[PATCH v2] nfs: drop the incorrect assertion in nfs_swap_rw()

[PATCH v2] nfs: drop the incorrect assertion in nfs_swap_rw()

[Barry Song]

From: Christoph Hellwig <hch@lst.de>

Since commit 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS
swap-space"), we can plug multiple pages then unplug them all together.
That means iov_iter_count(iter) could be way bigger than PAGE_SIZE, it
actually equals the size of iov_iter_npages(iter, INT_MAX).

Note this issue has nothing to do with large folios as we don't support
THP_SWPOUT to non-block devices.

Fixes: 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space")
Reported-by: Christoph Hellwig <hch@lst.de>
Closes: https://lore.kernel.org/linux-mm/20240617053201.GA16852@lst.de/
Cc: NeilBrown <neilb@suse.de>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Steve French <sfrench@samba.org>
Cc: Trond Myklebust <trondmy@kernel.org>
Cc: Chuanhua Han <hanchuanhua@oppo.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: <stable@vger.kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Martin Wege <martin.l.wege@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
[Barry: figure out the cause and correct the commit message]
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
---
 fs/nfs/direct.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index bb2f583eb28b..90079ca134dd 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -141,8 +141,6 @@ int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter)
 {
 	ssize_t ret;
 
-	VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
-
 	if (iov_iter_rw(iter) == READ)
 		ret = nfs_file_direct_read(iocb, iter, true);
 	else
-- 
2.34.1

Re: [PATCH v2] nfs: drop the incorrect assertion in nfs_swap_rw()

[Martin Wege]

On Tue, Jun 18, 2024 at 8:57 AM Barry Song <21cnbao@gmail.com> wrote:
>
> From: Christoph Hellwig <hch@lst.de>
>
> Since commit 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS
> swap-space"), we can plug multiple pages then unplug them all together.
> That means iov_iter_count(iter) could be way bigger than PAGE_SIZE, it
> actually equals the size of iov_iter_npages(iter, INT_MAX).
>
> Note this issue has nothing to do with large folios as we don't support
> THP_SWPOUT to non-block devices.
>
> Fixes: 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space")
> Reported-by: Christoph Hellwig <hch@lst.de>
> Closes: https://lore.kernel.org/linux-mm/20240617053201.GA16852@lst.de/
> Cc: NeilBrown <neilb@suse.de>
> Cc: Anna Schumaker <anna@kernel.org>
> Cc: Steve French <sfrench@samba.org>
> Cc: Trond Myklebust <trondmy@kernel.org>
> Cc: Chuanhua Han <hanchuanhua@oppo.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Chris Li <chrisl@kernel.org>
> Cc: "Huang, Ying" <ying.huang@intel.com>
> Cc: Jeff Layton <jlayton@kernel.org>
> Cc: <stable@vger.kernel.org>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Martin Wege <martin.l.wege@gmail.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> [Barry: figure out the cause and correct the commit message]
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> ---
>  fs/nfs/direct.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index bb2f583eb28b..90079ca134dd 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c

Please add a

Reviewed-by: Martin Wege <martin.l.wege@gmail.com>

Thanks,
Martin

Re: [PATCH v2] nfs: drop the incorrect assertion in nfs_swap_rw()

[Christoph Hellwig]

On Tue, Jun 18, 2024 at 06:56:47PM +1200, Barry Song wrote:
> Fixes: 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space")
> Reported-by: Christoph Hellwig <hch@lst.de>

> Signed-off-by: Christoph Hellwig <hch@lst.de>

A reported-by for the credited patch author doesn't make sense.

Re: [PATCH v2] nfs: drop the incorrect assertion in nfs_swap_rw()

[Barry Song]

On Wed, Jun 19, 2024 at 5:27 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Tue, Jun 18, 2024 at 06:56:47PM +1200, Barry Song wrote:
> > Fixes: 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space")
> > Reported-by: Christoph Hellwig <hch@lst.de>
>
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> A reported-by for the credited patch author doesn't make sense.

Andrew, could you help remove the "reported-by" in the commit log?
Alternatively, would you prefer that I send a v3 to drop the "reported-by"?

>

Re: [PATCH v2] nfs: drop the incorrect assertion in nfs_swap_rw()

[Andrew Morton]

On Wed, 19 Jun 2024 17:34:27 +1200 Barry Song <21cnbao@gmail.com> wrote:

> On Wed, Jun 19, 2024 at 5:27 PM Christoph Hellwig <hch@lst.de> wrote:
> >
> > On Tue, Jun 18, 2024 at 06:56:47PM +1200, Barry Song wrote:
> > > Fixes: 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space")
> > > Reported-by: Christoph Hellwig <hch@lst.de>
> >
> > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> >
> > A reported-by for the credited patch author doesn't make sense.
> 
> Andrew, could you help remove the "reported-by" in the commit log?
> Alternatively, would you prefer that I send a v3 to drop the "reported-by"?

I made that edit.