Re: [PATCH v3 0/6] btrfs: handle -ENOMEM errors in some synchronous dirops without aborting

[Qu Wenruo <wqu@suse.com>]

在 2026/8/12 03:44, Jeff Layton 写道:
> This version fixes some issues Qu pointed out in review of v2. I did end
> up adopting his suggestion to allocate the prealloc container as well,
> which makes the API cleaner. Original cover letter follows:
> 
> We've had a (relatively small) number of ENOMEM btrfs aborts occur in
> synchronous directory morphing codepaths. It's not terribly common, but
> there are a few places where an memory allocation failure results in an
> abort.
> 
> This patchset reworks the code to do the allocations up front, before the
> point where we'd have to abort the fs if it fails.
> 
> This does not cover all potential cases where this can currently occur:
> 
> In particular, a rename that overwrites the target can still abort the
> fs if a memory allocation fails. Fixing that is substantially more work,
> unfortunately.
> 
> This also doesn't cover orphaning a new inode on failure (which can
> trigger new memory allocations), so this series is designed to work in
> conjunction with with Boris' GFP_NOFAIL series [1].
> 
> AFAICT, these are ancient problems, dating back at least to ~2011. I
> didn't bother adding Fixes: tags.
> 
> AI disclosure: I made heavy use of an LLM in this patchset, from
> drafting the initial series to helping test it.
> 
> [1] https://lore.kernel.org/linux-btrfs/cover.1784673567.git.boris@bur.io/
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
> Changes in v3:
> - btrfs_prealloc_delayed_dir_index() now allocates and returns the
>    btrfs_dir_index_prealloc instead of filling in a caller-provided on-stack
>    struct, so a NULL pointer means "no prealloc" and callers no longer need
>    to use prealloc->item as an is-allocated flag (as suggested by Qu).
> - Fix a leak of a caller-supplied prealloc in btrfs_insert_dir_item() when
>    btrfs_alloc_path() fails; all error exits now go through a single
>    out_free_prealloc label (Qu Wenruo).
> - Move the dir index name memcpy into btrfs_prealloc_delayed_dir_index()
>    instead of duplicating it at the call sites (Qu Wenruo).
> - New patch to use an on-stack path in btrfs_del_orphan_item().
> - btrfs_create_new_inode(): persist nlink=0 with btrfs_update_inode() after
>    orphaning the new inode. Otherwise orphan cleanup sees nlink > 0, drops
>    the orphan item and leaks the inode.
> - Pick up Reviewed-by tags from Qu Wenruo.
> - Link to v2: https://lore.kernel.org/r/20260804-btrfs-enomem-v2-0-4d923170e8c1@kernel.org
> 
> Changes in v2:
> - Use an on-stack btrfs_path in btrfs_insert_orphan_item() so the ENOMEM
>    recovery does not itself fail on a path allocation.
> - Simplify the recovery in btrfs_create_new_inode() to rely on
>    btrfs_orphan_add()'s internal abort instead of aborting twice.
> - Add ALLOW_ERROR_INJECTION() on btrfs_prealloc_delayed_dir_index() and a
>    new fstest (btrfs/351) to exercise the ENOMEM path.
> - Link to v1: https://lore.kernel.org/r/20260717-btrfs-enomem-v1-0-cdc9c0e265d0@kernel.org
> 
> ---
> Jeff Layton (6):
>        btrfs: use an on-stack path in btrfs_insert_orphan_item()
>        btrfs: use an on-stack path in btrfs_del_orphan_item()
>        btrfs: split btrfs_insert_delayed_dir_index() into prealloc and commit phases
>        btrfs: pre-allocate delayed dir index before btree modification
>        btrfs: handle ENOMEM from btrfs_insert_dir_item() without aborting
>        btrfs: pre-allocate delayed dir index for non-overwrite rename
> 
>   fs/btrfs/btrfs_inode.h   |   4 +-
>   fs/btrfs/delayed-inode.c | 115 ++++++++++++++++++++++++++++++++++++-----------
>   fs/btrfs/delayed-inode.h |  22 ++++++---
>   fs/btrfs/dir-item.c      |  42 +++++++++++------
>   fs/btrfs/dir-item.h      |   5 ++-
>   fs/btrfs/inode.c         |  64 +++++++++++++++++++++-----
>   fs/btrfs/orphan.c        |  36 +++++++--------
>   fs/btrfs/transaction.c   |   2 +-
>   fs/btrfs/tree-log.c      |   4 +-
>   9 files changed, 215 insertions(+), 79 deletions(-)
> ---
> base-commit: 76d8783d4c196f4ac990b97ee9f56d2e6797e173
> change-id: 20260715-btrfs-enomem-988f2cc36ffd
> 
> Best regards,