linux-kernel - [PATCH 1/2] BKL: Remove BKL from default

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Message-Id: <1258560457-15129-1-git-send-email-jblunck@suse.de>
Date:	Wed, 18 Nov 2009 17:07:36 +0100
From:	Jan Blunck <jblunck@...e.de>
To:	linux-fsdevel@...r.kernel.org
Cc:	Linux-Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, jkacur@...hat.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Jan Blunck <jblunck@...e.de>, Arnd Bergmann <arnd@...db.de>,
	Christoph Hellwig <hch@...radead.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 1/2] BKL: Remove BKL from default_llseek()

Using the BKL in llseek() does not protect the inode's i_size from
modification since the i_size is protected by a seqlock nowadays. Since
default_llseek() is already using the i_size_read() wrapper it is not the
BKL which is serializing the access here.
The access to file->f_pos is not protected by the BKL either since its
access in vfs_write()/vfs_read() is not protected by any lock. If the BKL
is not protecting anything here it can clearly get removed.

Signed-off-by: Jan Blunck <jblunck@...e.de>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Frédéric Weisbecker <fweisbec@...il.com>
Cc: John Kacur <jkacur@...hat.com>
---
 fs/read_write.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 3ac2898..0e491cc 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -107,7 +107,6 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
 {
 	loff_t retval;
 
-	lock_kernel();
 	switch (origin) {
 		case SEEK_END:
 			offset += i_size_read(file->f_path.dentry->d_inode);
@@ -128,7 +127,6 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
 		retval = offset;
 	}
 out:
-	unlock_kernel();
 	return retval;
 }
 EXPORT_SYMBOL(default_llseek);
-- 
1.6.4.2

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