[PATCHv12 06/12] block: expose write streams for block device nodes

[Nitesh Shetty]

On 06/12/24 02:17PM, Keith Busch wrote:
>From: Christoph Hellwig <hch at lst.de>
>
>Export statx information about the number and granularity of write
>streams, use the per-kiocb write hint and map temperature hints
>to write streams (which is a bit questionable, but this shows how it is
>done).
>
>Signed-off-by: Christoph Hellwig <hch at lst.de>
>Signed-off-by: Keith Busch <kbusch at kernel.org>
>---
> block/bdev.c |  6 ++++++
> block/fops.c | 23 +++++++++++++++++++++++
> 2 files changed, 29 insertions(+)
>
>diff --git a/block/bdev.c b/block/bdev.c
>index 738e3c8457e7f..c23245f1fdfe3 100644
>--- a/block/bdev.c
>+++ b/block/bdev.c
>@@ -1296,6 +1296,12 @@ void bdev_statx(struct path *path, struct kstat *stat,
> 		stat->result_mask |= STATX_DIOALIGN;
> 	}
>
>+	if ((request_mask & STATX_WRITE_STREAM) &&
We may not reach this point, if user application doesn't set either of
STATX_DIOALIGN or STATX_WRITE_ATOMIC.

>+	    bdev_max_write_streams(bdev)) {
>+		stat->write_stream_max = bdev_max_write_streams(bdev);
>+		stat->result_mask |= STATX_WRITE_STREAM;
statx will show value of 0 for write_stream_granularity.

Below is the fix which might help you,

diff --git a/block/bdev.c b/block/bdev.c
index c23245f1fdfe..290577e20457 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -1275,7 +1275,8 @@ void bdev_statx(struct path *path, struct kstat *stat,
  	struct inode *backing_inode;
  	struct block_device *bdev;
  
-	if (!(request_mask & (STATX_DIOALIGN | STATX_WRITE_ATOMIC)))
+	if (!(request_mask & (STATX_DIOALIGN | STATX_WRITE_ATOMIC |
+		STATX_WRITE_STREAM)))
  		return;
  
  	backing_inode = d_backing_inode(path->dentry);
@@ -1299,6 +1300,7 @@ void bdev_statx(struct path *path, struct kstat *stat,
  	if ((request_mask & STATX_WRITE_STREAM) &&
  	    bdev_max_write_streams(bdev)) {
  		stat->write_stream_max = bdev_max_write_streams(bdev);
+		stat->write_stream_granularity = bdev_write_stream_granularity(bdev);
  		stat->result_mask |= STATX_WRITE_STREAM;
  	}