path: root/block
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authorDan Williams <>2016-02-26 15:19:43 -0800
committerLinus Torvalds <>2016-02-27 10:28:52 -0800
commit03cdadb04077b9311bbc67d98cc5401aff76482d (patch)
tree75f29115e158d12d246751f4f241504a596395bd /block
parenta4a8481ff68a8a324a878e281bc37f18665224f7 (diff)
block: disable block device DAX by default
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 <> Signed-off-by: Ross Zwisler <> Reported-by: Ross Zwisler <> Suggested-by: Dave Chinner <> Reviewed-by: Jan Kara <> Cc: Jens Axboe <> Cc: Matthew Wilcox <> Cc: Al Viro <> Cc: Theodore Ts'o <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'block')
1 files changed, 13 insertions, 0 deletions
diff --git a/block/Kconfig b/block/Kconfig
index 161491d0a879..0363cd731320 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -88,6 +88,19 @@ config BLK_DEV_INTEGRITY
T10/SCSI Data Integrity Field or the T13/ATA External Path
Protection. If in doubt, say N.
+config BLK_DEV_DAX
+ bool "Block device DAX support"
+ depends on FS_DAX
+ depends on BROKEN
+ help
+ When DAX support is available (CONFIG_FS_DAX) raw block
+ devices can also support direct userspace access to the
+ storage capacity via MMAP(2) similar to a file on a
+ DAX-enabled filesystem. However, the DAX I/O-path disables
+ some standard I/O-statistics, and the MMAP(2) path has some
+ operational differences due to bypassing the page
+ cache. If in doubt, say N.
bool "Block layer bio throttling support"
depends on BLK_CGROUP=y