On Mon, Jun 20, 2016 at 02:35:29PM +0200, Bart Van Assche wrote: > 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 <[email protected]> > >Reviewed-by: Christoph Hellwig <[email protected]> > >--- > > 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?
It's not strictly necessary. I like the idea of having the kernel bonking userspace when they don't coordinate and collide, but we could just jump out after the blkdev_*() calls and let userspace fend for themselves. :) --D > > Thanks, > > Bart. > -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
