when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects congestion) it is important that the folio 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. Prior to 6.3 the patch is different as it needs to mention "page", not "folio".
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 b664caea8b4e..9e345d3c305a 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -668,8 +668,10 @@ static int nfs_writepage_locked(struct folio *folio, int err;
if (wbc->sync_mode == WB_SYNC_NONE && - NFS_SERVER(inode)->write_congested) + NFS_SERVER(inode)->write_congested) { + folio_redirty_for_writepage(wbc, folio); return AOP_WRITEPAGE_ACTIVATE; + }
nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE); nfs_pageio_init_write(&pgio, inode, 0, false,
On Wed, 2024-02-28 at 10:23 +1100, NeilBrown wrote:
when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects congestion) it is important that the folio 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. Prior to 6.3 the patch is different as it needs to mention "page", not "folio".
Neil, I have a question about the above statement. In Linus's tree as of this morning (v6.8-rc7-ish), it does this in nfs_writepages_locked:
if (wbc->sync_mode == WB_SYNC_NONE && NFS_SERVER(inode)->write_congested) return AOP_WRITEPAGE_ACTIVATE;
The only caller of nfs_writepages_locked, and I don't see where it redirties the page. Why don't we need this in v6.8?
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 b664caea8b4e..9e345d3c305a 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -668,8 +668,10 @@ static int nfs_writepage_locked(struct folio *folio, int err; if (wbc->sync_mode == WB_SYNC_NONE &&
NFS_SERVER(inode)->write_congested)
NFS_SERVER(inode)->write_congested) {folio_redirty_for_writepage(wbc, folio);- }
nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE); nfs_pageio_init_write(&pgio, inode, 0, false,
On Wed, 2024-03-06 at 08:42 -0500, Jeff Layton wrote:
On Wed, 2024-02-28 at 10:23 +1100, NeilBrown wrote:
when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects congestion) it is important that the folio 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. Prior to 6.3 the patch is different as it needs to mention "page", not "folio".
Neil, I have a question about the above statement. In Linus's tree as of this morning (v6.8-rc7-ish), it does this in nfs_writepages_locked:
if (wbc->sync_mode == WB_SYNC_NONE && NFS_SERVER(inode)->write_congested) return AOP_WRITEPAGE_ACTIVATE;
Sorry, I meant to say:
The only caller of nfs_writepages_locked is nfs_wb_folio, and I don't see where it redirties the folio. Why don't we need this in v6.8?
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 b664caea8b4e..9e345d3c305a 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -668,8 +668,10 @@ static int nfs_writepage_locked(struct folio *folio, int err; if (wbc->sync_mode == WB_SYNC_NONE &&
NFS_SERVER(inode)->write_congested)
NFS_SERVER(inode)->write_congested) {folio_redirty_for_writepage(wbc, folio);- }
nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE); nfs_pageio_init_write(&pgio, inode, 0, false,
On Thu, 07 Mar 2024, Jeff Layton wrote:
On Wed, 2024-02-28 at 10:23 +1100, NeilBrown wrote:
when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects congestion) it is important that the folio 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. Prior to 6.3 the patch is different as it needs to mention "page", not "folio".
Neil, I have a question about the above statement. In Linus's tree as of this morning (v6.8-rc7-ish), it does this in nfs_writepages_locked:
if (wbc->sync_mode == WB_SYNC_NONE && NFS_SERVER(inode)->write_congested) return AOP_WRITEPAGE_ACTIVATE;The only caller of nfs_writepages_locked, and I don't see where it redirties the page. Why don't we need this in v6.8?
You are right - it doesn't redirty anything. But there is no bug here.... I didn't see it at first either, but the only caller of nfs_writepage_locked() is nfs_wb_folio() (as you say) and that always passes a wbc with .sync_mode = WB_SYNC_ALL. So sync_mode is never WB_SYNC_NODE and the code snippet you included above is dead code. I've already posted a patch to Trond and Anna to remove that code.
Thanks for the review!
NeilBrown
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 b664caea8b4e..9e345d3c305a 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -668,8 +668,10 @@ static int nfs_writepage_locked(struct folio *folio, int err; if (wbc->sync_mode == WB_SYNC_NONE &&
NFS_SERVER(inode)->write_congested)
NFS_SERVER(inode)->write_congested) {folio_redirty_for_writepage(wbc, folio);- }
nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE); nfs_pageio_init_write(&pgio, inode, 0, false,
-- Jeff Layton jlayton@kernel.org
On Thu, 2024-03-07 at 22:41 +1100, NeilBrown wrote:
On Thu, 07 Mar 2024, Jeff Layton wrote:
On Wed, 2024-02-28 at 10:23 +1100, NeilBrown wrote:
when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects congestion) it is important that the folio 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. Prior to 6.3 the patch is different as it needs to mention "page", not "folio".
Neil, I have a question about the above statement. In Linus's tree as of this morning (v6.8-rc7-ish), it does this in nfs_writepages_locked:
if (wbc->sync_mode == WB_SYNC_NONE && NFS_SERVER(inode)->write_congested) return AOP_WRITEPAGE_ACTIVATE;The only caller of nfs_writepages_locked, and I don't see where it redirties the page. Why don't we need this in v6.8?
You are right - it doesn't redirty anything. But there is no bug here.... I didn't see it at first either, but the only caller of nfs_writepage_locked() is nfs_wb_folio() (as you say) and that always passes a wbc with .sync_mode = WB_SYNC_ALL. So sync_mode is never WB_SYNC_NODE and the code snippet you included above is dead code. I've already posted a patch to Trond and Anna to remove that code.
Thanks for the review!
Thanks Neil,
I missed that bit about the sync_mode. I sent a R-b for your other patch too.
Cheers, Jeff
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 b664caea8b4e..9e345d3c305a 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -668,8 +668,10 @@ static int nfs_writepage_locked(struct folio *folio, int err; if (wbc->sync_mode == WB_SYNC_NONE &&
NFS_SERVER(inode)->write_congested)
NFS_SERVER(inode)->write_congested) {folio_redirty_for_writepage(wbc, folio);- }
nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE); nfs_pageio_init_write(&pgio, inode, 0, false,
-- Jeff Layton jlayton@kernel.org
linux-stable-mirror@lists.linaro.org
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