| Message ID | 22af99f197c4926165d4f556546379a81ae8a44f.1694174371.git.fdmanana@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: updates to delayed refs accounting and space reservation | expand |
On Fri, Sep 08, 2023 at 01:09:04PM +0100, fdmanana@kernel.org wrote: > From: Filipe Manana <fdmanana@suse.com> > > When starting a transaction, with a non-zero number of items, we reserve > metadata space for that number of items and for delayed refs by doing a > call to btrfs_block_rsv_add(), with the transaction block reserve passed > as the block reserve argument. This reserves metadata space and adds it > to the transaction block reserve. Later we migrate the space we reserved > for delayed references from the transaction block reserve into the delayed > refs block reserve, by calling btrfs_migrate_to_delayed_refs_rsv(). > > btrfs_migrate_to_delayed_refs_rsv() decrements the number of bytes to > migrate from the source block reserve, and this however may result in an > underflow in case the space added to the transaction block reserve ended > up being used by another task that has not reserved enough space for its > own use - examples are tasks doing reflinks or hole punching because they > end up calling btrfs_replace_file_extents() -> btrfs_drop_extents() and > may need to modify/COW a variable number of leaves/paths, so they keep > trying to use space from the transaction block reserve when they need to > COW an extent buffer, and may end up trying to use more space then they > have reserved (1 unit/path only for removing file extent items). > > This can be avoided by simply reserving space first without adding it to > the transaction block reserve, then add the space for delayed refs to the > delayed refs block reserve and finally add the remaining reserved space > to the transaction block reserve. This also makes the code a bit shorter > and simpler. So just do that. > > Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Thanks, Josef
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c index 1043f66cc130..9fe4ccca50a0 100644 --- a/fs/btrfs/delayed-ref.c +++ b/fs/btrfs/delayed-ref.c @@ -103,24 +103,17 @@ void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans) * Transfer bytes to our delayed refs rsv. * * @fs_info: the filesystem - * @src: source block rsv to transfer from * @num_bytes: number of bytes to transfer * - * This transfers up to the num_bytes amount from the src rsv to the + * This transfers up to the num_bytes amount, previously reserved, to the * delayed_refs_rsv. Any extra bytes are returned to the space info. */ void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info, - struct btrfs_block_rsv *src, u64 num_bytes) { struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv; u64 to_free = 0; - spin_lock(&src->lock); - src->reserved -= num_bytes; - src->size -= num_bytes; - spin_unlock(&src->lock); - spin_lock(&delayed_refs_rsv->lock); if (delayed_refs_rsv->size > delayed_refs_rsv->reserved) { u64 delta = delayed_refs_rsv->size - diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h index b8e14b0ba5f1..fd9bf2b709c0 100644 --- a/fs/btrfs/delayed-ref.h +++ b/fs/btrfs/delayed-ref.h @@ -407,7 +407,6 @@ void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans); int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info, enum btrfs_reserve_flush_enum flush); void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info, - struct btrfs_block_rsv *src, u64 num_bytes); bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info); diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index ab09542f2170..1985ab543ad2 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -625,14 +625,15 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, reloc_reserved = true; } - ret = btrfs_block_rsv_add(fs_info, rsv, num_bytes, flush); + ret = btrfs_reserve_metadata_bytes(fs_info, rsv, num_bytes, flush); if (ret) goto reserve_fail; if (delayed_refs_bytes) { - btrfs_migrate_to_delayed_refs_rsv(fs_info, rsv, + btrfs_migrate_to_delayed_refs_rsv(fs_info, delayed_refs_bytes); num_bytes -= delayed_refs_bytes; } + btrfs_block_rsv_add_bytes(rsv, num_bytes, true); if (rsv->space_info->force_alloc) do_chunk_alloc = true;