[PATCH 1/2] block: invalidate the page cache when issuing BLKZEROOUT.

Darrick J. Wong
2016-03-02T04:10:27Z

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

v5: Refactor the 4.4 refactoring of the ioctl code into separate functions.
Split the page invalidation and the new ioctl into separate patches.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
block/ioctl.c | 29 +++++++++++++++++++++++------
1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index d8996bb..c6eb462 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -226,7 +226,9 @@ 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;
+ int ret;

if (!(mode & FMODE_WRITE))
return -EBADF;
@@ -236,18 +238,33 @@ 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);
+
+ ret = blkdev_issue_zeroout(bdev, start >> 9, len >> 9, GFP_KERNEL,
+ false);
+ if (ret)
+ return ret;
+
+ /*
+ * Invalidate again; if someone wandered in and dirtied a page,
+ * the caller will be given -EBUSY.
+ */
+ return invalidate_inode_pages2_range(mapping,
+ start >> PAGE_CACHE_SHIFT,
+ end >> PAGE_CACHE_SHIFT);
}

static int put_ushort(unsigned long arg, unsigned short val)