[PATCH 3.4 092/214] NFSv4.1: Fix a race in pNFS layoutcommit

Greg Kroah-Hartman
2014-06-05T04:21:03Z

From: Trond Myklebust <Trond.Myklebust@netapp.com>

commit a073dbff359f4741013ae4b8395f5364c5e00b48 upstream.

We need to clear the NFS_LSEG_LAYOUTCOMMIT bits atomically with the
NFS_INO_LAYOUTCOMMIT bit, otherwise we may end up with situations
where the two are out of sync.
The first half of the problem is to ensure that pnfs_layoutcommit_inode
clears the NFS_LSEG_LAYOUTCOMMIT bit through pnfs_list_write_lseg.
We still need to keep the reference to those segments until the RPC call
is finished, so in order to make it clear _where_ those references come
from, we add a helper pnfs_list_write_lseg_done() that cleans up after
pnfs_list_write_lseg.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Benny Halevy <bhalevy@tonian.com>
[bwh: Backported to 3.2: s/pnfs_put_lseg/put_lseg/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/nfs4proc.c | 14 --------------
fs/nfs/pnfs.c | 19 ++++++++++++++++++-
2 files changed, 18 insertions(+), 15 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6297,22 +6297,8 @@ nfs4_layoutcommit_done(struct rpc_task *
static void nfs4_layoutcommit_release(void *calldata)
{
struct nfs4_layoutcommit_data *data = calldata;
- struct pnfs_layout_segment *lseg, *tmp;
- unsigned long *bitlock = &NFS_I(data->args.inode)->flags;

pnfs_cleanup_layoutcommit(data);
- /* Matched by references in pnfs_set_layoutcommit */
- list_for_each_entry_safe(lseg, tmp, &data->lseg_list, pls_lc_list) {
- list_del_init(&lseg->pls_lc_list);
- if (test_and_clear_bit(NFS_LSEG_LAYOUTCOMMIT,
- &lseg->pls_flags))
- put_lseg(lseg);
- }
-
- clear_bit_unlock(NFS_INO_LAYOUTCOMMITTING, bitlock);
- smp_mb__after_clear_bit();
- wake_up_bit(bitlock, NFS_INO_LAYOUTCOMMITTING);
-
put_rpccred(data->cred);
kfree(data);
}
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1381,11 +1381,27 @@ static void pnfs_list_write_lseg(struct

list_for_each_entry(lseg, &NFS_I(inode)->layout->plh_segs, pls_list) {
if (lseg->pls_range.iomode == IOMODE_RW &&
- test_bit(NFS_LSEG_LAYOUTCOMMIT, &lseg->pls_flags))
+ test_and_clear_bit(NFS_LSEG_LAYOUTCOMMIT, &lseg->pls_flags))
list_add(&lseg->pls_lc_list, listp);
}
}

+static void pnfs_list_write_lseg_done(struct inode *inode, struct list_head *listp)
+{
+ struct pnfs_layout_segment *lseg, *tmp;
+ unsigned long *bitlock = &NFS_I(inode)->flags;
+
+ /* Matched by references in pnfs_set_layoutcommit */
+ list_for_each_entry_safe(lseg, tmp, listp, pls_lc_list) {
+ list_del_init(&lseg->pls_lc_list);
+ put_lseg(lseg);
+ }
+
+ clear_bit_unlock(NFS_INO_LAYOUTCOMMITTING, bitlock);
+ smp_mb__after_clear_bit();
+ wake_up_bit(bitlock, NFS_INO_LAYOUTCOMMITTING);
+}
+
void pnfs_set_lo_fail(struct pnfs_layout_segment *lseg)
{
if (lseg->pls_range.iomode == IOMODE_RW) {
@@ -1434,6 +1450,7 @@ void pnfs_cleanup_layoutcommit(struct nf

if (nfss->pnfs_curr_ld->cleanup_layoutcommit)
nfss->pnfs_curr_ld->cleanup_layoutcommit(data);
+ pnfs_list_write_lseg_done(data->args.inode, &data->lseg_list);
}

/*