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btrfs: add comments to barriers before waitqueue_active

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Reduce number of undocumented barriers out there.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2015-02-16 19:36:47 +01:00
parent 33a9eca7e4
commit a83342aa0c
5 changed files with 16 additions and 2 deletions
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3
fs/btrfs/compression.c
View File

@ -839,6 +839,9 @@ static void free_workspace(int type, struct list_head *workspace)
btrfs_compress_op[idx]->free_workspace(workspace);
atomic_dec(alloc_workspace);
wake:
/*
* Make sure counter is updated before we wake up waiters.
*/
smp_mb();
if (waitqueue_active(workspace_wait))
wake_up(workspace_wait);

3
fs/btrfs/extent-tree.c
View File

@ -10363,8 +10363,7 @@ void btrfs_end_write_no_snapshoting(struct btrfs_root *root)
{
percpu_counter_dec(&root->subv_writers->counter);
/*
* Make sure counter is updated before we wake up
* waiters.
* Make sure counter is updated before we wake up waiters.
*/
smp_mb();
if (waitqueue_active(&root->subv_writers->wait))

3
fs/btrfs/locking.c
View File

@ -280,6 +280,9 @@ void btrfs_tree_unlock(struct extent_buffer *eb)
if (blockers) {
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_dec(&eb->blocking_writers);
/*
* Make sure counter is updated before we wake up waiters.
*/
smp_mb();
if (waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);

6
fs/btrfs/ordered-data.c
View File

@ -345,6 +345,9 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode,
if (entry->bytes_left == 0) {
ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
/*
* Implicit memory barrier after test_and_set_bit
*/
if (waitqueue_active(&entry->wait))
wake_up(&entry->wait);
} else {
@ -409,6 +412,9 @@ int btrfs_dec_test_ordered_pending(struct inode *inode,
if (entry->bytes_left == 0) {
ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
/*
* Implicit memory barrier after test_and_set_bit
*/
if (waitqueue_active(&entry->wait))
wake_up(&entry->wait);
} else {

3
fs/btrfs/transaction.c
View File

@ -861,6 +861,9 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
atomic_dec(&cur_trans->num_writers);
extwriter_counter_dec(cur_trans, trans->type);
/*
* Make sure counter is updated before we wake up waiters.
*/
smp_mb();
if (waitqueue_active(&cur_trans->writer_wait))
wake_up(&cur_trans->writer_wait);