[PATCH v2 0/4] xen/blkback: some cleanups

[PATCH v2 0/4] xen/blkback: some cleanups

[Juergen Gross]

Some small cleanup patches I had lying around for some time now.

Juergen Gross (4):
  xen/blkback: fix white space code style issues
  xen/blkback: remove stale prototype
  xen/blkback: simplify free_persistent_gnts() interface
  xen/blkback: move blkif_get_x86_*_req() into blkback.c

 drivers/block/xen-blkback/blkback.c | 126 +++++++++++++++++++++++++---
 drivers/block/xen-blkback/common.h  | 103 +----------------------
 2 files changed, 118 insertions(+), 111 deletions(-)

-- 
2.35.3

[PATCH v2 1/4] xen/blkback: fix white space code style issues

[Juergen Gross]

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
---
 drivers/block/xen-blkback/blkback.c | 2 +-
 drivers/block/xen-blkback/common.h  | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index a5cf7f1e871c..6e2163aaf362 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -891,7 +891,7 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
 out:
 	for (i = last_map; i < num; i++) {
 		/* Don't zap current batch's valid persistent grants. */
-		if(i >= map_until)
+		if (i >= map_until)
 			pages[i]->persistent_gnt = NULL;
 		pages[i]->handle = BLKBACK_INVALID_HANDLE;
 	}
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index a28473470e66..9a13a6b420a6 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -296,7 +296,7 @@ struct xen_blkif_ring {
 	struct work_struct	free_work;
 	/* Thread shutdown wait queue. */
 	wait_queue_head_t	shutdown_wq;
-	struct xen_blkif 	*blkif;
+	struct xen_blkif	*blkif;
 };
 
 struct xen_blkif {
@@ -315,7 +315,7 @@ struct xen_blkif {
 	atomic_t		drain;
 
 	struct work_struct	free_work;
-	unsigned int 		nr_ring_pages;
+	unsigned int		nr_ring_pages;
 	bool			multi_ref;
 	/* All rings for this device. */
 	struct xen_blkif_ring	*rings;
@@ -329,7 +329,7 @@ struct seg_buf {
 };
 
 struct grant_page {
-	struct page 		*page;
+	struct page		*page;
 	struct persistent_gnt	*persistent_gnt;
 	grant_handle_t		handle;
 	grant_ref_t		gref;
-- 
2.35.3

[PATCH v2 2/4] xen/blkback: remove stale prototype

[Juergen Gross]

There is no function xen_blkif_purge_persistent(), so remove its
prototype from common.h.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
---
 drivers/block/xen-blkback/common.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 9a13a6b420a6..fab8a8dee0da 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -384,7 +384,6 @@ void xen_blkif_xenbus_fini(void);
 
 irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
 int xen_blkif_schedule(void *arg);
-int xen_blkif_purge_persistent(void *arg);
 void xen_blkbk_free_caches(struct xen_blkif_ring *ring);
 
 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
-- 
2.35.3

[PATCH v2 3/4] xen/blkback: simplify free_persistent_gnts() interface

[Juergen Gross]

The interface of free_persistent_gnts() can be simplified, as there is
only a single caller of free_persistent_gnts() and the 2nd and 3rd
parameters are easily obtainable via the ring pointer, which is passed
as the first parameter anyway.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
---
 drivers/block/xen-blkback/blkback.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 6e2163aaf362..243712b59a05 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -239,9 +239,9 @@ static void put_persistent_gnt(struct xen_blkif_ring *ring,
 	atomic_dec(&ring->persistent_gnt_in_use);
 }
 
-static void free_persistent_gnts(struct xen_blkif_ring *ring, struct rb_root *root,
-                                 unsigned int num)
+static void free_persistent_gnts(struct xen_blkif_ring *ring)
 {
+	struct rb_root *root = &ring->persistent_gnts;
 	struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	struct persistent_gnt *persistent_gnt;
@@ -249,6 +249,9 @@ static void free_persistent_gnts(struct xen_blkif_ring *ring, struct rb_root *ro
 	int segs_to_unmap = 0;
 	struct gntab_unmap_queue_data unmap_data;
 
+	if (RB_EMPTY_ROOT(root))
+		return;
+
 	unmap_data.pages = pages;
 	unmap_data.unmap_ops = unmap;
 	unmap_data.kunmap_ops = NULL;
@@ -277,9 +280,11 @@ static void free_persistent_gnts(struct xen_blkif_ring *ring, struct rb_root *ro
 
 		rb_erase(&persistent_gnt->node, root);
 		kfree(persistent_gnt);
-		num--;
+		ring->persistent_gnt_c--;
 	}
-	BUG_ON(num != 0);
+
+	BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
+	BUG_ON(ring->persistent_gnt_c != 0);
 }
 
 void xen_blkbk_unmap_purged_grants(struct work_struct *work)
@@ -631,12 +636,7 @@ int xen_blkif_schedule(void *arg)
 void xen_blkbk_free_caches(struct xen_blkif_ring *ring)
 {
 	/* Free all persistent grant pages */
-	if (!RB_EMPTY_ROOT(&ring->persistent_gnts))
-		free_persistent_gnts(ring, &ring->persistent_gnts,
-			ring->persistent_gnt_c);
-
-	BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
-	ring->persistent_gnt_c = 0;
+	free_persistent_gnts(ring);
 
 	/* Since we are shutting down remove all pages from the buffer */
 	gnttab_page_cache_shrink(&ring->free_pages, 0 /* All */);
-- 
2.35.3

[PATCH v2 4/4] xen/blkback: move blkif_get_x86_*_req() into blkback.c

[Juergen Gross]

There is no need to have the functions blkif_get_x86_32_req() and
blkif_get_x86_64_req() in a header file, as they are used in one place
only.

So move them into the using source file and drop the inline qualifier.

While at it fix some style issues, and simplify the code by variable
reusing and using min() instead of open coding it.

Instead of using barrier() use READ_ONCE() for avoiding multiple reads
of nr_segments.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
---
V2:
- add const, use unsigned int for loop counters (Roger Pau Monné)
---
 drivers/block/xen-blkback/blkback.c | 104 ++++++++++++++++++++++++++++
 drivers/block/xen-blkback/common.h  |  96 -------------------------
 2 files changed, 104 insertions(+), 96 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 243712b59a05..ab6308b2d328 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -1072,7 +1072,111 @@ static void end_block_io_op(struct bio *bio)
 	bio_put(bio);
 }
 
+static void blkif_get_x86_32_req(struct blkif_request *dst,
+				 const struct blkif_x86_32_request *src)
+{
+	unsigned int i, n;
+
+	dst->operation = READ_ONCE(src->operation);
+
+	switch (dst->operation) {
+	case BLKIF_OP_READ:
+	case BLKIF_OP_WRITE:
+	case BLKIF_OP_WRITE_BARRIER:
+	case BLKIF_OP_FLUSH_DISKCACHE:
+		dst->u.rw.nr_segments = READ_ONCE(src->u.rw.nr_segments);
+		dst->u.rw.handle = src->u.rw.handle;
+		dst->u.rw.id = src->u.rw.id;
+		dst->u.rw.sector_number = src->u.rw.sector_number;
+		n = min_t(unsigned int, BLKIF_MAX_SEGMENTS_PER_REQUEST,
+			  dst->u.rw.nr_segments);
+		for (i = 0; i < n; i++)
+			dst->u.rw.seg[i] = src->u.rw.seg[i];
+		break;
+
+	case BLKIF_OP_DISCARD:
+		dst->u.discard.flag = src->u.discard.flag;
+		dst->u.discard.id = src->u.discard.id;
+		dst->u.discard.sector_number = src->u.discard.sector_number;
+		dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
+		break;
+
+	case BLKIF_OP_INDIRECT:
+		dst->u.indirect.indirect_op = src->u.indirect.indirect_op;
+		dst->u.indirect.nr_segments =
+			READ_ONCE(src->u.indirect.nr_segments);
+		dst->u.indirect.handle = src->u.indirect.handle;
+		dst->u.indirect.id = src->u.indirect.id;
+		dst->u.indirect.sector_number = src->u.indirect.sector_number;
+		n = min(MAX_INDIRECT_PAGES,
+			INDIRECT_PAGES(dst->u.indirect.nr_segments));
+		for (i = 0; i < n; i++)
+			dst->u.indirect.indirect_grefs[i] =
+				src->u.indirect.indirect_grefs[i];
+		break;
+
+	default:
+		/*
+		 * Don't know how to translate this op. Only get the
+		 * ID so failure can be reported to the frontend.
+		 */
+		dst->u.other.id = src->u.other.id;
+		break;
+	}
+}
 
+static void blkif_get_x86_64_req(struct blkif_request *dst,
+				 struct blkif_x86_64_request *src)
+{
+	int i, n;
+
+	dst->operation = READ_ONCE(src->operation);
+
+	switch (dst->operation) {
+	case BLKIF_OP_READ:
+	case BLKIF_OP_WRITE:
+	case BLKIF_OP_WRITE_BARRIER:
+	case BLKIF_OP_FLUSH_DISKCACHE:
+		dst->u.rw.nr_segments = READ_ONCE(src->u.rw.nr_segments);
+		dst->u.rw.handle = src->u.rw.handle;
+		dst->u.rw.id = src->u.rw.id;
+		dst->u.rw.sector_number = src->u.rw.sector_number;
+		n = min_t(int, BLKIF_MAX_SEGMENTS_PER_REQUEST,
+			  dst->u.rw.nr_segments);
+		for (i = 0; i < n; i++)
+			dst->u.rw.seg[i] = src->u.rw.seg[i];
+		break;
+
+	case BLKIF_OP_DISCARD:
+		dst->u.discard.flag = src->u.discard.flag;
+		dst->u.discard.id = src->u.discard.id;
+		dst->u.discard.sector_number = src->u.discard.sector_number;
+		dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
+		break;
+
+	case BLKIF_OP_INDIRECT:
+		dst->u.indirect.indirect_op = src->u.indirect.indirect_op;
+		dst->u.indirect.nr_segments =
+			READ_ONCE(src->u.indirect.nr_segments);
+		dst->u.indirect.handle = src->u.indirect.handle;
+		dst->u.indirect.id = src->u.indirect.id;
+		dst->u.indirect.sector_number = src->u.indirect.sector_number;
+		n = min(MAX_INDIRECT_PAGES,
+			INDIRECT_PAGES(dst->u.indirect.nr_segments));
+		for (i = 0; i < n; i++)
+			dst->u.indirect.indirect_grefs[i] =
+				src->u.indirect.indirect_grefs[i];
+		break;
+
+	default:
+		/*
+		 * Don't know how to translate this op. Only get the
+		 * ID so failure can be reported to the frontend.
+		 */
+		dst->u.other.id = src->u.other.id;
+		break;
+	}
+}
 
 /*
  * Function to copy the from the ring buffer the 'struct blkif_request'
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index fab8a8dee0da..40f67bfc052d 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -394,100 +394,4 @@ int xen_blkbk_barrier(struct xenbus_transaction xbt,
 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be);
 void xen_blkbk_unmap_purged_grants(struct work_struct *work);
 
-static inline void blkif_get_x86_32_req(struct blkif_request *dst,
-					struct blkif_x86_32_request *src)
-{
-	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST, j;
-	dst->operation = READ_ONCE(src->operation);
-	switch (dst->operation) {
-	case BLKIF_OP_READ:
-	case BLKIF_OP_WRITE:
-	case BLKIF_OP_WRITE_BARRIER:
-	case BLKIF_OP_FLUSH_DISKCACHE:
-		dst->u.rw.nr_segments = src->u.rw.nr_segments;
-		dst->u.rw.handle = src->u.rw.handle;
-		dst->u.rw.id = src->u.rw.id;
-		dst->u.rw.sector_number = src->u.rw.sector_number;
-		barrier();
-		if (n > dst->u.rw.nr_segments)
-			n = dst->u.rw.nr_segments;
-		for (i = 0; i < n; i++)
-			dst->u.rw.seg[i] = src->u.rw.seg[i];
-		break;
-	case BLKIF_OP_DISCARD:
-		dst->u.discard.flag = src->u.discard.flag;
-		dst->u.discard.id = src->u.discard.id;
-		dst->u.discard.sector_number = src->u.discard.sector_number;
-		dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
-		break;
-	case BLKIF_OP_INDIRECT:
-		dst->u.indirect.indirect_op = src->u.indirect.indirect_op;
-		dst->u.indirect.nr_segments = src->u.indirect.nr_segments;
-		dst->u.indirect.handle = src->u.indirect.handle;
-		dst->u.indirect.id = src->u.indirect.id;
-		dst->u.indirect.sector_number = src->u.indirect.sector_number;
-		barrier();
-		j = min(MAX_INDIRECT_PAGES, INDIRECT_PAGES(dst->u.indirect.nr_segments));
-		for (i = 0; i < j; i++)
-			dst->u.indirect.indirect_grefs[i] =
-				src->u.indirect.indirect_grefs[i];
-		break;
-	default:
-		/*
-		 * Don't know how to translate this op. Only get the
-		 * ID so failure can be reported to the frontend.
-		 */
-		dst->u.other.id = src->u.other.id;
-		break;
-	}
-}
-
-static inline void blkif_get_x86_64_req(struct blkif_request *dst,
-					struct blkif_x86_64_request *src)
-{
-	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST, j;
-	dst->operation = READ_ONCE(src->operation);
-	switch (dst->operation) {
-	case BLKIF_OP_READ:
-	case BLKIF_OP_WRITE:
-	case BLKIF_OP_WRITE_BARRIER:
-	case BLKIF_OP_FLUSH_DISKCACHE:
-		dst->u.rw.nr_segments = src->u.rw.nr_segments;
-		dst->u.rw.handle = src->u.rw.handle;
-		dst->u.rw.id = src->u.rw.id;
-		dst->u.rw.sector_number = src->u.rw.sector_number;
-		barrier();
-		if (n > dst->u.rw.nr_segments)
-			n = dst->u.rw.nr_segments;
-		for (i = 0; i < n; i++)
-			dst->u.rw.seg[i] = src->u.rw.seg[i];
-		break;
-	case BLKIF_OP_DISCARD:
-		dst->u.discard.flag = src->u.discard.flag;
-		dst->u.discard.id = src->u.discard.id;
-		dst->u.discard.sector_number = src->u.discard.sector_number;
-		dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
-		break;
-	case BLKIF_OP_INDIRECT:
-		dst->u.indirect.indirect_op = src->u.indirect.indirect_op;
-		dst->u.indirect.nr_segments = src->u.indirect.nr_segments;
-		dst->u.indirect.handle = src->u.indirect.handle;
-		dst->u.indirect.id = src->u.indirect.id;
-		dst->u.indirect.sector_number = src->u.indirect.sector_number;
-		barrier();
-		j = min(MAX_INDIRECT_PAGES, INDIRECT_PAGES(dst->u.indirect.nr_segments));
-		for (i = 0; i < j; i++)
-			dst->u.indirect.indirect_grefs[i] =
-				src->u.indirect.indirect_grefs[i];
-		break;
-	default:
-		/*
-		 * Don't know how to translate this op. Only get the
-		 * ID so failure can be reported to the frontend.
-		 */
-		dst->u.other.id = src->u.other.id;
-		break;
-	}
-}
-
 #endif /* __XEN_BLKIF__BACKEND__COMMON_H__ */
-- 
2.35.3

Re: [PATCH v2 4/4] xen/blkback: move blkif_get_x86_*_req() into blkback.c

[Jan Beulich]

On 14.03.2023 15:27, Juergen Gross wrote:
> V2:
> - add const, use unsigned int for loop counters (Roger Pau Monné)

Hmm, ...

> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -1072,7 +1072,111 @@ static void end_block_io_op(struct bio *bio)
>  	bio_put(bio);
>  }
>  
> +static void blkif_get_x86_32_req(struct blkif_request *dst,
> +				 const struct blkif_x86_32_request *src)
> +{
> +	unsigned int i, n;

... here you did, but ...

> +static void blkif_get_x86_64_req(struct blkif_request *dst,
> +				 struct blkif_x86_64_request *src)
> +{
> +	int i, n;

... what about these?

Jan

Re: [PATCH v2 4/4] xen/blkback: move blkif_get_x86_*_req() into blkback.c

[Juergen Gross]

[-- Attachment #1.1.1: Type: text/plain, Size: 896 bytes --]

On 14.03.23 15:33, Jan Beulich wrote:
> On 14.03.2023 15:27, Juergen Gross wrote:
>> V2:
>> - add const, use unsigned int for loop counters (Roger Pau Monné)
> 
> Hmm, ...
> 
>> --- a/drivers/block/xen-blkback/blkback.c
>> +++ b/drivers/block/xen-blkback/blkback.c
>> @@ -1072,7 +1072,111 @@ static void end_block_io_op(struct bio *bio)
>>   	bio_put(bio);
>>   }
>>   
>> +static void blkif_get_x86_32_req(struct blkif_request *dst,
>> +				 const struct blkif_x86_32_request *src)
>> +{
>> +	unsigned int i, n;
> 
> ... here you did, but ...
> 
>> +static void blkif_get_x86_64_req(struct blkif_request *dst,
>> +				 struct blkif_x86_64_request *src)
>> +{
>> +	int i, n;
> 
> ... what about these?

Oh, indeed. I could say Roger commented only on blkif_get_x86_32_req(), but this
would be a rather lame excuse. ;-)

I'll resend that last patch.


Juergen


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