android_kernel_samsung_msm8976/fs/exofs/file.c
Nick Piggin 97178b7b6c exofs: simple fsync race fix
It is incorrect to test inode dirty bits without participating in the inode
writeback protocol. Inode writeback sets I_SYNC and clears I_DIRTY_?, then
writes out the particular bits, then clears I_SYNC when it is done. BTW. it
may not completely write all pages out, so I_DIRTY_PAGES would get set
again.

This is a standard pattern used throughout the kernel's writeback caches
(I_SYNC ~= I_WRITEBACK, if that makes it clearer).

And so it is not possible to determine an inode's dirty status just by
checking I_DIRTY bits. Especially not for the purpose of data integrity
syncs.

Missing the check for these bits means that fsync can complete while
writeback to the inode is underway. Inode writeback functions get this
right, so call into them rather than try to shortcut things by testing
dirty state improperly.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
2011-03-15 15:02:50 +02:00

87 lines
2.5 KiB
C

/*
* Copyright (C) 2005, 2006
* Avishay Traeger (avishay@gmail.com)
* Copyright (C) 2008, 2009
* Boaz Harrosh <bharrosh@panasas.com>
*
* Copyrights for code taken from ext2:
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card (card@masi.ibp.fr)
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
* from
* linux/fs/minix/inode.c
* Copyright (C) 1991, 1992 Linus Torvalds
*
* This file is part of exofs.
*
* exofs is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation. Since it is based on ext2, and the only
* valid version of GPL for the Linux kernel is version 2, the only valid
* version of GPL for exofs is version 2.
*
* exofs is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with exofs; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "exofs.h"
static int exofs_release_file(struct inode *inode, struct file *filp)
{
return 0;
}
/* exofs_file_fsync - flush the inode to disk
*
* Note, in exofs all metadata is written as part of inode, regardless.
* The writeout is synchronous
*/
static int exofs_file_fsync(struct file *filp, int datasync)
{
int ret;
struct inode *inode = filp->f_mapping->host;
struct super_block *sb;
ret = sync_inode_metadata(inode, 1);
/* This is a good place to write the sb */
/* TODO: Sechedule an sb-sync on create */
sb = inode->i_sb;
if (sb->s_dirt)
exofs_sync_fs(sb, 1);
return ret;
}
static int exofs_flush(struct file *file, fl_owner_t id)
{
int ret = vfs_fsync(file, 0);
/* TODO: Flush the OSD target */
return ret;
}
const struct file_operations exofs_file_operations = {
.llseek = generic_file_llseek,
.read = do_sync_read,
.write = do_sync_write,
.aio_read = generic_file_aio_read,
.aio_write = generic_file_aio_write,
.mmap = generic_file_mmap,
.open = generic_file_open,
.release = exofs_release_file,
.fsync = exofs_file_fsync,
.flush = exofs_flush,
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
};
const struct inode_operations exofs_file_inode_operations = {
.setattr = exofs_setattr,
};