From 46cc775e29c55d6ae9f4dbb733ec066ff56d3922 Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Mon, 15 Oct 2018 17:04:01 +0300 Subject: [PATCH] btrfs: Adjust loop in free_extent_buffer The loop construct in free_extent_buffer was added in 242e18c7c1a8 ("Btrfs: reduce lock contention on extent buffer locks") as means of reducing the times the eb lock is taken, the non-last ref count is decremented and lock is released. As the special handling of UNMAPPED extent buffers was removed now there is only one decrement op which is happening for EXTENT_BUFFER_UNMAPPED case. This commit modifies the loop condition so that in case of UNMAPPED buffers the eb's lock is taken only if we are 100% sure the eb is going to be freed by the current executor of the code. Additionally, remove superfluous ref count ops in btrfs test. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/extent_io.c | 4 +++- fs/btrfs/tests/btrfs-tests.c | 2 -- fs/btrfs/tests/inode-tests.c | 6 ------ 3 files changed, 3 insertions(+), 9 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 39a41e8..e7cbd3f 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -5074,7 +5074,9 @@ void free_extent_buffer(struct extent_buffer *eb) while (1) { refs = atomic_read(&eb->refs); - if (refs <= 3) + if ((!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs <= 3) + || (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && + refs == 1)) break; old = atomic_cmpxchg(&eb->refs, refs, refs - 1); if (old == refs) diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c index 4cb8fcf..8a59597 100644 --- a/fs/btrfs/tests/btrfs-tests.c +++ b/fs/btrfs/tests/btrfs-tests.c @@ -177,8 +177,6 @@ void btrfs_free_dummy_root(struct btrfs_root *root) if (root->node) { /* One for allocate_extent_buffer */ free_extent_buffer(root->node); - /* One for get_exent_buffer */ - free_extent_buffer(root->node); } kfree(root); } diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c index 64043f0..af0c8e3 100644 --- a/fs/btrfs/tests/inode-tests.c +++ b/fs/btrfs/tests/inode-tests.c @@ -254,11 +254,6 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize) goto out; } - /* - * We will just free a dummy node if it's ref count is 2 so we need an - * extra ref so our searches don't accidentally release our page. - */ - extent_buffer_get(root->node); btrfs_set_header_nritems(root->node, 0); btrfs_set_header_level(root->node, 0); ret = -EINVAL; @@ -860,7 +855,6 @@ static int test_hole_first(u32 sectorsize, u32 nodesize) goto out; } - extent_buffer_get(root->node); btrfs_set_header_nritems(root->node, 0); btrfs_set_header_level(root->node, 0); BTRFS_I(inode)->root = root; -- 2.7.4