linux-kernel - [PATCH v2 1/2] netfs: do not unlock and put the folio twice

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Message-Id: <20220705025255.331695-2-xiubli@redhat.com>
Date:   Tue,  5 Jul 2022 10:52:54 +0800
From:   xiubli@...hat.com
To:     dhowells@...hat.com
Cc:     linux-kernel@...r.kernel.org, willy@...radead.org,
        keescook@...omium.org, linux-fsdevel@...r.kernel.org,
        linux-cachefs@...hat.com, ceph-devel@...r.kernel.org,
        marc.dionne@...istor.com, linux-afs@...ts.infradead.org,
        Xiubo Li <xiubli@...hat.com>
Subject: [PATCH v2 1/2] netfs: do not unlock and put the folio twice

From: Xiubo Li <xiubli@...hat.com>

check_write_begin() will unlock and put the folio when return
non-zero. So we should avoid unlocking and putting it twice in
netfs layer.

URL: https://tracker.ceph.com/issues/56423
Signed-off-by: Xiubo Li <xiubli@...hat.com>
---
 fs/netfs/buffered_read.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 42f892c5712e..b6fd6e5fe019 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -320,7 +320,7 @@ static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
  * pointer to the fsdata cookie that gets returned to the VM to be passed to
  * write_end.  It is permitted to sleep.  It should return 0 if the request
  * should go ahead; unlock the folio and return -EAGAIN to cause the folio to
- * be regot; or return an error.
+ * be regot; or unlock the folio and return an error.
  *
  * The calling netfs must initialise a netfs context contiguous to the vfs
  * inode before calling this.
@@ -353,7 +353,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
 			trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
 			if (ret == -EAGAIN)
 				goto retry;
-			goto error;
+			goto error_unlocked;
 		}
 	}
 
@@ -375,7 +375,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
 				   NETFS_READ_FOR_WRITE);
 	if (IS_ERR(rreq)) {
 		ret = PTR_ERR(rreq);
-		goto error;
+		goto error_locked;
 	}
 	rreq->no_unlock_folio	= folio_index(folio);
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
@@ -402,12 +402,12 @@ int netfs_write_begin(struct netfs_inode *ctx,
 
 	ret = netfs_begin_read(rreq, true);
 	if (ret < 0)
-		goto error;
+		goto error_locked;
 
 have_folio:
 	ret = folio_wait_fscache_killable(folio);
 	if (ret < 0)
-		goto error;
+		goto error_locked;
 have_folio_no_wait:
 	*_folio = folio;
 	_leave(" = 0");
@@ -415,9 +415,10 @@ int netfs_write_begin(struct netfs_inode *ctx,
 
 error_put:
 	netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
-error:
+error_locked:
 	folio_unlock(folio);
 	folio_put(folio);
+error_unlocked:
 	_leave(" = %d", ret);
 	return ret;
 }
-- 
2.36.0.rc1