Btrfs: barrier before waitqueue_active
We need a barrir before calling waitqueue_active otherwise we will miss
wakeups. So in places that do atomic_dec(); then atomic_read() use
atomic_dec_return() which imply a memory barrier (see memory-barriers.txt)
and then add an explicit memory barrier everywhere else that need them.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 86eff48..43d1c5a 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -818,6 +818,7 @@
btrfs_compress_op[idx]->free_workspace(workspace);
atomic_dec(alloc_workspace);
wake:
+ smp_mb();
if (waitqueue_active(workspace_wait))
wake_up(workspace_wait);
}
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 00deed4e..07d5eeb 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -512,8 +512,8 @@
rb_erase(&delayed_item->rb_node, root);
delayed_item->delayed_node->count--;
- atomic_dec(&delayed_root->items);
- if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND &&
+ if (atomic_dec_return(&delayed_root->items) <
+ BTRFS_DELAYED_BACKGROUND &&
waitqueue_active(&delayed_root->wait))
wake_up(&delayed_root->wait);
}
@@ -1056,8 +1056,7 @@
delayed_node->count--;
delayed_root = delayed_node->root->fs_info->delayed_root;
- atomic_dec(&delayed_root->items);
- if (atomic_read(&delayed_root->items) <
+ if (atomic_dec_return(&delayed_root->items) <
BTRFS_DELAYED_BACKGROUND &&
waitqueue_active(&delayed_root->wait))
wake_up(&delayed_root->wait);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a7ad8fc..dd86a5d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -754,9 +754,7 @@
limit = btrfs_async_submit_limit(fs_info);
limit = limit * 2 / 3;
- atomic_dec(&fs_info->nr_async_submits);
-
- if (atomic_read(&fs_info->nr_async_submits) < limit &&
+ if (atomic_dec_return(&fs_info->nr_async_submits) < limit &&
waitqueue_active(&fs_info->async_submit_wait))
wake_up(&fs_info->async_submit_wait);
@@ -3783,14 +3781,17 @@
/* FIXME: cleanup wait for commit */
t->in_commit = 1;
t->blocked = 1;
+ smp_mb();
if (waitqueue_active(&root->fs_info->transaction_blocked_wait))
wake_up(&root->fs_info->transaction_blocked_wait);
t->blocked = 0;
+ smp_mb();
if (waitqueue_active(&root->fs_info->transaction_wait))
wake_up(&root->fs_info->transaction_wait);
t->commit_done = 1;
+ smp_mb();
if (waitqueue_active(&t->commit_wait))
wake_up(&t->commit_wait);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2d65c52..97baf00 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1007,9 +1007,7 @@
nr_pages = (async_cow->end - async_cow->start + PAGE_CACHE_SIZE) >>
PAGE_CACHE_SHIFT;
- atomic_sub(nr_pages, &root->fs_info->async_delalloc_pages);
-
- if (atomic_read(&root->fs_info->async_delalloc_pages) <
+ if (atomic_sub_return(nr_pages, &root->fs_info->async_delalloc_pages) <
5 * 1024 * 1024 &&
waitqueue_active(&root->fs_info->async_submit_wait))
wake_up(&root->fs_info->async_submit_wait);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3b39450..0b1e69d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -227,9 +227,8 @@
cur = pending;
pending = pending->bi_next;
cur->bi_next = NULL;
- atomic_dec(&fs_info->nr_async_bios);
- if (atomic_read(&fs_info->nr_async_bios) < limit &&
+ if (atomic_dec_return(&fs_info->nr_async_bios) < limit &&
waitqueue_active(&fs_info->async_submit_wait))
wake_up(&fs_info->async_submit_wait);