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Commit 7c3c7cb9 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
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Btrfs: scrub, move setup of nofs contexts higher in the stack 



Since scrub workers only do memory allocation with GFP_KERNEL when they
need to perform repair, we can move the recent setup of the nofs context
up to scrub_handle_errored_block() instead of setting it up down the call
chain at insert_full_stripe_lock() and scrub_add_page_to_wr_bio(),
removing some duplicate code and comment. So the only paths for which a
scrub worker can do memory allocations using GFP_KERNEL are the following:

 scrub_bio_end_io_worker()
   scrub_block_complete()
     scrub_handle_errored_block()
       lock_full_stripe()
         insert_full_stripe_lock()
           -> kmalloc with GFP_KERNEL

  scrub_bio_end_io_worker()
    scrub_block_complete()
      scrub_handle_errored_block()
        scrub_write_page_to_dev_replace()
          scrub_add_page_to_wr_bio()
            -> kzalloc with GFP_KERNEL

Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 0e94c4f4

fs/btrfs/scrub.c

+14 −20
Original line number Diff line number Diff line
@@ -322,7 +322,6 @@ static struct full_stripe_lock *insert_full_stripe_lock( 
	struct rb_node *parent = NULL;

	struct full_stripe_lock *entry;

	struct full_stripe_lock *ret;

	unsigned int nofs_flag;



	lockdep_assert_held(&locks_root->lock);
@@ -342,15 +341,8 @@ static struct full_stripe_lock *insert_full_stripe_lock( 


	/*

	 * Insert new lock.

	 *

	 * We must use GFP_NOFS because the scrub task might be waiting for a

	 * worker task executing this function and in turn a transaction commit

	 * might be waiting the scrub task to pause (which needs to wait for all

	 * the worker tasks to complete before pausing).

	 */

	nofs_flag = memalloc_nofs_save();

	ret = kmalloc(sizeof(*ret), GFP_KERNEL);

	memalloc_nofs_restore(nofs_flag);

	if (!ret)

		return ERR_PTR(-ENOMEM);

	ret->logical = fstripe_logical;
@@ -841,6 +833,7 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check) 
	int page_num;

	int success;

	bool full_stripe_locked;

	unsigned int nofs_flag;

	static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,

				      DEFAULT_RATELIMIT_BURST);
@@ -865,6 +858,16 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check) 
	have_csum = sblock_to_check->pagev[0]->have_csum;

	dev = sblock_to_check->pagev[0]->dev;



	/*

	 * We must use GFP_NOFS because the scrub task might be waiting for a

	 * worker task executing this function and in turn a transaction commit

	 * might be waiting the scrub task to pause (which needs to wait for all

	 * the worker tasks to complete before pausing).

	 * We do allocations in the workers through insert_full_stripe_lock()

	 * and scrub_add_page_to_wr_bio(), which happens down the call chain of

	 * this function.

	 */

	nofs_flag = memalloc_nofs_save();

	/*

	 * For RAID5/6, race can happen for a different device scrub thread.

	 * For data corruption, Parity and Data threads will both try
@@ -874,6 +877,7 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check) 
	 */

	ret = lock_full_stripe(fs_info, logical, &full_stripe_locked);

	if (ret < 0) {

		memalloc_nofs_restore(nofs_flag);

		spin_lock(&sctx->stat_lock);

		if (ret == -ENOMEM)

			sctx->stat.malloc_errors++;
@@ -913,7 +917,7 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check) 
	 */



	sblocks_for_recheck = kcalloc(BTRFS_MAX_MIRRORS,

				      sizeof(*sblocks_for_recheck), GFP_NOFS);

				      sizeof(*sblocks_for_recheck), GFP_KERNEL);

	if (!sblocks_for_recheck) {

		spin_lock(&sctx->stat_lock);

		sctx->stat.malloc_errors++;
@@ -1211,6 +1215,7 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check) 
	}



	ret = unlock_full_stripe(fs_info, logical, full_stripe_locked);

	memalloc_nofs_restore(nofs_flag);

	if (ret < 0)

		return ret;

	return 0;
@@ -1629,19 +1634,8 @@ static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx, 
	mutex_lock(&sctx->wr_lock);

again:

	if (!sctx->wr_curr_bio) {

		unsigned int nofs_flag;



		/*

		 * We must use GFP_NOFS because the scrub task might be waiting

		 * for a worker task executing this function and in turn a

		 * transaction commit might be waiting the scrub task to pause

		 * (which needs to wait for all the worker tasks to complete

		 * before pausing).

		 */

		nofs_flag = memalloc_nofs_save();

		sctx->wr_curr_bio = kzalloc(sizeof(*sctx->wr_curr_bio),

					      GFP_KERNEL);

		memalloc_nofs_restore(nofs_flag);

		if (!sctx->wr_curr_bio) {

			mutex_unlock(&sctx->wr_lock);

			return -ENOMEM;