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Subject[PATCH] fs: buffer: Modify alloc_page_buffers.
Date
Make alloc_page_buffers support circular buffer list and initialise
b_state field.
Optimize the performance by removing the buffer list traversal to create
circular buffer list.

Signed-off-by: Sean Fu <fxinrong@gmail.com>
---
drivers/md/bitmap.c | 2 +-
fs/buffer.c | 37 +++++++++++++++----------------------
fs/ntfs/aops.c | 2 +-
fs/ntfs/mft.c | 2 +-
include/linux/buffer_head.h | 2 +-
5 files changed, 19 insertions(+), 26 deletions(-)

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index f4eace5..615a46e 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -367,7 +367,7 @@ static int read_page(struct file *file, unsigned long index,
pr_debug("read bitmap file (%dB @ %llu)\n", (int)PAGE_SIZE,
(unsigned long long)index << PAGE_SHIFT);

- bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0);
+ bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0, 0, 0);
if (!bh) {
ret = -ENOMEM;
goto out;
diff --git a/fs/buffer.c b/fs/buffer.c
index 161be58..8111eca 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -864,9 +864,9 @@ int remove_inode_buffers(struct inode *inode)
* which may not fail from ordinary buffer allocations.
*/
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
- int retry)
+ int retry, int circular, unsigned long b_state)
{
- struct buffer_head *bh, *head;
+ struct buffer_head *bh, *head, *tail;
long offset;

try_again:
@@ -879,13 +879,21 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,

bh->b_this_page = head;
bh->b_blocknr = -1;
- head = bh;

+ if (head == NULL)
+ tail = bh;
+
+ head = bh;
+ bh->b_state = b_state;
bh->b_size = size;

/* Link the buffer to its page */
set_bh_page(bh, page, offset);
}
+
+ if (circular)
+ tail->b_this_page = head;
+
return head;
/*
* In case anything failed, we just free everything we got.
@@ -922,14 +930,6 @@ EXPORT_SYMBOL_GPL(alloc_page_buffers);
static inline void
link_dev_buffers(struct page *page, struct buffer_head *head)
{
- struct buffer_head *bh, *tail;
-
- bh = head;
- do {
- tail = bh;
- bh = bh->b_this_page;
- } while (bh);
- tail->b_this_page = head;
attach_page_buffers(page, head);
}

@@ -1024,7 +1024,7 @@ grow_dev_page(struct block_device *bdev, sector_t block,
/*
* Allocate some buffers for this page
*/
- bh = alloc_page_buffers(page, size, 0);
+ bh = alloc_page_buffers(page, size, 0, 1, 0);
if (!bh)
goto failed;

@@ -1578,16 +1578,9 @@ EXPORT_SYMBOL(block_invalidatepage);
void create_empty_buffers(struct page *page,
unsigned long blocksize, unsigned long b_state)
{
- struct buffer_head *bh, *head, *tail;
+ struct buffer_head *bh, *head;

- head = alloc_page_buffers(page, blocksize, 1);
- bh = head;
- do {
- bh->b_state |= b_state;
- tail = bh;
- bh = bh->b_this_page;
- } while (bh);
- tail->b_this_page = head;
+ head = alloc_page_buffers(page, blocksize, 1, 1, b_state);

spin_lock(&page->mapping->private_lock);
if (PageUptodate(page) || PageDirty(page)) {
@@ -2642,7 +2635,7 @@ int nobh_write_begin(struct address_space *mapping,
* Be careful: the buffer linked list is a NULL terminated one, rather
* than the circular one we're used to.
*/
- head = alloc_page_buffers(page, blocksize, 0);
+ head = alloc_page_buffers(page, blocksize, 0, 0, 0);
if (!head) {
ret = -ENOMEM;
goto out_release;
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index cc91856..e692142 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -1739,7 +1739,7 @@ void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs) {
spin_lock(&mapping->private_lock);
if (unlikely(!page_has_buffers(page))) {
spin_unlock(&mapping->private_lock);
- bh = head = alloc_page_buffers(page, bh_size, 1);
+ bh = head = alloc_page_buffers(page, bh_size, 1, 0, 0);
spin_lock(&mapping->private_lock);
if (likely(!page_has_buffers(page))) {
struct buffer_head *tail;
diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
index b6f4021..175a02b 100644
--- a/fs/ntfs/mft.c
+++ b/fs/ntfs/mft.c
@@ -507,7 +507,7 @@ int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no,
if (unlikely(!page_has_buffers(page))) {
struct buffer_head *tail;

- bh = head = alloc_page_buffers(page, blocksize, 1);
+ bh = head = alloc_page_buffers(page, blocksize, 1, 0, 0);
do {
set_buffer_uptodate(bh);
tail = bh;
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index bd029e52..9a29826 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -155,7 +155,7 @@ void set_bh_page(struct buffer_head *bh,
struct page *page, unsigned long offset);
int try_to_free_buffers(struct page *);
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
- int retry);
+ int retry, int circular, unsigned long b_state);
void create_empty_buffers(struct page *, unsigned long,
unsigned long b_state);
void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
--
2.6.2
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