linux-kernel - [PATCH 49/58] staging: lustre: llite: avoid a deadlock in page write

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Message-Id: <1469155491-15265-50-git-send-email-jsimmons@infradead.org>
Date:	Thu, 21 Jul 2016 22:44:42 -0400
From:	James Simmons <jsimmons@...radead.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devel@...verdev.osuosl.org,
	Andreas Dilger <andreas.dilger@...el.com>,
	Oleg Drokin <oleg.drokin@...el.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lustre Development List <lustre-devel@...ts.lustre.org>,
	Jinshan Xiong <jinshan.xiong@...el.com>,
	James Simmons <jsimmons@...radead.org>
Subject: [PATCH 49/58] staging: lustre: llite: avoid a deadlock in page write

From: Jinshan Xiong <jinshan.xiong@...el.com>

For a partial page write, it will have to issue a READ RPC firstly
to get a full uptodate page. If another page is already locked by
this thread it can easily cause deadlock.

Signed-off-by: Jinshan Xiong <jinshan.xiong@...el.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4873
Reviewed-on: http://review.whamcloud.com/9928
Reviewed-by: Bobi Jam <bobijam@...il.com>
Reviewed-by: Niu Yawei <yawei.niu@...el.com>
Reviewed-by: Oleg Drokin <oleg.drokin@...el.com>
Signed-off-by: James Simmons <jsimmons@...radead.org>
---
 drivers/staging/lustre/lustre/llite/rw26.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/rw26.c b/drivers/staging/lustre/lustre/llite/rw26.c
index d98c7ac..c14a1b6 100644
--- a/drivers/staging/lustre/lustre/llite/rw26.c
+++ b/drivers/staging/lustre/lustre/llite/rw26.c
@@ -506,8 +506,9 @@ static int ll_write_begin(struct file *file, struct address_space *mapping,
 	env = lcc->lcc_env;
 	io  = lcc->lcc_io;
 
-	/* To avoid deadlock, try to lock page first. */
-	vmpage = grab_cache_page_nowait(mapping, index);
+	if (likely(to == PAGE_SIZE)) /* LU-4873 */
+		/* To avoid deadlock, try to lock page first. */
+		vmpage = grab_cache_page_nowait(mapping, index);
 	if (unlikely(!vmpage || PageDirty(vmpage) || PageWriteback(vmpage))) {
 		struct vvp_io *vio = vvp_env_io(env);
 		struct cl_page_list *plist = &vio->u.write.vui_queue;
-- 
1.7.1