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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: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
hifive-unleashed-5.1
Filipe Manana 2018-12-07 13:23:32 +00:00 committed by David Sterba
parent 0e94c4f45d
commit 7c3c7cb99c
1 changed files with 14 additions and 20 deletions
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34
fs/btrfs/scrub.c
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@ -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 @@ out:
}
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;