[PATCH 0/3] Simplify counting of extent buffer pages

[PATCH 0/3] Simplify counting of extent buffer pages

[David Sterba]

Some low-hanging cleanup fruit. The argument bloat-o-meter shows some
improvements:

extent_io.c:cache_state_if_flags.part.27       -8 (8 -> 0)
extent_io.c:cache_state.part.28                -8 (8 -> 0)
extent_io.c:check_buffer_tree_ref.part.31     -24 (24 -> 0)
extent_io.c:mark_extent_buffer_accessed        -8 (40 -> 32)
extent_io.c:alloc_extent_state_atomic.part.35  -8 (8 -> 0)
extent_io.c:flush_write_bio.isra.40           -16 (16 -> 0)
extent_io.c:set_page_extent_mapped.part.49     -8 (8 -> 0)
extent_io.c:extent_buffer_under_io.part.50     -8 (8 -> 0)
extent_io.c:__unlock_for_delalloc.isra.38      -8 (8 -> 0)
extent_io.c:merge_state.part.45               -48 (48 -> 0)
extent_io.c:repair_eb_io_failure               -8 (72 -> 64)
extent_io.c:set_extent_buffer_dirty            -8 (40 -> 32)
extent_io.c:__alloc_dummy_extent_buffer        +8 (32 -> 40)
extent_io.c:write_one_eb                      +16 (152 -> 168)

David Sterba (3):
  btrfs: simplify counting number of eb pages
  btrfs: pass only eb to num_extent_pages
  btrfs: switch types to int when counting eb pages

 fs/btrfs/extent_io.c | 68 ++++++++++++++++++++++++++--------------------------
 fs/btrfs/extent_io.h |  5 ++--
 2 files changed, 36 insertions(+), 37 deletions(-)

-- 
2.16.2

[PATCH 1/3] btrfs: simplify counting number of eb pages

[David Sterba]

The eb length is nodesize, as initialized in __alloc_extent_buffer.
Regardless of start, we should always get the same number of pages, so
use that fact.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/extent_io.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index a53009694b16..ee92c1289edd 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -454,8 +454,7 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
 
 static inline unsigned long num_extent_pages(u64 start, u64 len)
 {
-	return ((start + len + PAGE_SIZE - 1) >> PAGE_SHIFT) -
-		(start >> PAGE_SHIFT);
+	return len >> PAGE_SHIFT;
 }
 
 static inline void extent_buffer_get(struct extent_buffer *eb)
-- 
2.16.2

Re: [PATCH 1/3] btrfs: simplify counting number of eb pages

[Nikolay Borisov]

On 24.04.2018 02:03, David Sterba wrote:
> The eb length is nodesize, as initialized in __alloc_extent_buffer.
> Regardless of start, we should always get the same number of pages, so
> use that fact.
> 
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/extent_io.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index a53009694b16..ee92c1289edd 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -454,8 +454,7 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
>  
>  static inline unsigned long num_extent_pages(u64 start, u64 len)
>  {
> -	return ((start + len + PAGE_SIZE - 1) >> PAGE_SHIFT) -
> -		(start >> PAGE_SHIFT);
> +	return len >> PAGE_SHIFT;

Shouldn't this really be len + PAGE_SIZE -1 or in fact DIV_ROUND_DOWN
(len, PAGE_SIZE). Because with a nodesize of 4k (and basically less than
a page size) we can get into a situation where we do:

4096 >> 13 = 0

On powerpc for example we have:

arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              18
arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              16
arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              14
arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              12


>  }
>  
>  static inline void extent_buffer_get(struct extent_buffer *eb)
> 

Re: [PATCH 1/3] btrfs: simplify counting number of eb pages

[Qu Wenruo]

On 2018年04月24日 13:59, Nikolay Borisov wrote:
> 
> 
> On 24.04.2018 02:03, David Sterba wrote:
>> The eb length is nodesize, as initialized in __alloc_extent_buffer.
>> Regardless of start, we should always get the same number of pages, so
>> use that fact.
>>
>> Signed-off-by: David Sterba <dsterba@suse.com>
>> ---
>>  fs/btrfs/extent_io.h | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
>> index a53009694b16..ee92c1289edd 100644
>> --- a/fs/btrfs/extent_io.h
>> +++ b/fs/btrfs/extent_io.h
>> @@ -454,8 +454,7 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
>>  
>>  static inline unsigned long num_extent_pages(u64 start, u64 len)
>>  {
>> -	return ((start + len + PAGE_SIZE - 1) >> PAGE_SHIFT) -
>> -		(start >> PAGE_SHIFT);
>> +	return len >> PAGE_SHIFT;
> 
> Shouldn't this really be len + PAGE_SIZE -1 or in fact DIV_ROUND_DOWN
> (len, PAGE_SIZE). Because with a nodesize of 4k (and basically less than
> a page size) we can get into a situation where we do:
> 
> 4096 >> 13 = 0
> 
> On powerpc for example we have:
> 
> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              18
> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              16
> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              14

For such case, the fs won't be mounted as we don't have sub-pagesized
nodesize support yet.
So won't hit the problem.

Although a WARN_ON(len < PAGE_SIZE || IS_ALIGNED(start, PAGE_SIZE))
would do no harm here.

Thanks,
Qu

> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              12
> 
> 
>>  }
>>  
>>  static inline void extent_buffer_get(struct extent_buffer *eb)
>>
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> 

Re: [PATCH 1/3] btrfs: simplify counting number of eb pages

[David Sterba]

On Tue, Apr 24, 2018 at 02:22:15PM +0800, Qu Wenruo wrote:
> 
> 
> On 2018年04月24日 13:59, Nikolay Borisov wrote:
> > 
> > 
> > On 24.04.2018 02:03, David Sterba wrote:
> >> The eb length is nodesize, as initialized in __alloc_extent_buffer.
> >> Regardless of start, we should always get the same number of pages, so
> >> use that fact.
> >>
> >> Signed-off-by: David Sterba <dsterba@suse.com>
> >> ---
> >>  fs/btrfs/extent_io.h | 3 +--
> >>  1 file changed, 1 insertion(+), 2 deletions(-)
> >>
> >> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> >> index a53009694b16..ee92c1289edd 100644
> >> --- a/fs/btrfs/extent_io.h
> >> +++ b/fs/btrfs/extent_io.h
> >> @@ -454,8 +454,7 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
> >>  
> >>  static inline unsigned long num_extent_pages(u64 start, u64 len)
> >>  {
> >> -	return ((start + len + PAGE_SIZE - 1) >> PAGE_SHIFT) -
> >> -		(start >> PAGE_SHIFT);
> >> +	return len >> PAGE_SHIFT;
> > 
> > Shouldn't this really be len + PAGE_SIZE -1 or in fact DIV_ROUND_DOWN
> > (len, PAGE_SIZE). Because with a nodesize of 4k (and basically less than
> > a page size) we can get into a situation where we do:
> > 
> > 4096 >> 13 = 0
> > 
> > On powerpc for example we have:
> > 
> > arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              18
> > arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              16
> > arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              14
> 
> For such case, the fs won't be mounted as we don't have sub-pagesized
> nodesize support yet.
> So won't hit the problem.
> 
> Although a WARN_ON(len < PAGE_SIZE || IS_ALIGNED(start, PAGE_SIZE))
> would do no harm here.

Such check is fine, but would be better placed in __alloc_extent_buffer,
not each time we access the eb.

Re: [PATCH 1/3] btrfs: simplify counting number of eb pages

[Qu Wenruo]

On 2018年04月24日 18:29, David Sterba wrote:
> On Tue, Apr 24, 2018 at 02:22:15PM +0800, Qu Wenruo wrote:
>>
>>
>> On 2018年04月24日 13:59, Nikolay Borisov wrote:
>>>
>>>
>>> On 24.04.2018 02:03, David Sterba wrote:
>>>> The eb length is nodesize, as initialized in __alloc_extent_buffer.
>>>> Regardless of start, we should always get the same number of pages, so
>>>> use that fact.
>>>>
>>>> Signed-off-by: David Sterba <dsterba@suse.com>
>>>> ---
>>>>  fs/btrfs/extent_io.h | 3 +--
>>>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
>>>> index a53009694b16..ee92c1289edd 100644
>>>> --- a/fs/btrfs/extent_io.h
>>>> +++ b/fs/btrfs/extent_io.h
>>>> @@ -454,8 +454,7 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
>>>>  
>>>>  static inline unsigned long num_extent_pages(u64 start, u64 len)
>>>>  {
>>>> -	return ((start + len + PAGE_SIZE - 1) >> PAGE_SHIFT) -
>>>> -		(start >> PAGE_SHIFT);
>>>> +	return len >> PAGE_SHIFT;
>>>
>>> Shouldn't this really be len + PAGE_SIZE -1 or in fact DIV_ROUND_DOWN
>>> (len, PAGE_SIZE). Because with a nodesize of 4k (and basically less than
>>> a page size) we can get into a situation where we do:
>>>
>>> 4096 >> 13 =
>>>
>>> On powerpc for example we have:
>>>
>>> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              18
>>> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              16
>>> arch/powerpc/include/asm/page.h:#define PAGE_SHIFT              14
>>
>> For such case, the fs won't be mounted as we don't have sub-pagesized
>> nodesize support yet.
>> So won't hit the problem.
>>
>> Although a WARN_ON(len < PAGE_SIZE || IS_ALIGNED(start, PAGE_SIZE))
>> would do no harm here.
> 
> Such check is fine, but would be better placed in __alloc_extent_buffer,
> not each time we access the eb.

Yep, makes more sense than my initial idea.

Thanks,
Qu

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> 

[PATCH 2/3] btrfs: pass only eb to num_extent_pages

[David Sterba]

Almost all callers pass the start and len as 2 arguments but this is not
necessary, all the information is provided by the eb. By reordering the
calls to num_extent_pages, we don't need the local variables with
start/len.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/extent_io.c | 30 +++++++++++++++---------------
 fs/btrfs/extent_io.h |  4 ++--
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index fb32394fd830..0cc5d6ae1876 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2062,7 +2062,7 @@ int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
 			 struct extent_buffer *eb, int mirror_num)
 {
 	u64 start = eb->start;
-	unsigned long i, num_pages = num_extent_pages(eb->start, eb->len);
+	unsigned long i, num_pages = num_extent_pages(eb);
 	int ret = 0;
 
 	if (sb_rdonly(fs_info->sb))
@@ -3591,7 +3591,7 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 	if (!ret)
 		return ret;
 
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
 		struct page *p = eb->pages[i];
 
@@ -3721,7 +3721,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
 	int ret = 0;
 
 	clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags);
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	atomic_set(&eb->io_pages, num_pages);
 
 	/* set btree blocks beyond nritems with 0 to avoid stale content. */
@@ -4654,7 +4654,7 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
 
 	BUG_ON(extent_buffer_under_io(eb));
 
-	index = num_extent_pages(eb->start, eb->len);
+	index = num_extent_pages(eb);
 	if (index == 0)
 		return;
 
@@ -4747,7 +4747,7 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
 	unsigned long i;
 	struct page *p;
 	struct extent_buffer *new;
-	unsigned long num_pages = num_extent_pages(src->start, src->len);
+	unsigned long num_pages = num_extent_pages(src);
 
 	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
 	if (new == NULL)
@@ -4779,12 +4779,11 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 	unsigned long num_pages;
 	unsigned long i;
 
-	num_pages = num_extent_pages(start, len);
-
 	eb = __alloc_extent_buffer(fs_info, start, len);
 	if (!eb)
 		return NULL;
 
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
 		eb->pages[i] = alloc_page(GFP_NOFS);
 		if (!eb->pages[i])
@@ -4848,7 +4847,7 @@ static void mark_extent_buffer_accessed(struct extent_buffer *eb,
 
 	check_buffer_tree_ref(eb);
 
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
 		struct page *p = eb->pages[i];
 
@@ -4945,7 +4944,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 					  u64 start)
 {
 	unsigned long len = fs_info->nodesize;
-	unsigned long num_pages = num_extent_pages(start, len);
+	unsigned long num_pages;
 	unsigned long i;
 	unsigned long index = start >> PAGE_SHIFT;
 	struct extent_buffer *eb;
@@ -4968,6 +4967,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 	if (!eb)
 		return ERR_PTR(-ENOMEM);
 
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++, index++) {
 		p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
 		if (!p) {
@@ -5164,7 +5164,7 @@ void clear_extent_buffer_dirty(struct extent_buffer *eb)
 	unsigned long num_pages;
 	struct page *page;
 
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 
 	for (i = 0; i < num_pages; i++) {
 		page = eb->pages[i];
@@ -5198,7 +5198,7 @@ int set_extent_buffer_dirty(struct extent_buffer *eb)
 
 	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
 
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	WARN_ON(atomic_read(&eb->refs) == 0);
 	WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
 
@@ -5214,7 +5214,7 @@ void clear_extent_buffer_uptodate(struct extent_buffer *eb)
 	unsigned long num_pages;
 
 	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
 		page = eb->pages[i];
 		if (page)
@@ -5229,7 +5229,7 @@ void set_extent_buffer_uptodate(struct extent_buffer *eb)
 	unsigned long num_pages;
 
 	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
 		page = eb->pages[i];
 		SetPageUptodate(page);
@@ -5253,7 +5253,7 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
 	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
 		return 0;
 
-	num_pages = num_extent_pages(eb->start, eb->len);
+	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
 		page = eb->pages[i];
 		if (wait == WAIT_NONE) {
@@ -5581,7 +5581,7 @@ void copy_extent_buffer_full(struct extent_buffer *dst,
 
 	ASSERT(dst->len == src->len);
 
-	num_pages = num_extent_pages(dst->start, dst->len);
+	num_pages = num_extent_pages(dst);
 	for (i = 0; i < num_pages; i++)
 		copy_page(page_address(dst->pages[i]),
 				page_address(src->pages[i]));
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index ee92c1289edd..d08abc9d385e 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -452,9 +452,9 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
 			     int mirror_num);
 void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
 
-static inline unsigned long num_extent_pages(u64 start, u64 len)
+static inline unsigned long num_extent_pages(const struct extent_buffer *eb)
 {
-	return len >> PAGE_SHIFT;
+	return eb->len >> PAGE_SHIFT;
 }
 
 static inline void extent_buffer_get(struct extent_buffer *eb)
-- 
2.16.2

Re: [PATCH 2/3] btrfs: pass only eb to num_extent_pages

[Nikolay Borisov]

On 24.04.2018 02:03, David Sterba wrote:
> Almost all callers pass the start and len as 2 arguments but this is not
> necessary, all the information is provided by the eb. By reordering the
> calls to num_extent_pages, we don't need the local variables with
> start/len.
> 
> Signed-off-by: David Sterba <dsterba@suse.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/extent_io.c | 30 +++++++++++++++---------------
>  fs/btrfs/extent_io.h |  4 ++--
>  2 files changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index fb32394fd830..0cc5d6ae1876 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2062,7 +2062,7 @@ int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
>  			 struct extent_buffer *eb, int mirror_num)
>  {
>  	u64 start = eb->start;
> -	unsigned long i, num_pages = num_extent_pages(eb->start, eb->len);
> +	unsigned long i, num_pages = num_extent_pages(eb);
>  	int ret = 0;
>  
>  	if (sb_rdonly(fs_info->sb))
> @@ -3591,7 +3591,7 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
>  	if (!ret)
>  		return ret;
>  
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++) {
>  		struct page *p = eb->pages[i];
>  
> @@ -3721,7 +3721,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
>  	int ret = 0;
>  
>  	clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags);
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	atomic_set(&eb->io_pages, num_pages);
>  
>  	/* set btree blocks beyond nritems with 0 to avoid stale content. */
> @@ -4654,7 +4654,7 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
>  
>  	BUG_ON(extent_buffer_under_io(eb));
>  
> -	index = num_extent_pages(eb->start, eb->len);
> +	index = num_extent_pages(eb);
>  	if (index == 0)
>  		return;
>  
> @@ -4747,7 +4747,7 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
>  	unsigned long i;
>  	struct page *p;
>  	struct extent_buffer *new;
> -	unsigned long num_pages = num_extent_pages(src->start, src->len);
> +	unsigned long num_pages = num_extent_pages(src);
>  
>  	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
>  	if (new == NULL)
> @@ -4779,12 +4779,11 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
>  	unsigned long num_pages;
>  	unsigned long i;
>  
> -	num_pages = num_extent_pages(start, len);
> -
>  	eb = __alloc_extent_buffer(fs_info, start, len);
>  	if (!eb)
>  		return NULL;
>  
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++) {
>  		eb->pages[i] = alloc_page(GFP_NOFS);
>  		if (!eb->pages[i])
> @@ -4848,7 +4847,7 @@ static void mark_extent_buffer_accessed(struct extent_buffer *eb,
>  
>  	check_buffer_tree_ref(eb);
>  
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++) {
>  		struct page *p = eb->pages[i];
>  
> @@ -4945,7 +4944,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
>  					  u64 start)
>  {
>  	unsigned long len = fs_info->nodesize;
> -	unsigned long num_pages = num_extent_pages(start, len);
> +	unsigned long num_pages;
>  	unsigned long i;
>  	unsigned long index = start >> PAGE_SHIFT;
>  	struct extent_buffer *eb;
> @@ -4968,6 +4967,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
>  	if (!eb)
>  		return ERR_PTR(-ENOMEM);
>  
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++, index++) {
>  		p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
>  		if (!p) {
> @@ -5164,7 +5164,7 @@ void clear_extent_buffer_dirty(struct extent_buffer *eb)
>  	unsigned long num_pages;
>  	struct page *page;
>  
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  
>  	for (i = 0; i < num_pages; i++) {
>  		page = eb->pages[i];
> @@ -5198,7 +5198,7 @@ int set_extent_buffer_dirty(struct extent_buffer *eb)
>  
>  	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
>  
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	WARN_ON(atomic_read(&eb->refs) == 0);
>  	WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
>  
> @@ -5214,7 +5214,7 @@ void clear_extent_buffer_uptodate(struct extent_buffer *eb)
>  	unsigned long num_pages;
>  
>  	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++) {
>  		page = eb->pages[i];
>  		if (page)
> @@ -5229,7 +5229,7 @@ void set_extent_buffer_uptodate(struct extent_buffer *eb)
>  	unsigned long num_pages;
>  
>  	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++) {
>  		page = eb->pages[i];
>  		SetPageUptodate(page);
> @@ -5253,7 +5253,7 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
>  	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
>  		return 0;
>  
> -	num_pages = num_extent_pages(eb->start, eb->len);
> +	num_pages = num_extent_pages(eb);
>  	for (i = 0; i < num_pages; i++) {
>  		page = eb->pages[i];
>  		if (wait == WAIT_NONE) {
> @@ -5581,7 +5581,7 @@ void copy_extent_buffer_full(struct extent_buffer *dst,
>  
>  	ASSERT(dst->len == src->len);
>  
> -	num_pages = num_extent_pages(dst->start, dst->len);
> +	num_pages = num_extent_pages(dst);
>  	for (i = 0; i < num_pages; i++)
>  		copy_page(page_address(dst->pages[i]),
>  				page_address(src->pages[i]));
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index ee92c1289edd..d08abc9d385e 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -452,9 +452,9 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
>  			     int mirror_num);
>  void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
>  
> -static inline unsigned long num_extent_pages(u64 start, u64 len)
> +static inline unsigned long num_extent_pages(const struct extent_buffer *eb)
>  {
> -	return len >> PAGE_SHIFT;
> +	return eb->len >> PAGE_SHIFT;
>  }
>  
>  static inline void extent_buffer_get(struct extent_buffer *eb)
> 

[PATCH 3/3] btrfs: switch types to int when counting eb pages

[David Sterba]

The loops iterating eb pages use unsigned long, that's an overkill as
we know that there are at most 16 pages (64k / 4k), and 4 by default
(with nodesize 16k).

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/extent_io.c | 44 ++++++++++++++++++++++----------------------
 fs/btrfs/extent_io.h |  2 +-
 2 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0cc5d6ae1876..5bdfdb9c8777 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2062,7 +2062,7 @@ int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
 			 struct extent_buffer *eb, int mirror_num)
 {
 	u64 start = eb->start;
-	unsigned long i, num_pages = num_extent_pages(eb);
+	int i, num_pages = num_extent_pages(eb);
 	int ret = 0;
 
 	if (sb_rdonly(fs_info->sb))
@@ -3541,7 +3541,7 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 			  struct btrfs_fs_info *fs_info,
 			  struct extent_page_data *epd)
 {
-	unsigned long i, num_pages;
+	int i, num_pages;
 	int flush = 0;
 	int ret = 0;
 
@@ -3715,7 +3715,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
 	struct extent_io_tree *tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
 	u64 offset = eb->start;
 	u32 nritems;
-	unsigned long i, num_pages;
+	int i, num_pages;
 	unsigned long start, end;
 	unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META;
 	int ret = 0;
@@ -4648,7 +4648,7 @@ int extent_buffer_under_io(struct extent_buffer *eb)
  */
 static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
 {
-	unsigned long index;
+	int index;
 	struct page *page;
 	int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
 
@@ -4744,10 +4744,10 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 
 struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
 {
-	unsigned long i;
+	int i;
 	struct page *p;
 	struct extent_buffer *new;
-	unsigned long num_pages = num_extent_pages(src);
+	int num_pages = num_extent_pages(src);
 
 	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
 	if (new == NULL)
@@ -4776,8 +4776,8 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 						  u64 start, unsigned long len)
 {
 	struct extent_buffer *eb;
-	unsigned long num_pages;
-	unsigned long i;
+	int num_pages;
+	int i;
 
 	eb = __alloc_extent_buffer(fs_info, start, len);
 	if (!eb)
@@ -4843,7 +4843,7 @@ static void check_buffer_tree_ref(struct extent_buffer *eb)
 static void mark_extent_buffer_accessed(struct extent_buffer *eb,
 		struct page *accessed)
 {
-	unsigned long num_pages, i;
+	int num_pages, i;
 
 	check_buffer_tree_ref(eb);
 
@@ -4944,8 +4944,8 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 					  u64 start)
 {
 	unsigned long len = fs_info->nodesize;
-	unsigned long num_pages;
-	unsigned long i;
+	int num_pages;
+	int i;
 	unsigned long index = start >> PAGE_SHIFT;
 	struct extent_buffer *eb;
 	struct extent_buffer *exists = NULL;
@@ -5160,8 +5160,8 @@ void free_extent_buffer_stale(struct extent_buffer *eb)
 
 void clear_extent_buffer_dirty(struct extent_buffer *eb)
 {
-	unsigned long i;
-	unsigned long num_pages;
+	int i;
+	int num_pages;
 	struct page *page;
 
 	num_pages = num_extent_pages(eb);
@@ -5190,8 +5190,8 @@ void clear_extent_buffer_dirty(struct extent_buffer *eb)
 
 int set_extent_buffer_dirty(struct extent_buffer *eb)
 {
-	unsigned long i;
-	unsigned long num_pages;
+	int i;
+	int num_pages;
 	int was_dirty = 0;
 
 	check_buffer_tree_ref(eb);
@@ -5209,9 +5209,9 @@ int set_extent_buffer_dirty(struct extent_buffer *eb)
 
 void clear_extent_buffer_uptodate(struct extent_buffer *eb)
 {
-	unsigned long i;
+	int i;
 	struct page *page;
-	unsigned long num_pages;
+	int num_pages;
 
 	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
 	num_pages = num_extent_pages(eb);
@@ -5224,9 +5224,9 @@ void clear_extent_buffer_uptodate(struct extent_buffer *eb)
 
 void set_extent_buffer_uptodate(struct extent_buffer *eb)
 {
-	unsigned long i;
+	int i;
 	struct page *page;
-	unsigned long num_pages;
+	int num_pages;
 
 	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
 	num_pages = num_extent_pages(eb);
@@ -5239,13 +5239,13 @@ void set_extent_buffer_uptodate(struct extent_buffer *eb)
 int read_extent_buffer_pages(struct extent_io_tree *tree,
 			     struct extent_buffer *eb, int wait, int mirror_num)
 {
-	unsigned long i;
+	int i;
 	struct page *page;
 	int err;
 	int ret = 0;
 	int locked_pages = 0;
 	int all_uptodate = 1;
-	unsigned long num_pages;
+	int num_pages;
 	unsigned long num_reads = 0;
 	struct bio *bio = NULL;
 	unsigned long bio_flags = 0;
@@ -5577,7 +5577,7 @@ void copy_extent_buffer_full(struct extent_buffer *dst,
 			     struct extent_buffer *src)
 {
 	int i;
-	unsigned num_pages;
+	int num_pages;
 
 	ASSERT(dst->len == src->len);
 
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index d08abc9d385e..3248553a3aa2 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -452,7 +452,7 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
 			     int mirror_num);
 void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
 
-static inline unsigned long num_extent_pages(const struct extent_buffer *eb)
+static inline int num_extent_pages(const struct extent_buffer *eb)
 {
 	return eb->len >> PAGE_SHIFT;
 }
-- 
2.16.2

Re: [PATCH 3/3] btrfs: switch types to int when counting eb pages

[Nikolay Borisov]

On 24.04.2018 02:03, David Sterba wrote:
> The loops iterating eb pages use unsigned long, that's an overkill as
> we know that there are at most 16 pages (64k / 4k), and 4 by default
> (with nodesize 16k).
> 
> Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/extent_io.c | 44 ++++++++++++++++++++++----------------------
>  fs/btrfs/extent_io.h |  2 +-
>  2 files changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 0cc5d6ae1876..5bdfdb9c8777 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2062,7 +2062,7 @@ int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
>  			 struct extent_buffer *eb, int mirror_num)
>  {
>  	u64 start = eb->start;
> -	unsigned long i, num_pages = num_extent_pages(eb);
> +	int i, num_pages = num_extent_pages(eb);
>  	int ret = 0;
>  
>  	if (sb_rdonly(fs_info->sb))
> @@ -3541,7 +3541,7 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
>  			  struct btrfs_fs_info *fs_info,
>  			  struct extent_page_data *epd)
>  {
> -	unsigned long i, num_pages;
> +	int i, num_pages;
>  	int flush = 0;
>  	int ret = 0;
>  
> @@ -3715,7 +3715,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
>  	struct extent_io_tree *tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
>  	u64 offset = eb->start;
>  	u32 nritems;
> -	unsigned long i, num_pages;
> +	int i, num_pages;
>  	unsigned long start, end;
>  	unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META;
>  	int ret = 0;
> @@ -4648,7 +4648,7 @@ int extent_buffer_under_io(struct extent_buffer *eb)
>   */
>  static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
>  {
> -	unsigned long index;
> +	int index;
>  	struct page *page;
>  	int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
>  
> @@ -4744,10 +4744,10 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
>  
>  struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
>  {
> -	unsigned long i;
> +	int i;
>  	struct page *p;
>  	struct extent_buffer *new;
> -	unsigned long num_pages = num_extent_pages(src);
> +	int num_pages = num_extent_pages(src);
>  
>  	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
>  	if (new == NULL)
> @@ -4776,8 +4776,8 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
>  						  u64 start, unsigned long len)
>  {
>  	struct extent_buffer *eb;
> -	unsigned long num_pages;
> -	unsigned long i;
> +	int num_pages;
> +	int i;
>  
>  	eb = __alloc_extent_buffer(fs_info, start, len);
>  	if (!eb)
> @@ -4843,7 +4843,7 @@ static void check_buffer_tree_ref(struct extent_buffer *eb)
>  static void mark_extent_buffer_accessed(struct extent_buffer *eb,
>  		struct page *accessed)
>  {
> -	unsigned long num_pages, i;
> +	int num_pages, i;
>  
>  	check_buffer_tree_ref(eb);
>  
> @@ -4944,8 +4944,8 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
>  					  u64 start)
>  {
>  	unsigned long len = fs_info->nodesize;
> -	unsigned long num_pages;
> -	unsigned long i;
> +	int num_pages;
> +	int i;
>  	unsigned long index = start >> PAGE_SHIFT;
>  	struct extent_buffer *eb;
>  	struct extent_buffer *exists = NULL;
> @@ -5160,8 +5160,8 @@ void free_extent_buffer_stale(struct extent_buffer *eb)
>  
>  void clear_extent_buffer_dirty(struct extent_buffer *eb)
>  {
> -	unsigned long i;
> -	unsigned long num_pages;
> +	int i;
> +	int num_pages;
>  	struct page *page;
>  
>  	num_pages = num_extent_pages(eb);
> @@ -5190,8 +5190,8 @@ void clear_extent_buffer_dirty(struct extent_buffer *eb)
>  
>  int set_extent_buffer_dirty(struct extent_buffer *eb)
>  {
> -	unsigned long i;
> -	unsigned long num_pages;
> +	int i;
> +	int num_pages;
>  	int was_dirty = 0;
>  
>  	check_buffer_tree_ref(eb);
> @@ -5209,9 +5209,9 @@ int set_extent_buffer_dirty(struct extent_buffer *eb)
>  
>  void clear_extent_buffer_uptodate(struct extent_buffer *eb)
>  {
> -	unsigned long i;
> +	int i;
>  	struct page *page;
> -	unsigned long num_pages;
> +	int num_pages;
>  
>  	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
>  	num_pages = num_extent_pages(eb);
> @@ -5224,9 +5224,9 @@ void clear_extent_buffer_uptodate(struct extent_buffer *eb)
>  
>  void set_extent_buffer_uptodate(struct extent_buffer *eb)
>  {
> -	unsigned long i;
> +	int i;
>  	struct page *page;
> -	unsigned long num_pages;
> +	int num_pages;
>  
>  	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
>  	num_pages = num_extent_pages(eb);
> @@ -5239,13 +5239,13 @@ void set_extent_buffer_uptodate(struct extent_buffer *eb)
>  int read_extent_buffer_pages(struct extent_io_tree *tree,
>  			     struct extent_buffer *eb, int wait, int mirror_num)
>  {
> -	unsigned long i;
> +	int i;
>  	struct page *page;
>  	int err;
>  	int ret = 0;
>  	int locked_pages = 0;
>  	int all_uptodate = 1;
> -	unsigned long num_pages;
> +	int num_pages;
>  	unsigned long num_reads = 0;
>  	struct bio *bio = NULL;
>  	unsigned long bio_flags = 0;
> @@ -5577,7 +5577,7 @@ void copy_extent_buffer_full(struct extent_buffer *dst,
>  			     struct extent_buffer *src)
>  {
>  	int i;
> -	unsigned num_pages;
> +	int num_pages;
>  
>  	ASSERT(dst->len == src->len);
>  
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index d08abc9d385e..3248553a3aa2 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -452,7 +452,7 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
>  			     int mirror_num);
>  void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
>  
> -static inline unsigned long num_extent_pages(const struct extent_buffer *eb)
> +static inline int num_extent_pages(const struct extent_buffer *eb)
>  {
>  	return eb->len >> PAGE_SHIFT;
>  }
>