https://github.com/torvalds/linux
Revision 914ee295af418e936ec20a08c1663eaabe4cd07a authored by Xin Zhong on 09 December 2010, 09:30:14 UTC, committed by Chris Mason on 10 December 2010, 21:29:10 UTC
This problem is found in meego testing: http://bugs.meego.com/show_bug.cgi?id=6672 A file in btrfs is mmaped and the mmaped buffer is passed to pwrite to write to the same page of the same file. In btrfs_file_aio_write(), the pages is locked by prepare_pages(). So when btrfs_copy_from_user() is called, page fault happens and the same page needs to be locked again in filemap_fault(). The fix is to move iov_iter_fault_in_readable() before prepage_pages() to make page fault happen before pages are locked. And also disable page fault in critical region in btrfs_copy_from_user(). Reviewed-by: Yan, Zheng<zheng.z.yan@intel.com> Signed-off-by: Zhong, Xin <xin.zhong@intel.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
1 parent f106e82
Tip revision: 914ee295af418e936ec20a08c1663eaabe4cd07a authored by Xin Zhong on 09 December 2010, 09:30:14 UTC
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
Tip revision: 914ee29
jfs_debug.c
/*
* Copyright (C) International Business Machines Corp., 2000-2004
* Portions Copyright (C) Christoph Hellwig, 2001-2002
*
* This program 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; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/fs.h>
#include <linux/ctype.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/uaccess.h>
#include "jfs_incore.h"
#include "jfs_filsys.h"
#include "jfs_debug.h"
#ifdef PROC_FS_JFS /* see jfs_debug.h */
static struct proc_dir_entry *base;
#ifdef CONFIG_JFS_DEBUG
static int jfs_loglevel_proc_show(struct seq_file *m, void *v)
{
seq_printf(m, "%d\n", jfsloglevel);
return 0;
}
static int jfs_loglevel_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, jfs_loglevel_proc_show, NULL);
}
static ssize_t jfs_loglevel_proc_write(struct file *file,
const char __user *buffer, size_t count, loff_t *ppos)
{
char c;
if (get_user(c, buffer))
return -EFAULT;
/* yes, I know this is an ASCIIism. --hch */
if (c < '0' || c > '9')
return -EINVAL;
jfsloglevel = c - '0';
return count;
}
static const struct file_operations jfs_loglevel_proc_fops = {
.owner = THIS_MODULE,
.open = jfs_loglevel_proc_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
.write = jfs_loglevel_proc_write,
};
#endif
static struct {
const char *name;
const struct file_operations *proc_fops;
} Entries[] = {
#ifdef CONFIG_JFS_STATISTICS
{ "lmstats", &jfs_lmstats_proc_fops, },
{ "txstats", &jfs_txstats_proc_fops, },
{ "xtstat", &jfs_xtstat_proc_fops, },
{ "mpstat", &jfs_mpstat_proc_fops, },
#endif
#ifdef CONFIG_JFS_DEBUG
{ "TxAnchor", &jfs_txanchor_proc_fops, },
{ "loglevel", &jfs_loglevel_proc_fops }
#endif
};
#define NPROCENT ARRAY_SIZE(Entries)
void jfs_proc_init(void)
{
int i;
if (!(base = proc_mkdir("fs/jfs", NULL)))
return;
for (i = 0; i < NPROCENT; i++)
proc_create(Entries[i].name, 0, base, Entries[i].proc_fops);
}
void jfs_proc_clean(void)
{
int i;
if (base) {
for (i = 0; i < NPROCENT; i++)
remove_proc_entry(Entries[i].name, base);
remove_proc_entry("fs/jfs", NULL);
}
}
#endif /* PROC_FS_JFS */
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