On 05/21, Wenjie Qi wrote:
> F2FS large folio support is read-only. It rejects writable opens and
> mmap writes when an inode mapping supports large folios, but setattr can
> still reach the inode without going through those checks.
>
> For immutable large-folio files, clearing the immutable flag keeps the
> cached inode and its large-folio mapping alive until the inode is
> dropped. A path-based truncate(2) can then call f2fs_setattr() with
> ATTR_SIZE and change the file size without opening the file for write.
>
> The user.fadvise path adds another visible case: after the file is
> reopened with large folios, chmod(WRITE) is documented to fail, but
> f2fs_setattr() currently allows ATTR_MODE to add write bits back.
We don't add this anymore. Can you update?
>
> Reject size changes and mode changes that enable write permissions while
> the mapping still supports large folios. Read-only mode changes and
> unrelated metadata updates remain allowed.
>
> Fixes: 05e65c14ea59 ("f2fs: support large folio for immutable non-compressed
> case")
> Signed-off-by: Wenjie Qi <[email protected]>
> ---
> fs/f2fs/file.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 71385ca4163d..3880ff5e6740 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1097,6 +1097,11 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct
> dentry *dentry,
> ATTR_GID | ATTR_TIMES_SET))))
> return -EPERM;
>
> + if (mapping_large_folio_support(inode->i_mapping) &&
> + ((attr->ia_valid & ATTR_SIZE) ||
> + ((attr->ia_valid & ATTR_MODE) && (attr->ia_mode & 0222))))
> + return -EOPNOTSUPP;
> +
> if ((attr->ia_valid & ATTR_SIZE)) {
> if (!f2fs_is_compress_backend_ready(inode) ||
> IS_DEVICE_ALIASING(inode))
> --
> 2.43.0
>
>
>
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