no_name(fixup->root->fs_info, &key);

	if (IS_ERR(local_root))

		return PTR_ERR(local_root);



	key.type = BTRFS_INODE_ITEM_KEY;

	key.objectid = inum;

	key.offset = 0;

	inode = btrfs_iget(fixup->root->fs_info->sb, &key, local_root, NULL);

	if (IS_ERR(inode))

		return PTR_ERR(inode);



	ret = set_extent_bit(&BTRFS_I(inode)->io_tree, offset, end,

				EXTENT_DAMAGED, 0, NULL, NULL, GFP_NOFS);



	/* set_extent_bit should either succeed or give proper error */

	WARN_ON(ret > 0);

	if (ret)

		return ret < 0 ? ret : -EFAULT;



	index = offset >> PAGE_CACHE_SHIFT;



	page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);

	if (!page)

		return -ENOMEM;



	ret = extent_read_full_page(&BTRFS_I(inode)->io_tree, page,

					btrfs_get_extent, fixup->mirror_num);

	wait_on_page_locked(page);

	corrected = !test_range_bit(&BTRFS_I(inode)->io_tree, offset, end,

					EXTENT_DAMAGED, 0, NULL);



	if (corrected)

		WARN_ON(!PageUptodate(page));

	else

		clear_extent_bit(&BTRFS_I(inode)->io_tree, offset, end,

					EXTENT_DAMAGED, 0, 0, NULL, GFP_NOFS);



	put_page(page);

	iput(inode);



	if (ret < 0)

		return ret;



	if (ret == 0 && corrected) {

		/*

		 * we only need to call readpage for one of the inodes belonging

		 * to this extent. so make iterate_extent_inodes stop

		 */

		return 1;

	}



	return -EIO;

}



static void scrub_fixup_nodatasum(struct btrfs_work *work)

{

	int ret;

	struct scrub_fixup_nodatasum *fixup;

	struct scrub_dev *sdev;

	struct btrfs_trans_handle *trans = NULL;

	struct btrfs_fs_info *fs_info;

	struct btrfs_path *path;

	int uncorrectable = 0;



	fixup = container_of(work, struct scrub_fixup_nodatasum, work);

	sdev = fixup->sdev;

	fs_info = fixup->root->fs_info;



	path = btrfs_alloc_path();

	if (!path) {

		spin_lock(&sdev->stat_lock);

		++sdev->stat.malloc_errors;

		spin_unlock(&sdev->stat_lock);

		uncorrectable = 1;

		goto out;

	}



	trans = btrfs_join_transaction(fixup->root);

	if (IS_ERR(trans)) {

		uncorrectable = 1;

		goto out;

	}



	/*

	 * the idea is to trigger a regular read through the standard path. we

	 * read a page from the (failed) logical address by specifying the

	 * corresponding copynum of the failed sector. thus, that readpage is

	 * expected to fail.

	 * that is the point where on-the-fly error correction will kick in

	 * (once it's finished) and rewrite the failed sector if a good copy

	 * can be found.

	 */

	ret = iterate_inodes_from_logical(fixup->logical, fixup->root->fs_info,

						path, scrub_fixup_readpage,

						fixup);

	if (ret < 0) {

		uncorrectable = 1;

		goto out;

	}

	WARN_ON(ret != 1);



	spin_lock(&sdev->stat_lock);

	++sdev->stat.corrected_errors;

	spin_unlock(&sdev->stat_lock);



out:

	if (trans && !IS_ERR(trans))

		btrfs_end_transaction(trans, fixup->root);

	if (uncorrectable) {

		spin_lock(&sdev->stat_lock);

		++sdev->stat.uncorrectable_errors;

		spin_unlock(&sdev->stat_lock);

		printk_ratelimited(KERN_ERR "btrfs: unable to fixup "

					"(nodatasum) error at logical %llu\n",

					fixup->logical);

	}



	btrfs_free_path(path);

	kfree(fixup);



	/* see caller why we're pretending to be paused in the scrub counters */

	mutex_lock(&fs_info->scrub_lock);

	atomic_dec(&fs_info->scrubs_running);

	atomic_dec(&fs_info->scrubs_paused);

	mutex_unlock(&fs_info->scrub_lock);

	atomic_dec(&sdev->fixup_cnt);

	wake_up(&fs_info->scrub_pause_wait);

	wake_up(&sdev->list_wait);

}



/*

 * 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,
@@ -417,6 +573,7 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix) 
	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 scrub_fixup_nodatasum *fixup;

	u64 logical = sbio->logical + ix * PAGE_SIZE;

	u64 length;

	int i;
@@ -425,12 +582,30 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix) 


	if ((sbio->spag[ix].flags & BTRFS_EXTENT_FLAG_DATA) &&

	    (sbio->spag[ix].have_csum == 0)) {

		fixup = kzalloc(sizeof(*fixup), GFP_NOFS);

		if (!fixup)

			goto uncorrectable;

		fixup->sdev = sdev;

		fixup->logical = logical;

		fixup->root = fs_info->extent_root;

		fixup->mirror_num = sbio->spag[ix].mirror_num;

		/*

		 * nodatasum, don't try to fix anything

		 * FIXME: we can do better, open the inode and trigger a

		 * writeback

		 * increment scrubs_running to prevent cancel requests from

		 * completing as long as a fixup worker is running. we must also

		 * increment scrubs_paused to prevent deadlocking on pause

		 * requests used for transactions commits (as the worker uses a

		 * transaction context). it is safe to regard the fixup worker

		 * as paused for all matters practical. effectively, we only

		 * avoid cancellation requests from completing.

		 */

		goto uncorrectable;

		mutex_lock(&fs_info->scrub_lock);

		atomic_inc(&fs_info->scrubs_running);

		atomic_inc(&fs_info->scrubs_paused);

		mutex_unlock(&fs_info->scrub_lock);

		atomic_inc(&sdev->fixup_cnt);

		fixup->work.func = scrub_fixup_nodatasum;

		btrfs_queue_worker(&fs_info->scrub_workers, &fixup->work);

		return;

	}



	length = PAGE_SIZE;
@@ -1425,10 +1600,11 @@ int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end, 
		ret = scrub_enumerate_chunks(sdev, start, end);



	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);



	atomic_dec(&fs_info->scrubs_running);

	wake_up(&fs_info->scrub_pause_wait);



	wait_event(sdev->list_wait, atomic_read(&sdev->fixup_cnt) == 0);



	if (progress)

		memcpy(progress, &sdev->stat, sizeof(*progress));

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