Re: [PATCH 10/10] fs: replace mmap hook with .mmap_prepare for simple mappings

On Mon, Jun 16, 2025 at 08:33:29PM +0100, Lorenzo Stoakes wrote:
> Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> callback"), the f_op->mmap() hook has been deprecated in favour of
> f_op->mmap_prepare().
> 
> This callback is invoked in the mmap() logic far earlier, so error handling
> can be performed more safely without complicated and bug-prone state
> unwinding required should an error arise.
> 
> This hook also avoids passing a pointer to a not-yet-correctly-established
> VMA avoiding any issues with referencing this data structure.
> 
> It rather provides a pointer to the new struct vm_area_desc descriptor type
> which contains all required state and allows easy setting of required
> parameters without any consideration needing to be paid to locking or
> reference counts.
> 
> Note that nested filesystems like overlayfs are compatible with an
> .mmap_prepare() callback since commit bb666b7c2707 ("mm: add mmap_prepare()
> compatibility layer for nested file systems").
> 
> In this patch we apply this change to file systems with relatively simple
> mmap() hook logic - exfat, ceph, f2fs, bcachefs, zonefs, btrfs, ocfs2,
> orangefs, nilfs2, romfs, ramfs and aio.
> 
> Signed-off-by: Lorenzo Stoakes <[email protected]>
> ---

For

>  fs/btrfs/file.c       |  7 ++++---

Acked-by: David Sterba <[email protected]>

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