linux-kernel - [PATCH] [RFC] Fix deadlock on regular nonseekable files

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

>From 8ef72cde695d1b1a3e9f6165477c9e7415fca2b1 Mon Sep 17 00:00:00 2001
From: Vitaly Chernooky <vitaly.chernooky@...ballogic.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@...ballogic.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
P +380.44.4929695 ext.1136 M +380.63.6011802 S cvv_2k
www.globallogic.com

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