On 06/17/2016 03:18 AM, Darrick J. Wong wrote:
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@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
block/ioctl.c | 29 +++++++++++++++++++++++------
1 file changed, 23 insertions(+), 6 deletions(-)
diff --git a/block/ioctl.c b/block/ioctl.c
index ed2397f..d001f52 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -225,7 +225,9 @@ 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;
@@ -235,18 +237,33 @@ 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_SHIFT,
+ end >> PAGE_SHIFT);
}
Hello Darrick,
Maybe this has already been discussed, but anyway: in the POSIX spec
(http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html) I
found the following: "This volume of POSIX.1-2008 does not specify
behavior of concurrent writes to a file from multiple processes.
Applications should use some form of concurrency control."
Do we really need the invalidate_inode_pages2_range() call?
Thanks,
Bart.
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