[PATCH AUTOSEL 4.9 08/34] nfs: don't dirty kernel pages read by direct-io

Sasha Levin
2018-12-13T04:32:19Z

From: Dave Kleikamp <dave.kleikamp@oracle.com>

[ Upstream commit ad3cba223ac02dc769c3bbe88efe277bbb457566 ]

When we use direct_IO with an NFS backing store, we can trigger a
WARNING in __set_page_dirty(), as below, since we're dirtying the page
unnecessarily in nfs_direct_read_completion().

To fix, replicate the logic in commit 53cbf3b157a0 ("fs: direct-io:
don't dirtying pages for ITER_BVEC/ITER_KVEC direct read").

Other filesystems that implement direct_IO handle this; most use
blockdev_direct_IO(). ceph and cifs have similar logic.

mount 127.0.0.1:/export /nfs
dd if=/dev/zero of=/nfs/image bs=1M count=200
losetup --direct-io=on -f /nfs/image
mkfs.btrfs /dev/loop0
mount -t btrfs /dev/loop0 /mnt/

kernel: WARNING: CPU: 0 PID: 8067 at fs/buffer.c:580 __set_page_dirty+0xaf/0xd0
kernel: Modules linked in: loop(E) nfsv3(E) rpcsec_gss_krb5(E) nfsv4(E) dns_resolver(E) nfs(E) fscache(E) nfsd(E) auth_rpcgss(E) nfs_acl(E) lockd(E) grace(E) fuse(E) tun(E) ip6t_rpfilter(E) ipt_REJECT(E) nf_
kernel: snd_seq(E) snd_seq_device(E) snd_pcm(E) video(E) snd_timer(E) snd(E) soundcore(E) ip_tables(E) xfs(E) libcrc32c(E) sd_mod(E) sr_mod(E) cdrom(E) ata_generic(E) pata_acpi(E) crc32c_intel(E) ahci(E) li
kernel: CPU: 0 PID: 8067 Comm: kworker/0:2 Tainted: G E 4.20.0-rc1.master.20181111.ol7.x86_64 #1
kernel: Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
kernel: Workqueue: nfsiod rpc_async_release [sunrpc]
kernel: RIP: 0010:__set_page_dirty+0xaf/0xd0
kernel: Code: c3 48 8b 02 f6 c4 04 74 d4 48 89 df e8 ba 05 f7 ff 48 89 c6 eb cb 48 8b 43 08 a8 01 75 1f 48 89 d8 48 8b 00 a8 04 74 02 eb 87 <0f> 0b eb 83 48 83 e8 01 eb 9f 48 83 ea 01 0f 1f 00 eb 8b 48 83 e8
kernel: RSP: 0000:ffffc1c8825b7d78 EFLAGS: 00013046
kernel: RAX: 000fffffc0020089 RBX: fffff2b603308b80 RCX: 0000000000000001
kernel: RDX: 0000000000000001 RSI: ffff9d11478115c8 RDI: ffff9d11478115d0
kernel: RBP: ffffc1c8825b7da0 R08: 0000646f6973666e R09: 8080808080808080
kernel: R10: 0000000000000001 R11: 0000000000000000 R12: ffff9d11478115d0
kernel: R13: ffff9d11478115c8 R14: 0000000000003246 R15: 0000000000000001
kernel: FS: 0000000000000000(0000) GS:ffff9d115ba00000(0000) knlGS:0000000000000000
kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 00007f408686f640 CR3: 0000000104d8e004 CR4: 00000000000606f0
kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
kernel: Call Trace:
kernel: __set_page_dirty_buffers+0xb6/0x110
kernel: set_page_dirty+0x52/0xb0
kernel: nfs_direct_read_completion+0xc4/0x120 [nfs]
kernel: nfs_pgio_release+0x10/0x20 [nfs]
kernel: rpc_free_task+0x30/0x70 [sunrpc]
kernel: rpc_async_release+0x12/0x20 [sunrpc]
kernel: process_one_work+0x174/0x390
kernel: worker_thread+0x4f/0x3e0
kernel: kthread+0x102/0x140
kernel: ? drain_workqueue+0x130/0x130
kernel: ? kthread_stop+0x110/0x110
kernel: ret_from_fork+0x35/0x40
kernel: ---[ end trace 01341980905412c9 ]---

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

[forward-ported to v4.20]
Signed-off-by: Calum Mackay <calum.mackay@oracle.com>
Reviewed-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/direct.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 1ab91124a93e..53f0012ace42 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -98,8 +98,11 @@ struct nfs_direct_req {
struct pnfs_ds_commit_info ds_cinfo; /* Storage for cinfo */
struct work_struct work;
int flags;
+ /* for write */
#define NFS_ODIRECT_DO_COMMIT (1) /* an unstable reply was received */
#define NFS_ODIRECT_RESCHED_WRITES (2) /* write verification failed */
+ /* for read */
+#define NFS_ODIRECT_SHOULD_DIRTY (3) /* dirty user-space page after read */
struct nfs_writeverf verf; /* unstable write verifier */
};

@@ -422,7 +425,8 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
struct nfs_page *req = nfs_list_entry(hdr->pages.next);
struct page *page = req->wb_page;

- if (!PageCompound(page) && bytes < hdr->good_bytes)
+ if (!PageCompound(page) && bytes < hdr->good_bytes &&
+ (dreq->flags == NFS_ODIRECT_SHOULD_DIRTY))
set_page_dirty(page);
bytes += req->wb_bytes;
nfs_list_remove_request(req);
@@ -597,6 +601,9 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;

+ if (iter_is_iovec(iter))
+ dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
+
nfs_start_io_direct(inode);

NFS_I(inode)->read_io += count;
--
2.19.1