[PATCH 2/2] NFS: Fix a bogus warning in nfs_generic_pgio

[Trond Myklebust]

It is OK for pageused == pagecount in the loop, as long as we don't add
another entry to the *pages array. Move the test so that it only triggers
in that case.

Reported-by: Steve Dickson <SteveD-H+wXaHxf7aLQT0dZR+***@public.gmane.org>
Fixes: bba5c1887a92 (nfs: disallow duplicate pages in pgio page vectors)
Cc: Weston Andros Adamson <dros-7I+n7zu2hftEKMMhf/***@public.gmane.org>
Cc: stable-***@public.gmane.org # 3.16.x
Signed-off-by: Trond Myklebust <trond.myklebust-7I+n7zu2hftEKMMhf/***@public.gmane.org>
---
fs/nfs/pagelist.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 08085de879ed..ed0db61f8543 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -752,12 +752,11 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
nfs_list_remove_request(req);
nfs_list_add_request(req, &hdr->pages);

- if (WARN_ON_ONCE(pageused >= pagecount))
- return nfs_pgio_error(desc, hdr);
-
if (!last_page || last_page != req->wb_page) {
- *pages++ = last_page = req->wb_page;
pageused++;
+ if (pageused > pagecount)
+ break;
+ *pages++ = last_page = req->wb_page;
}
}
if (WARN_ON_ONCE(pageused != pagecount))

[Weston Andros Adamson]

Post by Trond Myklebust
It is OK for pageused == pagecount in the loop, as long as we don't add
another entry to the *pages array. Move the test so that it only triggers
in that case.
Fixes: bba5c1887a92 (nfs: disallow duplicate pages in pgio page vectors)
---
fs/nfs/pagelist.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 08085de879ed..ed0db61f8543 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -752,12 +752,11 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
nfs_list_remove_request(req);
nfs_list_add_request(req, &hdr->pages);
- if (WARN_ON_ONCE(pageused >= pagecount))
- return nfs_pgio_error(desc, hdr);
-
if (!last_page || last_page != req->wb_page) {
- *pages++ = last_page = req->wb_page;
pageused++;
+ if (pageused > pagecount)
+ break;
+ *pages++ = last_page = req->wb_page;

This looks right. Thanks Trond!

-dros

Post by Trond Myklebust
}
}
if (WARN_ON_ONCE(pageused != pagecount))
--
1.9.3

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[Steve Dickson]

Post by Trond Myklebust
It is OK for pageused == pagecount in the loop, as long as we don't add
another entry to the *pages array. Move the test so that it only triggers
in that case.
Fixes: bba5c1887a92 (nfs: disallow duplicate pages in pgio page vectors)

Tested-by: Steve Dickson <steved-H+wXaHxf7aLQT0dZR+***@public.gmane.org>

steved.

Post by Trond Myklebust
---
fs/nfs/pagelist.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 08085de879ed..ed0db61f8543 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -752,12 +752,11 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
nfs_list_remove_request(req);
nfs_list_add_request(req, &hdr->pages);
- if (WARN_ON_ONCE(pageused >= pagecount))
- return nfs_pgio_error(desc, hdr);
-
if (!last_page || last_page != req->wb_page) {
- *pages++ = last_page = req->wb_page;
pageused++;
+ if (pageused > pagecount)
+ break;
+ *pages++ = last_page = req->wb_page;
}
}
if (WARN_ON_ONCE(pageused != pagecount))

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[Steve Dickson]

RIP: 0010:[<ffffffffa053461d>] [<ffffffffa053461d>] __put_nfs_open_context+0x1d/0x100 [nfs]
RSP: 0018:ffff880fed687b90 EFLAGS: 00010286
RAX: 0000000000000024 RBX: 0000000000000000 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff880fed687bc0 R08: 0000000000000092 R09: 000000000000047a
R10: 0000000000000000 R11: ffff880fed6878d6 R12: ffff880fed687d20
R13: ffff880fed687d20 R14: 0000000000000070 R15: ffffea000aa33ec0
FS: 00007fce290f0740(0000) GS:ffff8807ffc60000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000070 CR3: 00000007f2e79000 CR4: 00000000000007e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
0000000000000000 ffff880036c5e510 ffff880fed687d20 ffff880fed687d20
ffff880036c5e200 ffffea000aa33ec0 ffff880fed687bd0 ffffffffa0534710
ffff880fed687be8 ffffffffa053d5f0 ffff880036c5e200 ffff880fed687c08
[<ffffffffa0534710>] put_nfs_open_context+0x10/0x20 [nfs]
[<ffffffffa053d5f0>] nfs_pgio_data_destroy+0x20/0x40 [nfs]
[<ffffffffa053d672>] nfs_pgio_error+0x22/0x40 [nfs]
[<ffffffffa053d8f4>] nfs_generic_pgio+0x74/0x2e0 [nfs]
[<ffffffffa06b18c3>] pnfs_generic_pg_writepages+0x63/0x210 [nfsv4]
[<ffffffffa053d579>] nfs_pageio_doio+0x19/0x50 [nfs]
[<ffffffffa053eb84>] nfs_pageio_complete+0x24/0x30 [nfs]
[<ffffffffa053cb25>] nfs_direct_write_schedule_iovec+0x115/0x1f0 [nfs]
[<ffffffffa053675f>] ? nfs_get_lock_context+0x4f/0x120 [nfs]
[<ffffffffa053d252>] nfs_file_direct_write+0x262/0x420 [nfs]
[<ffffffffa0532d91>] nfs_file_write+0x131/0x1d0 [nfs]
[<ffffffffa0532c60>] ? nfs_need_sync_write.isra.17+0x40/0x40 [nfs]
[<ffffffff812127b8>] do_io_submit+0x3b8/0x840
[<ffffffff81212c50>] SyS_io_submit+0x10/0x20
[<ffffffff81610f29>] system_call_fastpath+0x16/0x1b
This is due to the calls to nfs_pgio_error() in nfs_generic_pgio(), which
happen before the nfs_pgio_header's open context is referenced in
nfs_pgio_rpcsetup().

Tested-by: Steve Dickson <steved-H+wXaHxf7aLQT0dZR+***@public.gmane.org>

steved.

---
fs/nfs/pagelist.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 94e16ec88312..08085de879ed 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -526,7 +526,8 @@ EXPORT_SYMBOL_GPL(nfs_pgio_header_free);
*/
void nfs_pgio_data_destroy(struct nfs_pgio_header *hdr)
{
- put_nfs_open_context(hdr->args.context);
+ if (hdr->args.context)
+ put_nfs_open_context(hdr->args.context);
if (hdr->page_array.pagevec != hdr->page_array.page_array)
kfree(hdr->page_array.pagevec);
}

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