diff options
authorMatthew Wilcox <>2015-07-03 10:40:38 -0400
committerAl Viro <>2015-07-04 15:56:56 -0400
commit44f4c054cae646a9296da05cdfe7d6e786f73d46 (patch)
parent5ba97d2832f87943c43bb69cb1ef86dbc59df5bc (diff)
dax: Add block size note to documentation
For block devices which are small enough, mkfs will default to creating a filesystem with block sizes smaller than page size. Signed-off-by: Matthew Wilcox <> Signed-off-by: Al Viro <>
1 files changed, 4 insertions, 2 deletions
diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt
index baf41118660d..7af2851d667c 100644
--- a/Documentation/filesystems/dax.txt
+++ b/Documentation/filesystems/dax.txt
@@ -18,8 +18,10 @@ Usage
If you have a block device which supports DAX, you can make a filesystem
-on it as usual. When mounting it, use the -o dax option manually
-or add 'dax' to the options in /etc/fstab.
+on it as usual. The DAX code currently only supports files with a block
+size equal to your kernel's PAGE_SIZE, so you may need to specify a block
+size when creating the filesystem. When mounting it, use the "-o dax"
+option on the command line or add 'dax' to the options in /etc/fstab.
Implementation Tips for Block Driver Writers