Re: [PATCH v2 2/5] btrfs: split btrfs_insert_delayed_dir_index() into prealloc and commit phases

[Qu Wenruo]

在 2026/8/5 01:14, Jeff Layton 写道:
> Split btrfs_insert_delayed_dir_index() into three functions using a new
> btrfs_dir_index_prealloc struct to bundle the pre-allocated resources:
>
> - btrfs_prealloc_delayed_dir_index(): performs the two GFP_NOFS
>    allocations (delayed node + delayed item) that can fail with -ENOMEM.
> - btrfs_insert_delayed_dir_index_prealloc(): populates the item data,
>    inserts into the rb-tree, and reserves metadata space. Cannot fail
>    with -ENOMEM since all allocations were done in the prealloc step.
> - btrfs_free_delayed_dir_index_prealloc(): frees pre-allocated
>    resources when the caller's btree insertion fails.
>
> The original btrfs_insert_delayed_dir_index() is refactored into a thin
> wrapper that calls the prealloc and commit functions.
>
> This split allows callers to move the fallible memory allocations before
> the point of no return (the DIR_ITEM btree insertion), so that -ENOMEM
> can be returned cleanly without aborting the transaction.
>
> Assisted-by: LLM
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
>   fs/btrfs/delayed-inode.c | 111 +++++++++++++++++++++++++++++++++++++----------
>   fs/btrfs/delayed-inode.h |  17 ++++++++
>   2 files changed, 104 insertions(+), 24 deletions(-)
>
> diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
> index db2ffab0941a..95d2dca80444 100644
> --- a/fs/btrfs/delayed-inode.c
> +++ b/fs/btrfs/delayed-inode.c
> @@ -6,6 +6,7 @@
>   
>   #include <linux/slab.h>
>   #include <linux/iversion.h>
> +#include <linux/error-injection.h>
>   #include "ctree.h"
>   #include "fs.h"
>   #include "messages.h"
> @@ -1469,35 +1470,74 @@ static void btrfs_release_dir_index_item_space(struct btrfs_trans_handle *trans)
>   	trans->bytes_reserved -= bytes;
>   }
>   
> -/* Will return 0, -ENOMEM or -EEXIST (index number collision, unexpected). */
> -int btrfs_insert_delayed_dir_index(struct btrfs_trans_handle *trans,
> -				   const char *name, int name_len,
> -				   struct btrfs_inode *dir,
> -				   const struct btrfs_disk_key *disk_key, u8 flags,
> -				   u64 index)
> +/*
> + * Pre-allocate a delayed node and delayed item for a dir index insertion.
> + * Call this before modifying the btree so that ENOMEM can be returned
> + * before any on-disk state has changed.
> + *
> + * Returns 0 on success, -ENOMEM on allocation failure.
> + */
> +int btrfs_prealloc_delayed_dir_index(struct btrfs_inode *dir,
> +				     const char *name, int name_len,
> +				     struct btrfs_dir_index_prealloc *prealloc)

We can directly return a btrfs_dir_index_prealloc pointer, which reduce 
the parameter list.

Otherwise looks good to me.

Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>

Thanks,
Qu