[PATCH] fuse: remove page alignment check for writeback len

[PATCH] fuse: remove page alignment check for writeback len

[Joanne Koong]

Remove incorrect page alignment check for the writeback len arg in
fuse_iomap_writeback_range(). len will always be block-aligned as passed
in by iomap. On regular fuse filesystems, i_blkbits is set to PAGE_SHIFT
so this is not a problem but for fuseblk filesystems, the block size is
set to a default of 512 bytes or a block size passed in at mount time.

Please note that non-page-aligned lens are fine for the logic in
fuse_iomap_writeback_range(). The check was originally added as a
safeguard to detect conspicuously wrong ranges.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Fixes: ef7e7cbb323f ("fuse: use iomap for writeback")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

[1] report:
https://lore.kernel.org/linux-fsdevel/CA+G9fYs5AdVM-T2Tf3LciNCwLZEHetcnSkHsjZajVwwpM2HmJw@mail.gmail.com/
---
 fs/fuse/file.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index f16426fd2bf5..883dc94a0ce0 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2155,8 +2155,6 @@ static ssize_t fuse_iomap_writeback_range(struct iomap_writepage_ctx *wpc,
 	loff_t offset = offset_in_folio(folio, pos);
 
 	WARN_ON_ONCE(!data);
-	/* len will always be page aligned */
-	WARN_ON_ONCE(len & (PAGE_SIZE - 1));
 
 	if (!data->ff) {
 		data->ff = fuse_write_file_get(fi);
-- 
2.47.3

Re: [PATCH] fuse: remove page alignment check for writeback len

[Darrick J. Wong]

On Wed, Jul 23, 2025 at 04:08:50PM -0700, Joanne Koong wrote:
> Remove incorrect page alignment check for the writeback len arg in
> fuse_iomap_writeback_range(). len will always be block-aligned as passed
> in by iomap. On regular fuse filesystems, i_blkbits is set to PAGE_SHIFT
> so this is not a problem but for fuseblk filesystems, the block size is
> set to a default of 512 bytes or a block size passed in at mount time.
> 
> Please note that non-page-aligned lens are fine for the logic in
> fuse_iomap_writeback_range(). The check was originally added as a
> safeguard to detect conspicuously wrong ranges.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> Fixes: ef7e7cbb323f ("fuse: use iomap for writeback")
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

Seems fine to me,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> 
> [1] report:
> https://lore.kernel.org/linux-fsdevel/CA+G9fYs5AdVM-T2Tf3LciNCwLZEHetcnSkHsjZajVwwpM2HmJw@mail.gmail.com/
> ---
>  fs/fuse/file.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index f16426fd2bf5..883dc94a0ce0 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2155,8 +2155,6 @@ static ssize_t fuse_iomap_writeback_range(struct iomap_writepage_ctx *wpc,
>  	loff_t offset = offset_in_folio(folio, pos);
>  
>  	WARN_ON_ONCE(!data);
> -	/* len will always be page aligned */
> -	WARN_ON_ONCE(len & (PAGE_SIZE - 1));
>  
>  	if (!data->ff) {
>  		data->ff = fuse_write_file_get(fi);
> -- 
> 2.47.3
> 
> 

Re: [PATCH] fuse: remove page alignment check for writeback len

[Naresh Kamboju]

On Thu, 24 Jul 2025 at 21:55, Darrick J. Wong <djwong@kernel.org> wrote:
>
> On Wed, Jul 23, 2025 at 04:08:50PM -0700, Joanne Koong wrote:
> > Remove incorrect page alignment check for the writeback len arg in
> > fuse_iomap_writeback_range(). len will always be block-aligned as passed
> > in by iomap. On regular fuse filesystems, i_blkbits is set to PAGE_SHIFT
> > so this is not a problem but for fuseblk filesystems, the block size is
> > set to a default of 512 bytes or a block size passed in at mount time.
> >
> > Please note that non-page-aligned lens are fine for the logic in
> > fuse_iomap_writeback_range(). The check was originally added as a
> > safeguard to detect conspicuously wrong ranges.
> >
> > Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> > Fixes: ef7e7cbb323f ("fuse: use iomap for writeback")
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

I have applied this patch on top of the Linux next tree and performed
testing. The previously reported regressions [1] are no longer observed.
Thank you for providing the fix.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>

>
> Seems fine to me,
> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
>
> --D
>
> >

[1] report:
https://lore.kernel.org/linux-fsdevel/CA+G9fYs5AdVM-T2Tf3LciNCwLZEHetcnSkHsjZajVwwpM2HmJw@mail.gmail.com/

> > ---
> >  fs/fuse/file.c | 2 --
> >  1 file changed, 2 deletions(-)
> >
> > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > index f16426fd2bf5..883dc94a0ce0 100644
> > --- a/fs/fuse/file.c
> > +++ b/fs/fuse/file.c
> > @@ -2155,8 +2155,6 @@ static ssize_t fuse_iomap_writeback_range(struct iomap_writepage_ctx *wpc,
> >       loff_t offset = offset_in_folio(folio, pos);
> >
> >       WARN_ON_ONCE(!data);
> > -     /* len will always be page aligned */
> > -     WARN_ON_ONCE(len & (PAGE_SIZE - 1));
> >
> >       if (!data->ff) {
> >               data->ff = fuse_write_file_get(fi);
> > --
> > 2.47.3
> >
> >


--
Linaro LKFT
https://lkft.linaro.org