[PATCH] [RFC] Fix deadlock on regular nonseekable files

From: Vitaly Chernooky <vitalii.chernookyi@globallogic.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David Vrabel" <david.vrabel@citrix.com>,
	"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
	"Iurii Konovalenko" <iurii.konovalenko@globallogic.com>,
	"Ian Campbell" <ian.campbell@citrix.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Andrii Anisov" <andrii.anisov@globallogic.com>,
	"Artem Mygaiev" <artem.mygaiev@globallogic.com>
Subject: [PATCH] [RFC] Fix deadlock on regular nonseekable files
Date: Fri, 20 Mar 2015 15:17:54 +0200	[thread overview]
Message-ID: <CANZZXhCCUh12_1gt0ppc4cMMR-BUsq4rySqNihsEJziOGYbh3A@mail.gmail.com> (raw)

>From 8ef72cde695d1b1a3e9f6165477c9e7415fca2b1 Mon Sep 17 00:00:00 2001
From: Vitaly Chernooky <vitaly.chernooky@globallogic.com>
Date: Fri, 20 Mar 2015 12:26:37 +0200
Subject: [PATCH] Fix deadlock on regular nonseekable files

'Commit 9c225f2655e36a470c4f58dbbc99244c5fc7f2d4 ("vfs: atomic f_pos
accesses as per POSIX")' introduce following regression. If some program
does multithreaded IO on file in pseudo-filesystem, like procfs, with
nonseekable files marked as regular, we get deadlock on f_pos_lock
mutex, if there are simultaneous reading and writing by different
threads.

Signed-off-by: Vitaly Chernooky <vitaly.chernooky@globallogic.com>
---
 fs/open.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/open.c b/fs/open.c
index 33f9cbf..1a4f84b 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1135,7 +1135,7 @@ EXPORT_SYMBOL(generic_file_open);
  */
 int nonseekable_open(struct inode *inode, struct file *filp)
 {
- filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
+ filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE |
FMODE_ATOMIC_POS);
  return 0;
 }

-- 
1.7.9.5

With best regards,

-- 
Vitaly Chernooky | Senior Developer - Product Engineering and Development
GlobalLogic
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