Re: [PATCH] cifs: fix fallocate when trying to allocate a hole.

[Steve French <smfrench@gmail.com>]

With the minor fix to change the rc from EFBIG to 0 to address the
xfstest 071 failure, tentatively merged into cifs-2.6.git for-next
pending more testing

On Thu, Jul 22, 2021 at 8:21 PM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
>
> Remove the conditional checking for out_data_len and skipping the fallocate
> if it is 0. This is wrong will actually change any legitimate the fallocate
> where the entire region is unallocated into a no-op.
>
> Additionally, before allocating the range, if FALLOC_FL_KEEP_SIZE is set then
> we need to clamp the length of the fallocate region as to not extend the size of the file.
>
> Fixes: 966a3cb7c7db ("cifs: improve fallocate emulation")
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/smb2ops.c | 23 ++++++++++++++++++-----
>  1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index 5cefb5972396..238717654e46 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -3667,11 +3667,6 @@ static int smb3_simple_fallocate_range(unsigned int xid,
>                         (char **)&out_data, &out_data_len);
>         if (rc)
>                 goto out;
> -       /*
> -        * It is already all allocated
> -        */
> -       if (out_data_len == 0)
> -               goto out;
>
>         buf = kzalloc(1024 * 1024, GFP_KERNEL);
>         if (buf == NULL) {
> @@ -3794,6 +3789,24 @@ static long smb3_simple_falloc(struct file *file, struct cifs_tcon *tcon,
>                 goto out;
>         }
>
> +       if (keep_size == true) {
> +               /*
> +                * We can not preallocate pages beyond the end of the file
> +                * in SMB2.
> +                */
> +               if (off >= i_size_read(inode)) {
> +                       rc = -EFBIG;
> +                       goto out;
> +               }
> +               /*
> +                * For fallocates that are partially beyond the end of file,
> +                * clamp len so we only fallocate up to the end of file.
> +                */
> +               if (off + len > i_size_read(inode)) {
> +                       len = i_size_read(inode) - off;
> +               }
> +       }
> +
>         if ((keep_size == true) || (i_size_read(inode) >= off + len)) {
>                 /*
>                  * At this point, we are trying to fallocate an internal
> --
> 2.30.2
>


-- 
Thanks,

Steve