Re: [PATCH 1/3] ntfs: set the attribute list size before reserving space for it

[liubaolin]

在 2026/9/27 18:57, Matthias Goergens 写道:
> ntfs_attrlist_update_locked() resizes the attribute list and then, for
> $MFT, tries to reserve the maximum list size.  When that allocation
> fails with -ENOSPC it falls back to ntfs_attrlist_repack(), which reads
> the list through ntfs_inode_attr_pread().  The read stops at i_size,
> but i_size is only updated after the reserve, so when the list has just
> grown the repack gets a short read and returns -EIO.  Only -ENOSPC from
> the reserve is ignored, so the -EIO fails the $MFT extension and with
> it the file creation that needed a new mft record.
>
> On a 32 MiB volume with 512-byte clusters whose $MFT has a non-resident
> attribute list, 591 of 1500 creations of empty files succeed and the
> rest fail with EIO while 742 KiB is still free:
>
>    ntfs: (device vda): ntfs_attrlist_update_locked(): Failed to reserve attribute list space
>    ntfs: Failed add attr entry to attrlist
>    ntfs: MP update failed
>    ntfs: (device vda): ntfs_mft_record_alloc(): Failed to extend mft data allocation.
>
> Update i_size as soon as the list has been resized.  File creation then
> goes on until the volume is full and fails with ENOSPC.
>
> Fixes: b1d732e62a5b ("ntfs: repack $MFT/$ATTRIBUTE LIST")
> Signed-off-by: Matthias Goergens <matthias.goergens@xxxxxxxxx>
> ---
> The volume is frag.img from
> https://github.com/matthiasgoergens/linux/tree/reproducer/2026-09-26-ntfs-mft-runlist
> (mft-bootstrap/frag.img.xz); creating empty files on it until one fails
> is enough.  Tested with KASAN and lockdep: after the patch the files
> written before the volume filled read back intact after a remount, and
> ntfsfix and ntfsresize --info find nothing wrong with the image.
> ---
>   fs/ntfs/attrlist.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ntfs/attrlist.c b/fs/ntfs/attrlist.c
> index 1bbd2bc62c582..62dfb96e31a3c 100644
> --- a/fs/ntfs/attrlist.c
> +++ b/fs/ntfs/attrlist.c
> @@ -252,6 +252,9 @@ int ntfs_attrlist_update_locked(struct ntfs_inode *base_ni,
>   		return err;
>   	}
>   
> +	/* ntfs_attrlist_repack() below reads the list up to i_size. */
> +	i_size_write(attr_vi, base_ni->attr_list_size);
> +
>   	/*
>   	 * Reserve the maximum legal list size while the MFT metadata area is
>   	 * still easy to allocate contiguously. This prevents a later list entry
> @@ -279,8 +282,6 @@ int ntfs_attrlist_update_locked(struct ntfs_inode *base_ni,
>   		}
>   	}
>   
> -	i_size_write(attr_vi, base_ni->attr_list_size);
> -
>   	if (NInoNonResident(attr_ni) && !NInoAttrListNonResident(base_ni))
>   		NInoSetAttrListNonResident(base_ni);
>   

Looks good to me.

Reviewed-by: Baolin Liu <liubaolin@xxxxxxxxxx>