[PATCH 1/3] block: invalidate the page cache when issuing BLKZEROOUT.

["Darrick J. Wong" <darrick.wong@xxxxxxxxxx>]

Invalidate the page cache (as a regular O_DIRECT write would do) to avoid
returning stale cache contents at a later time.

Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
 block/ioctl.c |   18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)


diff --git a/block/ioctl.c b/block/ioctl.c
index ed2397f..755119c 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -225,7 +225,8 @@ static int blk_ioctl_zeroout(struct block_device *bdev, 
fmode_t mode,
                unsigned long arg)
 {
        uint64_t range[2];
-       uint64_t start, len;
+       struct address_space *mapping;
+       uint64_t start, end, len;
 
        if (!(mode & FMODE_WRITE))
                return -EBADF;
@@ -235,18 +236,23 @@ static int blk_ioctl_zeroout(struct block_device *bdev, 
fmode_t mode,
 
        start = range[0];
        len = range[1];
+       end = start + len - 1;
 
        if (start & 511)
                return -EINVAL;
        if (len & 511)
                return -EINVAL;
-       start >>= 9;
-       len >>= 9;
-
-       if (start + len > (i_size_read(bdev->bd_inode) >> 9))
+       if (end >= (uint64_t)i_size_read(bdev->bd_inode))
+               return -EINVAL;
+       if (end < start)
                return -EINVAL;
 
-       return blkdev_issue_zeroout(bdev, start, len, GFP_KERNEL, false);
+       /* Invalidate the page cache, including dirty pages */
+       mapping = bdev->bd_inode->i_mapping;
+       truncate_inode_pages_range(mapping, start, end);
+
+       return blkdev_issue_zeroout(bdev, start >> 9, len >> 9, GFP_KERNEL,
+                                   false);
 }
 
 static int put_ushort(unsigned long arg, unsigned short val)