[2/9] btrfs: avoid extra memory allocation when copying free space cache

Commit Message

Filipe Manana May 4, 2023, 11:04 a.m. UTC

From: Filipe Manana <[e-mail]>

At copy_free_space_cache(), we add a new entry to the block group's ctl
before we free the entry from the temporary ctl. Adding a new entry
requires the allocation of a new struct btrfs_free_space, so we can
avoid a temporary extra allocation by freeing the entry from the
temporary ctl before we add a new entry to the main ctl, which possibly
also reduces the chances for a memory allocation failure in case of very
high memory pressure. So just do that.

Signed-off-by: Filipe Manana <[e-mail]>
---
 fs/btrfs/free-space-cache.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Anand Jain May 5, 2023, 8:27 a.m. UTC | #1

LGTM

Reviewed-by: Anand Jain <[e-mail]>

Patch

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index cf98a3c05480..ec53119d4cfb 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -923,10 +923,12 @@  static int copy_free_space_cache(struct btrfs_block_group *block_group,
 	while (!ret && (n = rb_first(&ctl->free_space_offset)) != NULL) {
 		info = rb_entry(n, struct btrfs_free_space, offset_index);
 		if (!info->bitmap) {
+			const u64 offset = info->offset;
+			const u64 bytes = info->bytes;
+
 			unlink_free_space(ctl, info, true);
-			ret = btrfs_add_free_space(block_group, info->offset,
-						   info->bytes);
 			kmem_cache_free(btrfs_free_space_cachep, info);
+			ret = btrfs_add_free_space(block_group, offset, bytes);
 		} else {
 			u64 offset = info->offset;
 			u64 bytes = ctl->unit;