[PATCH stable 6.1] NFS: Fix data corruption caused by congestion.

[PATCH stable 6.1] NFS: Fix data corruption caused by congestion.

[NeilBrown]

when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects
congestion) it is important that the page is redirtied.
nfs_writepage_locked() doesn't do this, so files can become corrupted as
writes can be lost.

Note that this is not needed in v6.8 as AOP_WRITEPAGE_ACTIVATE cannot be
returned.  It is needed for kernels v5.18..v6.7.  From 6.3 onward the patch
is different as it needs to mention "folio", not "page".

Reported-and-tested-by: Jacek Tomaka <Jacek.Tomaka@poczta.fm>
Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfs/write.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index f41d24b54fd1..6a0606668417 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -667,8 +667,10 @@ static int nfs_writepage_locked(struct page *page,
 	int err;
 
 	if (wbc->sync_mode == WB_SYNC_NONE &&
-	    NFS_SERVER(inode)->write_congested)
+	    NFS_SERVER(inode)->write_congested) {
+		redirty_page_for_writepage(wbc, page);
 		return AOP_WRITEPAGE_ACTIVATE;
+	}
 
 	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
 	nfs_pageio_init_write(&pgio, inode, 0,
-- 
2.43.0

Re: [PATCH stable 6.1] NFS: Fix data corruption caused by congestion.

[Greg KH]

On Wed, Feb 28, 2024 at 10:25:49AM +1100, NeilBrown wrote:
> 
> when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects
> congestion) it is important that the page is redirtied.
> nfs_writepage_locked() doesn't do this, so files can become corrupted as
> writes can be lost.
> 
> Note that this is not needed in v6.8 as AOP_WRITEPAGE_ACTIVATE cannot be
> returned.  It is needed for kernels v5.18..v6.7.  From 6.3 onward the patch
> is different as it needs to mention "folio", not "page".
> 
> Reported-and-tested-by: Jacek Tomaka <Jacek.Tomaka@poczta.fm>
> Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  fs/nfs/write.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

All now queued up, thanks.

greg k-h