[PATCH 7/8] lockd: don't attempt blocking locks on nfs reexports

J. Bruce Fields
2021-08-20T21:02:18Z

From: "J. Bruce Fields" <bfields@redhat.com>

As in the v4 case, it doesn't work well to block waiting for a lock on
an nfs filesystem.

As in the v4 case, that means we're depending on the client to poll.
It's probably incorrect to depend on that, but I *think* clients do poll
in practice. In any case, it's an improvement over hanging the lockd
thread indefinitely as we currently are.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
fs/lockd/svclock.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index d60e6eea2d57..c99acefb9ec9 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -31,6 +31,7 @@
#include <linux/lockd/nlm.h>
#include <linux/lockd/lockd.h>
#include <linux/kthread.h>
+#include <linux/exportfs.h>

#define NLMDBG_FACILITY NLMDBG_SVCLOCK

@@ -470,18 +471,24 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
struct nlm_cookie *cookie, int reclaim)
{
struct nlm_block *block = NULL;
+ struct inode *inode = nlmsvc_file_inode(file);
int error;
int mode;
+ int async_block = 0;
__be32 ret;

dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
- nlmsvc_file_inode(file)->i_sb->s_id,
- nlmsvc_file_inode(file)->i_ino,
+ inode->i_sb->s_id, inode->i_ino,
lock->fl.fl_type, lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end,
wait);

+ if (inode->i_sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS) {
+ async_block = wait;
+ wait = 0;
+ }
+
/* Lock file against concurrent access */
mutex_lock(&file->f_mutex);
/* Get existing block (in case client is busy-waiting)
@@ -542,7 +549,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
*/
if (wait)
break;
- ret = nlm_lck_denied;
+ ret = async_block ? nlm_lck_blocked : nlm_lck_denied;
goto out;
case FILE_LOCK_DEFERRED:
if (wait)
--
2.31.1