[PATCH 04/11] nfs: combine NFS_LAYOUT_RETURN and NFS_LAYOUT_RETURN_LOCK

[NeilBrown <neilb@suse.de>]

The flags NFS_LAYOUT_RETURN and NFS_LAYOUT_RETURN_LOCK are effectively
identical.
The only time either are cleared is in pnfs_clear_layoutreturn_waitbit(),
and there both are cleared.
The only time NFS_LAYOUT_RETURN is set is in pnfs_prepare_layoutreturn()
immediately after NFS_LAYOUT_RETURN_LOCK was set.
The only other time that NFS_LAYOUT_RETURN_LOCK is set is in
pnfs_mark_layout_stateid_invalid() if NFS_LAYOUT_RETURN was set but
NFS_LAYOUT_RETURN_LOCK was not set - but that is an impossible
combination given that else where the flags are set or cleared together.

So we only need one of these flags.  This patch discards
NFS_LAYOUT_RETURN_LOCK and does the test_and_set needed for exclusion with
NFS_LAYOUT_RETURN.

Also the wake_up_bit in pnfs_clear_layoutreturn_waitbit() is changed to
clear_and_wake_up_bit() which includes all needed barriers internally.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfs/pnfs.c | 15 ++++-----------
 fs/nfs/pnfs.h |  1 -
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 0d16b383a452..5963c0440e23 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -386,10 +386,7 @@ pnfs_clear_layoutreturn_info(struct pnfs_layout_hdr *lo)
 
 static void pnfs_clear_layoutreturn_waitbit(struct pnfs_layout_hdr *lo)
 {
-	clear_bit_unlock(NFS_LAYOUT_RETURN, &lo->plh_flags);
-	clear_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags);
-	smp_mb__after_atomic();
-	wake_up_bit(&lo->plh_flags, NFS_LAYOUT_RETURN);
+	clear_and_wake_up_bit(NFS_LAYOUT_RETURN, &lo->plh_flags);
 	rpc_wake_up(&NFS_SERVER(lo->plh_inode)->roc_rpcwaitq);
 }
 
@@ -471,9 +468,6 @@ pnfs_mark_layout_stateid_invalid(struct pnfs_layout_hdr *lo,
 	pnfs_clear_layoutreturn_info(lo);
 	pnfs_free_returned_lsegs(lo, lseg_list, &range, 0);
 	set_bit(NFS_LAYOUT_DRAIN, &lo->plh_flags);
-	if (test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags) &&
-	    !test_and_set_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags))
-		pnfs_clear_layoutreturn_waitbit(lo);
 	return !list_empty(&lo->plh_segs);
 }
 
@@ -1310,9 +1304,8 @@ pnfs_prepare_layoutreturn(struct pnfs_layout_hdr *lo,
 	/* Serialise LAYOUTGET/LAYOUTRETURN */
 	if (atomic_read(&lo->plh_outstanding) != 0)
 		return false;
-	if (test_and_set_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags))
+	if (test_and_set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags))
 		return false;
-	set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags);
 	pnfs_get_layout_hdr(lo);
 	nfs4_stateid_copy(stateid, &lo->plh_stateid);
 	*cred = get_cred(lo->plh_lc_cred);
@@ -1454,7 +1447,7 @@ _pnfs_return_layout(struct inode *ino)
 	/* Reference matched in nfs4_layoutreturn_release */
 	pnfs_get_layout_hdr(lo);
 	/* Is there an outstanding layoutreturn ? */
-	if (test_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags)) {
+	if (test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) {
 		spin_unlock(&ino->i_lock);
 		if (wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN,
 					TASK_UNINTERRUPTIBLE))
@@ -1564,7 +1557,7 @@ bool pnfs_roc(struct inode *ino,
 		goto out_noroc;
 	}
 	pnfs_get_layout_hdr(lo);
-	if (test_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags)) {
+	if (test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) {
 		spin_unlock(&ino->i_lock);
 		rcu_read_unlock();
 		wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN,
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 30d2613e912b..df914f17b927 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -100,7 +100,6 @@ enum {
 	NFS_LAYOUT_RW_FAILED,		/* get rw layout failed stop trying */
 	NFS_LAYOUT_BULK_RECALL,		/* bulk recall affecting layout */
 	NFS_LAYOUT_RETURN,		/* layoutreturn in progress */
-	NFS_LAYOUT_RETURN_LOCK,		/* Serialise layoutreturn */
 	NFS_LAYOUT_RETURN_REQUESTED,	/* Return this layout ASAP */
 	NFS_LAYOUT_INVALID_STID,	/* layout stateid id is invalid */
 	NFS_LAYOUT_FIRST_LAYOUTGET,	/* Serialize first layoutget */
-- 
2.47.0