Revision 03cdadb04077b9311bbc67d98cc5401aff76482d authored by Dan Williams on 26 February 2016, 23:19:43 UTC, committed by Linus Torvalds on 27 February 2016, 18:28:52 UTC
The recent *sync enabling discovered that we are inserting into the
block_device pagecache counter to the expectations of the dirty data
tracking for dax mappings.  This can lead to data corruption.

We want to support DAX for block devices eventually, but it requires
wider changes to properly manage the pagecache.

   dump_stack+0x85/0xc2
   dax_writeback_mapping_range+0x60/0xe0
   blkdev_writepages+0x3f/0x50
   do_writepages+0x21/0x30
   __filemap_fdatawrite_range+0xc6/0x100
   filemap_write_and_wait+0x4a/0xa0
   set_blocksize+0x70/0xd0
   sb_set_blocksize+0x1d/0x50
   ext4_fill_super+0x75b/0x3360
   mount_bdev+0x180/0x1b0
   ext4_mount+0x15/0x20
   mount_fs+0x38/0x170

Mark the support broken so its disabled by default, but otherwise still
available for testing.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@fb.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent a4a8481
Raw File
clz_ctz.c
/*
 * lib/clz_ctz.c
 *
 * Copyright (C) 2013 Chanho Min <chanho.min@lge.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 * The functions in this file aren't called directly, but are required by
 * GCC builtins such as __builtin_ctz, and therefore they can't be removed
 * despite appearing unreferenced in kernel source.
 *
 * __c[lt]z[sd]i2 can be overridden by linking arch-specific versions.
 */

#include <linux/export.h>
#include <linux/kernel.h>

int __weak __ctzsi2(int val);
int __weak __ctzsi2(int val)
{
	return __ffs(val);
}
EXPORT_SYMBOL(__ctzsi2);

int __weak __clzsi2(int val);
int __weak __clzsi2(int val)
{
	return 32 - fls(val);
}
EXPORT_SYMBOL(__clzsi2);

int __weak __clzdi2(long val);
int __weak __ctzdi2(long val);
#if BITS_PER_LONG == 32

int __weak __clzdi2(long val)
{
	return 32 - fls((int)val);
}
EXPORT_SYMBOL(__clzdi2);

int __weak __ctzdi2(long val)
{
	return __ffs((u32)val);
}
EXPORT_SYMBOL(__ctzdi2);

#elif BITS_PER_LONG == 64

int __weak __clzdi2(long val)
{
	return 64 - fls64((u64)val);
}
EXPORT_SYMBOL(__clzdi2);

int __weak __ctzdi2(long val)
{
	return __ffs64((u64)val);
}
EXPORT_SYMBOL(__ctzdi2);

#else
#error BITS_PER_LONG not 32 or 64
#endif
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