2024-02-27 23:30:51

by NeilBrown

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

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 <[email protected]>
Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
Signed-off-by: NeilBrown <[email protected]>
---
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

2024-03-04 11:31:58

by Greg KH

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

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 <[email protected]>
> Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
> Signed-off-by: NeilBrown <[email protected]>
> ---
> fs/nfs/write.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)

All now queued up, thanks.

greg k-h