dax: bdev_direct_access() may sleep

The brd driver is the only in-tree driver that may sleep currently.
After some discussion on linux-fsdevel, we decided that any driver
may choose to sleep in its ->direct_access method.  To ensure that all
callers of bdev_direct_access() are prepared for this, add a call
to might_sleep().

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 5dde6dff4940..12b22ddb22ef 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -445,6 +445,12 @@ long bdev_direct_access(struct block_device *bdev, sector_t sector,
         long avail;
         const struct block_device_operations *ops = bdev->bd_disk->fops;
 
+        /*
+         * The device driver is allowed to sleep, in order to make the
+         * memory directly accessible.
+         */
+        might_sleep();
+
         if (size < 0)
                 return size;
         if (!ops->direct_access)