Re: [PATCH 7/9] btrfs: refactor __btrfs_lookup_bio_sums to use bio_for_each_segment_all

[Omar Sandoval]

On Wed, Nov 16, 2016 at 01:52:14PM +0100, Christoph Hellwig wrote:
> Rework the loop a little bit to use the generic bio_for_each_segment_all
> helper for iterating over the bio.

One minor nit. Besides that,

Reviewed-by: Omar Sandoval 

> Signed-off-by: Christoph Hellwig 
> ---
>  fs/btrfs/file-item.c | 31 +++
>  1 file changed, 11 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index fa8aa53..54ccb91 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -163,7 +163,7 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root 
> *root,
>  struct inode *inode, struct bio *bio,
>  u64 logical_offset, u32 *dst, int dio)
>  {
> - struct bio_vec *bvec = bio->bi_io_vec;
> + struct bio_vec *bvec;
>   struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
>   struct btrfs_csum_item *item = NULL;
>   struct extent_io_tree *io_tree = _I(inode)->io_tree;
> @@ -177,7 +177,7 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root 
> *root,
>   u32 diff;
>   int nblocks;
>   int bio_index = 0;
> - int count;
> + int count = 0;
>   u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
>  
>   path = btrfs_alloc_path();
> @@ -223,8 +223,11 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root 
> *root,
>   if (dio)
>   offset = logical_offset;
>  
> - page_bytes_left = bvec->bv_len;
> - while (bio_index < bio->bi_vcnt) {
> + bio_for_each_segment_all(bvec, bio, bio_index) {

Can we just rename bio_index to i now?

> + page_bytes_left = bvec->bv_len;
> + if (count)
> + goto next;
> +
>   if (!dio)
>   offset = page_offset(bvec->bv_page) + bvec->bv_offset;
>   count = btrfs_find_ordered_sum(inode, offset, disk_bytenr,
> @@ -285,29 +288,17 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root 
> *root,
>  found:
>   csum += count * csum_size;
>   nblocks -= count;
> -
> +next:
>   while (count--) {
>   disk_bytenr += root->sectorsize;
>   offset += root->sectorsize;
>   page_bytes_left -= root->sectorsize;
> - if (!page_bytes_left) {
> - bio_index++;
> - /*
> -  * make sure we're still inside the
> -  * bio before we update page_bytes_left
> -  */
> - if (bio_index >= bio->bi_vcnt) {
> - WARN_ON_ONCE(count);
> - goto done;
> - }
> - bvec++;
> - page_bytes_left = bvec->bv_len;
> - }
> -
> + if (!page_bytes_left)
> + break; /* move to next bio */
>   }
>   }
>  
> -done:
> + WARN_ON_ONCE(count);
>   btrfs_free_path(path);
>   return 0;
>  }
> -- 
> 2.1.4
> 
> --
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-- 
Omar
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[PATCH 7/9] btrfs: refactor __btrfs_lookup_bio_sums to use bio_for_each_segment_all

[Christoph Hellwig]

Rework the loop a little bit to use the generic bio_for_each_segment_all
helper for iterating over the bio.

Signed-off-by: Christoph Hellwig 
---
 fs/btrfs/file-item.c | 31 +++
 1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index fa8aa53..54ccb91 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -163,7 +163,7 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
   struct inode *inode, struct bio *bio,
   u64 logical_offset, u32 *dst, int dio)
 {
-   struct bio_vec *bvec = bio->bi_io_vec;
+   struct bio_vec *bvec;
struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
struct btrfs_csum_item *item = NULL;
struct extent_io_tree *io_tree = _I(inode)->io_tree;
@@ -177,7 +177,7 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
u32 diff;
int nblocks;
int bio_index = 0;
-   int count;
+   int count = 0;
u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 
path = btrfs_alloc_path();
@@ -223,8 +223,11 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
if (dio)
offset = logical_offset;
 
-   page_bytes_left = bvec->bv_len;
-   while (bio_index < bio->bi_vcnt) {
+   bio_for_each_segment_all(bvec, bio, bio_index) {
+   page_bytes_left = bvec->bv_len;
+   if (count)
+   goto next;
+
if (!dio)
offset = page_offset(bvec->bv_page) + bvec->bv_offset;
count = btrfs_find_ordered_sum(inode, offset, disk_bytenr,
@@ -285,29 +288,17 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root 
*root,
 found:
csum += count * csum_size;
nblocks -= count;
-
+next:
while (count--) {
disk_bytenr += root->sectorsize;
offset += root->sectorsize;
page_bytes_left -= root->sectorsize;
-   if (!page_bytes_left) {
-   bio_index++;
-   /*
-* make sure we're still inside the
-* bio before we update page_bytes_left
-*/
-   if (bio_index >= bio->bi_vcnt) {
-   WARN_ON_ONCE(count);
-   goto done;
-   }
-   bvec++;
-   page_bytes_left = bvec->bv_len;
-   }
-
+   if (!page_bytes_left)
+   break; /* move to next bio */
}
}
 
-done:
+   WARN_ON_ONCE(count);
btrfs_free_path(path);
return 0;
 }
-- 
2.1.4

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