Re: [PATCH 2/2] Btrfs: use helper to simplify lock/unlock pages

[David Sterba]

On Thu, Feb 02, 2017 at 05:49:23PM -0800, Liu Bo wrote:
> Since we have a helper to set page bits, let lock_delalloc_pages and
> __unlock_for_delalloc use it.
> 
> Signed-off-by: Liu Bo 

Reviewed-by: David Sterba 

I've separated the changes of __process_pages_contig to another patch,
just moving hunks.
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[PATCH 2/2] Btrfs: use helper to simplify lock/unlock pages

[Liu Bo]

Since we have a helper to set page bits, let lock_delalloc_pages and
__unlock_for_delalloc use it.

Signed-off-by: Liu Bo 
---
 fs/btrfs/extent_io.c | 122 ++-
 fs/btrfs/extent_io.h |   3 +-
 2 files changed, 54 insertions(+), 71 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2ef2d05..7e9639f 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1549,33 +1549,24 @@ static noinline u64 find_delalloc_range(struct 
extent_io_tree *tree,
return found;
 }
 
+static int __process_pages_contig(struct address_space *mapping,
+ struct page *locked_page,
+ pgoff_t start_index, pgoff_t end_index,
+ unsigned long page_ops, pgoff_t *index_ret);
+
 static noinline void __unlock_for_delalloc(struct inode *inode,
   struct page *locked_page,
   u64 start, u64 end)
 {
-   int ret;
-   struct page *pages[16];
unsigned long index = start >> PAGE_SHIFT;
unsigned long end_index = end >> PAGE_SHIFT;
-   unsigned long nr_pages = end_index - index + 1;
-   int i;
 
+   ASSERT(locked_page);
if (index == locked_page->index && end_index == index)
return;
 
-   while (nr_pages > 0) {
-   ret = find_get_pages_contig(inode->i_mapping, index,
-min_t(unsigned long, nr_pages,
-ARRAY_SIZE(pages)), pages);
-   for (i = 0; i < ret; i++) {
-   if (pages[i] != locked_page)
-   unlock_page(pages[i]);
-   put_page(pages[i]);
-   }
-   nr_pages -= ret;
-   index += ret;
-   cond_resched();
-   }
+   __process_pages_contig(inode->i_mapping, locked_page, index, end_index,
+  PAGE_UNLOCK, NULL);
 }
 
 static noinline int lock_delalloc_pages(struct inode *inode,
@@ -1584,59 +1575,19 @@ static noinline int lock_delalloc_pages(struct inode 
*inode,
u64 delalloc_end)
 {
unsigned long index = delalloc_start >> PAGE_SHIFT;
-   unsigned long start_index = index;
+   unsigned long index_ret = index;
unsigned long end_index = delalloc_end >> PAGE_SHIFT;
-   unsigned long pages_locked = 0;
-   struct page *pages[16];
-   unsigned long nrpages;
int ret;
-   int i;
 
-   /* the caller is responsible for locking the start index */
+   ASSERT(locked_page);
if (index == locked_page->index && index == end_index)
return 0;
 
-   /* skip the page at the start index */
-   nrpages = end_index - index + 1;
-   while (nrpages > 0) {
-   ret = find_get_pages_contig(inode->i_mapping, index,
-min_t(unsigned long,
-nrpages, ARRAY_SIZE(pages)), pages);
-   if (ret == 0) {
-   ret = -EAGAIN;
-   goto done;
-   }
-   /* now we have an array of pages, lock them all */
-   for (i = 0; i < ret; i++) {
-   /*
-* the caller is taking responsibility for
-* locked_page
-*/
-   if (pages[i] != locked_page) {
-   lock_page(pages[i]);
-   if (!PageDirty(pages[i]) ||
-   pages[i]->mapping != inode->i_mapping) {
-   ret = -EAGAIN;
-   unlock_page(pages[i]);
-   put_page(pages[i]);
-   goto done;
-   }
-   }
-   put_page(pages[i]);
-   pages_locked++;
-   }
-   nrpages -= ret;
-   index += ret;
-   cond_resched();
-   }
-   ret = 0;
-done:
-   if (ret && pages_locked) {
-   __unlock_for_delalloc(inode, locked_page,
- delalloc_start,
- ((u64)(start_index + pages_locked - 1)) <<
- PAGE_SHIFT);
-   }
+   ret = __process_pages_contig(inode->i_mapping, locked_page, index,
+end_index, PAGE_LOCK, &index_ret);
+   if (ret == -EAGAIN)
+   __unlock_for_delalloc(inode, locked_page, delalloc_start,
+ (u64)index_ret << PAGE_SHIFT);
return ret;
 }
 
@@ -1726,17 +1677,24 @@ STATIC u64 find_lock_delalloc_range(struct inode *inode,
return found;
 }