On 10/02/2014 10:09 AM, Thanos Makatos wrote:
> This patch introduces a new ioctl called BLKFLUSHBUFS2, which is pretty
> similar to BLKFLUSHBUFS except that is also invalidates the page cache.
> This allows for a complete invalidation of the cached data of a
> particular block device, which might be useful for cases like
> synchronising the caches of an iSCSI block device used by multiple
> hosts.
>
> Signed-off-by: Thanos Makatos <thanos.maka...@citrix.com>
> ---
> block/compat_ioctl.c | 1 +
> block/ioctl.c | 13 +++++++++++--
> include/uapi/linux/fs.h | 1 +
> 3 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
> index 18b282c..672388ab 100644
> --- a/block/compat_ioctl.c
> +++ b/block/compat_ioctl.c
> @@ -688,6 +688,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd,
> unsigned long arg)
> case BLKDISCARDZEROES:
> return compat_put_uint(arg, bdev_discard_zeroes_data(bdev));
> case BLKFLSBUF:
> + case BLKFLSBUF2:
> case BLKROSET:
> case BLKDISCARD:
> case BLKSECDISCARD:
> diff --git a/block/ioctl.c b/block/ioctl.c
> index d6cda81..0c427a7 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -268,6 +268,12 @@ static inline int is_unrecognized_ioctl(int ret)
> ret == -ENOIOCTLCMD;
> }
>
> +static void flush_buffer_cache(struct block_device *bdev)
> +{
> + fsync_bdev(bdev);
> + invalidate_bdev(bdev);
> +}
> +
> /*
> * always keep this in sync with compat_blkdev_ioctl()
> */
> @@ -282,6 +288,7 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode,
> unsigned cmd,
>
> switch(cmd) {
> case BLKFLSBUF:
> + case BLKFLSBUF2:
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
>
> @@ -289,8 +296,10 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t
> mode, unsigned cmd,
> if (!is_unrecognized_ioctl(ret))
> return ret;
>
> - fsync_bdev(bdev);
> - invalidate_bdev(bdev);
> + flush_buffer_cache(bdev);
> + if (BLKFLSBUF2 == cmd)
> + return invalidate_inode_pages2(
> + bdev->bd_inode->i_mapping);
> return 0;
We're currently ignoring the buffer cache sync and invalidation (which
is odd), but at least being consistent would be good.
Might also need a filemap_write_and_wait() to sync before invalidation.
--
Jens Axboe
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