diff mbox series

[08/16] dm-writecache: use bvec_kmap_local instead of bvec_kmap_irq

Message ID 20210608160603.1535935-9-hch@lst.de (mailing list archive)
State New, archived
Headers show
Series [01/16] mm: use kmap_local_page in memzero_page | expand

Commit Message

Christoph Hellwig June 8, 2021, 4:05 p.m. UTC
There is no need to disable interrupts in bio_copy_block, and the local
only mappings helps to avoid any sort of problems with stray writes
into the bio data.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-writecache.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Comments

Bart Van Assche June 8, 2021, 4:30 p.m. UTC | #1
On 6/8/21 9:05 AM, Christoph Hellwig wrote:
> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
> index aecc246ade26..93ca454eaca9 100644
> --- a/drivers/md/dm-writecache.c
> +++ b/drivers/md/dm-writecache.c
> @@ -1205,14 +1205,13 @@ static void memcpy_flushcache_optimized(void *dest, void *source, size_t size)
>  static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data)
>  {
>  	void *buf;
> -	unsigned long flags;
>  	unsigned size;
>  	int rw = bio_data_dir(bio);
>  	unsigned remaining_size = wc->block_size;
>  
>  	do {
>  		struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
> -		buf = bvec_kmap_irq(&bv, &flags);
> +		buf = bvec_kmap_local(&bv);
>  		size = bv.bv_len;
>  		if (unlikely(size > remaining_size))
>  			size = remaining_size;
> @@ -1230,7 +1229,7 @@ static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data
>  			memcpy_flushcache_optimized(data, buf, size);
>  		}
>  
> -		bvec_kunmap_irq(buf, &flags);
> +		kunmap_local(buf);
>  
>  		data = (char *)data + size;
>  		remaining_size -= size;

From one of the functions called by kunmap_local():

unsigned long addr = (unsigned long) vaddr & PAGE_MASK;

This won't work well if bvec->bv_offset >= PAGE_SIZE I assume?

Thanks,

Bart.
Christoph Hellwig June 8, 2021, 4:38 p.m. UTC | #2
On Tue, Jun 08, 2021 at 09:30:56AM -0700, Bart Van Assche wrote:
> >From one of the functions called by kunmap_local():
> 
> unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
> 
> This won't work well if bvec->bv_offset >= PAGE_SIZE I assume?

It won't indeed.  Both the existing and new helpers operate on single
page bvecs only, and all callers only use those.  I should have
probably mentioned that in the cover letter and documented the
assumptions in the code, though.
diff mbox series

Patch

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index aecc246ade26..93ca454eaca9 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -1205,14 +1205,13 @@  static void memcpy_flushcache_optimized(void *dest, void *source, size_t size)
 static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data)
 {
 	void *buf;
-	unsigned long flags;
 	unsigned size;
 	int rw = bio_data_dir(bio);
 	unsigned remaining_size = wc->block_size;
 
 	do {
 		struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
-		buf = bvec_kmap_irq(&bv, &flags);
+		buf = bvec_kmap_local(&bv);
 		size = bv.bv_len;
 		if (unlikely(size > remaining_size))
 			size = remaining_size;
@@ -1230,7 +1229,7 @@  static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data
 			memcpy_flushcache_optimized(data, buf, size);
 		}
 
-		bvec_kunmap_irq(buf, &flags);
+		kunmap_local(buf);
 
 		data = (char *)data + size;
 		remaining_size -= size;