1.Create circular buffer list in alloc_page_buffers.
Remove unnecessary traversal in link_dev_buffers to create circular buffer list.
Make nobh_write_begin and nobh_write_end to support circular buffer list.
2.fs/ntfs: Make ntfs to support circular buffer list.
3.md: bitmap: Support circular buffer list.
Modify write_page free_buffers and read_page to support circular buffer list.
Sean Fu (3):
fs: buffer: Create circular buffer list for pages.
fs/ntfs: Make ntfs to support circular buffer list.
md: bitmap: Support circular buffer list.
drivers/md/md-bitmap.c | 36 +++++++++++++++++++-----------------
fs/buffer.c | 48 +++++++++++++++++++++---------------------------
fs/ntfs/aops.c | 6 ++----
fs/ntfs/mft.c | 4 ----
4 files changed, 42 insertions(+), 52 deletions(-)
--
2.6.2
Make alloc_page_buffers to create circular buffer list instead linear
list.
Remove unnecessary traversal in link_dev_buffers to create circular
buffer list.
Make nobh_write_begin and nobh_write_end to support circular buffer list
traversal.
Signed-off-by: Sean Fu <[email protected]>
---
fs/buffer.c | 48 +++++++++++++++++++++---------------------------
1 file changed, 21 insertions(+), 27 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 0736a6a..7e62c75 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -842,29 +842,36 @@ int remove_inode_buffers(struct inode *inode)
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
bool retry)
{
- struct buffer_head *bh, *head;
+ struct buffer_head *bh, *head, *tail;
gfp_t gfp = GFP_NOFS;
long offset;
if (retry)
gfp |= __GFP_NOFAIL;
- head = NULL;
+ head = tail = NULL;
offset = PAGE_SIZE;
while ((offset -= size) >= 0) {
bh = alloc_buffer_head(gfp);
if (!bh)
goto no_grow;
- bh->b_this_page = head;
+ if (unlikely(!head))
+ tail = bh;
+ else
+ bh->b_this_page = head;
+
bh->b_blocknr = -1;
head = bh;
-
bh->b_size = size;
/* Link the buffer to its page */
set_bh_page(bh, page, offset);
}
+
+ if (tail)
+ tail->b_this_page = head;
+
return head;
/*
* In case anything failed, we just free everything we got.
@@ -882,20 +889,6 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
}
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);
-}
-
static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
{
sector_t retval = ~((sector_t)0);
@@ -993,7 +986,7 @@ grow_dev_page(struct block_device *bdev, sector_t block,
* run under the page lock.
*/
spin_lock(&inode->i_mapping->private_lock);
- link_dev_buffers(page, bh);
+ attach_page_buffers(page, bh);
end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
size);
spin_unlock(&inode->i_mapping->private_lock);
@@ -1533,16 +1526,14 @@ 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, true);
bh = head;
do {
bh->b_state |= b_state;
- tail = bh;
bh = bh->b_this_page;
- } while (bh);
- tail->b_this_page = head;
+ } while (bh != head);
spin_lock(&page->mapping->private_lock);
if (PageUptodate(page) || PageDirty(page)) {
@@ -2655,11 +2646,14 @@ int nobh_write_begin(struct address_space *mapping,
* any VM or truncate activity. Hence we don't need to care
* for the buffer_head refcounts.
*/
- for (bh = head; bh; bh = bh->b_this_page) {
+ bh = head;
+ do {
wait_on_buffer(bh);
if (!buffer_uptodate(bh))
ret = -EIO;
- }
+ bh = bh->b_this_page;
+ } while (bh != head);
+
if (ret)
goto failed;
}
@@ -2717,11 +2711,11 @@ int nobh_write_end(struct file *file, struct address_space *mapping,
unlock_page(page);
put_page(page);
- while (head) {
+ do {
bh = head;
head = head->b_this_page;
free_buffer_head(bh);
- }
+ } while (head != fsdata);
return copied;
}
--
2.6.2
Modify mark_ntfs_record_dirty to support circular buffer list.
alloc_page_buffers created circular buffer list. So the circular list
linking in ntfs_sync_mft_mirror is unnecessary.
Signed-off-by: Sean Fu <[email protected]>
---
fs/ntfs/aops.c | 6 ++----
fs/ntfs/mft.c | 4 ----
2 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 3a2e509..4e69577 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -1746,10 +1746,8 @@ void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs) {
do {
set_buffer_uptodate(bh);
- tail = bh;
bh = bh->b_this_page;
- } while (bh);
- tail->b_this_page = head;
+ } while (bh != head);
attach_page_buffers(page, head);
} else
buffers_to_free = bh;
@@ -1771,7 +1769,7 @@ void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs) {
bh = buffers_to_free->b_this_page;
free_buffer_head(buffers_to_free);
buffers_to_free = bh;
- } while (buffers_to_free);
+ } while (buffers_to_free != head);
}
}
diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
index ee8392a..26ba4f6 100644
--- a/fs/ntfs/mft.c
+++ b/fs/ntfs/mft.c
@@ -505,15 +505,11 @@ int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no,
memcpy(kmirr, m, vol->mft_record_size);
/* Create uptodate buffers if not present. */
if (unlikely(!page_has_buffers(page))) {
- struct buffer_head *tail;
-
bh = head = alloc_page_buffers(page, blocksize, true);
do {
set_buffer_uptodate(bh);
- tail = bh;
bh = bh->b_this_page;
} while (bh);
- tail->b_this_page = head;
attach_page_buffers(page, head);
}
bh = head = page_buffers(page);
--
2.6.2
Modify write_page free_buffers and read_page to support circular buffer
list.
Signed-off-by: Sean Fu <[email protected]>
---
drivers/md/md-bitmap.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 239c7bb..b8412c2 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -286,7 +286,7 @@ static void bitmap_file_kick(struct bitmap *bitmap);
*/
static void write_page(struct bitmap *bitmap, struct page *page, int wait)
{
- struct buffer_head *bh;
+ struct buffer_head *bh, *head;
if (bitmap->storage.file == NULL) {
switch (write_sb_page(bitmap, page, wait)) {
@@ -295,15 +295,16 @@ static void write_page(struct bitmap *bitmap, struct page *page, int wait)
}
} else {
- bh = page_buffers(page);
+ bh = head = page_buffers(page);
- while (bh && bh->b_blocknr) {
- atomic_inc(&bitmap->pending_writes);
- set_buffer_locked(bh);
- set_buffer_mapped(bh);
- submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
- bh = bh->b_this_page;
- }
+ do {
+ if (bh && bh->b_blocknr) {
+ atomic_inc(&bitmap->pending_writes);
+ set_buffer_locked(bh);
+ set_buffer_mapped(bh);
+ submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
+ }
+ } while ((bh = bh->b_this_page) != head);
if (wait)
wait_event(bitmap->write_wait,
@@ -333,17 +334,18 @@ __clear_page_buffers(struct page *page)
}
static void free_buffers(struct page *page)
{
- struct buffer_head *bh;
+ struct buffer_head *bh, *head;
if (!PagePrivate(page))
return;
- bh = page_buffers(page);
- while (bh) {
+ bh = head = page_buffers(page);
+ do {
struct buffer_head *next = bh->b_this_page;
free_buffer_head(bh);
bh = next;
- }
+ } while (bh != head);
+
__clear_page_buffers(page);
put_page(page);
}
@@ -362,20 +364,20 @@ static int read_page(struct file *file, unsigned long index,
{
int ret = 0;
struct inode *inode = file_inode(file);
- struct buffer_head *bh;
+ struct buffer_head *bh, *head;
sector_t block;
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, false);
+ bh = head = alloc_page_buffers(page, 1<<inode->i_blkbits, false);
if (!bh) {
ret = -ENOMEM;
goto out;
}
attach_page_buffers(page, bh);
block = index << (PAGE_SHIFT - inode->i_blkbits);
- while (bh) {
+ do {
if (count == 0)
bh->b_blocknr = 0;
else {
@@ -400,7 +402,7 @@ static int read_page(struct file *file, unsigned long index,
}
block++;
bh = bh->b_this_page;
- }
+ } while (bh != head);
page->index = index;
wait_event(bitmap->write_wait,
--
2.6.2
On Tue, Jan 02, 2018 at 02:54:49PM +0800, Sean Fu wrote:
> Modify write_page free_buffers and read_page to support circular buffer
> list.
>
> Signed-off-by: Sean Fu <[email protected]>
> ---
> drivers/md/md-bitmap.c | 36 +++++++++++++++++++-----------------
> 1 file changed, 19 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
> index 239c7bb..b8412c2 100644
> --- a/drivers/md/md-bitmap.c
> +++ b/drivers/md/md-bitmap.c
> @@ -286,7 +286,7 @@ static void bitmap_file_kick(struct bitmap *bitmap);
> */
> static void write_page(struct bitmap *bitmap, struct page *page, int wait)
> {
> - struct buffer_head *bh;
> + struct buffer_head *bh, *head;
>
> if (bitmap->storage.file == NULL) {
> switch (write_sb_page(bitmap, page, wait)) {
> @@ -295,15 +295,16 @@ static void write_page(struct bitmap *bitmap, struct page *page, int wait)
> }
> } else {
>
> - bh = page_buffers(page);
> + bh = head = page_buffers(page);
>
> - while (bh && bh->b_blocknr) {
> - atomic_inc(&bitmap->pending_writes);
> - set_buffer_locked(bh);
> - set_buffer_mapped(bh);
> - submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
> - bh = bh->b_this_page;
> - }
> + do {
> + if (bh && bh->b_blocknr) {
> + atomic_inc(&bitmap->pending_writes);
> + set_buffer_locked(bh);
> + set_buffer_mapped(bh);
> + submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
> + }
> + } while ((bh = bh->b_this_page) != head);
>
> if (wait)
> wait_event(bitmap->write_wait,
> @@ -333,17 +334,18 @@ __clear_page_buffers(struct page *page)
> }
> static void free_buffers(struct page *page)
> {
> - struct buffer_head *bh;
> + struct buffer_head *bh, *head;
>
> if (!PagePrivate(page))
> return;
>
> - bh = page_buffers(page);
> - while (bh) {
> + bh = head = page_buffers(page);
> + do {
> struct buffer_head *next = bh->b_this_page;
> free_buffer_head(bh);
> bh = next;
> - }
> + } while (bh != head);
> +
> __clear_page_buffers(page);
> put_page(page);
> }
> @@ -362,20 +364,20 @@ static int read_page(struct file *file, unsigned long index,
> {
> int ret = 0;
> struct inode *inode = file_inode(file);
> - struct buffer_head *bh;
> + struct buffer_head *bh, *head;
> sector_t block;
>
> 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, false);
> + bh = head = alloc_page_buffers(page, 1<<inode->i_blkbits, false);
> if (!bh) {
> ret = -ENOMEM;
> goto out;
> }
> attach_page_buffers(page, bh);
> block = index << (PAGE_SHIFT - inode->i_blkbits);
> - while (bh) {
> + do {
> if (count == 0)
> bh->b_blocknr = 0;
> else {
> @@ -400,7 +402,7 @@ static int read_page(struct file *file, unsigned long index,
> }
> block++;
> bh = bh->b_this_page;
> - }
> + } while (bh != head);
> page->index = index;
>
> wait_event(bitmap->write_wait,
> --
> 2.6.2
>
Before
sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/buffer.o
text data bss dec hex filename
33693 1466 16 35175 8967 fs/buffer.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size drivers/md/md-bitmap.o
text data bss dec hex filename
28149 2168 0 30317 766d drivers/md/md-bitmap.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/ntfs/mft.o
text data bss dec hex filename
2133 36 0 2169 879 fs/ntfs/mft.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/ntfs/aops.o
text data bss dec hex filename
6125 168 0 6293 1895 fs/ntfs/aops.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size vmlinux
text data bss dec hex filename
11480260 5730762 1646084 18857106 11fbc92 vmlinux
sean@linux-zmni:~/sda5/source/linus_repo/linux> size ./arch/x86/boot/bzImage
size: ./arch/x86/boot/bzImage: Warning: Ignoring section flag IMAGE_SCN_MEM_NOT_PAGED in section .bss
text data bss dec hex filename
6571744 0 16975648 23547392 1674e00 ./arch/x86/boot/bzImage
After
sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/buffer.o
text data bss dec hex filename
33687 1466 16 35169 8961 fs/buffer.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size drivers/md/md-bitmap.o
text data bss dec hex filename
28221 2168 0 30389 76b5 drivers/md/md-bitmap.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/ntfs/mft.o
text data bss dec hex filename
2133 36 0 2169 879 fs/ntfs/mft.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/ntfs/aops.o
text data bss dec hex filename
6125 168 0 6293 1895 fs/ntfs/aops.o
sean@linux-zmni:~/sda5/source/linus_repo/linux> size vmlinux
text data bss dec hex filename
11480270 5730762 1646084 18857116 11fbc9c vmlinux
sean@linux-zmni:~/sda5/source/linus_repo/linux> size ./arch/x86/boot/bzImage
size: ./arch/x86/boot/bzImage: Warning: Ignoring section flag IMAGE_SCN_MEM_NOT_PAGED in section .bss
text data bss dec hex filename
6571488 0 16975904 23547392 1674e00 ./arch/x86/boot/bzImage
Only patch #3 increases the text section size of drivers/md/md-bitmap.o
The actual text section increment should be several bytes. Duo to compiler align-functions option, the total increment is increased to 72 bytes.
Why is circular list traversal more complex than linear list traversal in this situation?
How to optimize it?