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Subject[PATCH 2/3] Add block_write_full_page_endio for passing endio handler
Date
block_write_full_page doesn't allow the caller to control what happens
when the IO is over. This adds a new call named block_write_full_page_endio
so the buffer head end_io handler can be provided by the caller.

This will be used by the ext3 data=guarded mode to do i_size updates
in a workqueue based end_io handler. end_buffer_async_write is also
exported so it can be called to do the dirty work of managing
page writeback for the higher level end_io handler.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---
fs/buffer.c | 45 ++++++++++++++++++++++++++++++++----------
include/linux/buffer_head.h | 3 ++
2 files changed, 37 insertions(+), 11 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 13edf7a..308865b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -360,7 +360,7 @@ still_busy:
* Completion handler for block_write_full_page() - pages which are unlocked
* during I/O, and which have PageWriteback cleared upon I/O completion.
*/
-static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
+void end_buffer_async_write(struct buffer_head *bh, int uptodate)
{
char b[BDEVNAME_SIZE];
unsigned long flags;
@@ -438,11 +438,17 @@ static void mark_buffer_async_read(struct buffer_head *bh)
set_buffer_async_read(bh);
}

-void mark_buffer_async_write(struct buffer_head *bh)
+void mark_buffer_async_write_endio(struct buffer_head *bh,
+ bh_end_io_t *handler)
{
- bh->b_end_io = end_buffer_async_write;
+ bh->b_end_io = handler;
set_buffer_async_write(bh);
}
+
+void mark_buffer_async_write(struct buffer_head *bh)
+{
+ mark_buffer_async_write_endio(bh, end_buffer_async_write);
+}
EXPORT_SYMBOL(mark_buffer_async_write);


@@ -1608,7 +1614,8 @@ EXPORT_SYMBOL(unmap_underlying_metadata);
* unplugging the device queue.
*/
static int __block_write_full_page(struct inode *inode, struct page *page,
- get_block_t *get_block, struct writeback_control *wbc)
+ get_block_t *get_block, struct writeback_control *wbc,
+ bh_end_io_t *handler)
{
int err;
sector_t block;
@@ -1693,7 +1700,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
continue;
}
if (test_clear_buffer_dirty(bh)) {
- mark_buffer_async_write(bh);
+ mark_buffer_async_write_endio(bh, handler);
} else {
unlock_buffer(bh);
}
@@ -1746,7 +1753,7 @@ recover:
if (buffer_mapped(bh) && buffer_dirty(bh) &&
!buffer_delay(bh)) {
lock_buffer(bh);
- mark_buffer_async_write(bh);
+ mark_buffer_async_write_endio(bh, handler);
} else {
/*
* The buffer may have been set dirty during
@@ -2672,7 +2679,8 @@ int nobh_writepage(struct page *page, get_block_t *get_block,
out:
ret = mpage_writepage(page, get_block, wbc);
if (ret == -EAGAIN)
- ret = __block_write_full_page(inode, page, get_block, wbc);
+ ret = __block_write_full_page(inode, page, get_block, wbc,
+ end_buffer_async_write);
return ret;
}
EXPORT_SYMBOL(nobh_writepage);
@@ -2830,9 +2838,10 @@ out:

/*
* The generic ->writepage function for buffer-backed address_spaces
+ * this form passes in the end_io handler used to finish the IO.
*/
-int block_write_full_page(struct page *page, get_block_t *get_block,
- struct writeback_control *wbc)
+int block_write_full_page_endio(struct page *page, get_block_t *get_block,
+ struct writeback_control *wbc, bh_end_io_t *handler)
{
struct inode * const inode = page->mapping->host;
loff_t i_size = i_size_read(inode);
@@ -2841,7 +2850,8 @@ int block_write_full_page(struct page *page, get_block_t *get_block,

/* Is the page fully inside i_size? */
if (page->index < end_index)
- return __block_write_full_page(inode, page, get_block, wbc);
+ return __block_write_full_page(inode, page, get_block, wbc,
+ handler);

/* Is the page fully outside i_size? (truncate in progress) */
offset = i_size & (PAGE_CACHE_SIZE-1);
@@ -2864,9 +2874,20 @@ int block_write_full_page(struct page *page, get_block_t *get_block,
* writes to that region are not written out to the file."
*/
zero_user_segment(page, offset, PAGE_CACHE_SIZE);
- return __block_write_full_page(inode, page, get_block, wbc);
+ return __block_write_full_page(inode, page, get_block, wbc, handler);
}

+/*
+ * The generic ->writepage function for buffer-backed address_spaces
+ */
+int block_write_full_page(struct page *page, get_block_t *get_block,
+ struct writeback_control *wbc)
+{
+ return block_write_full_page_endio(page, get_block, wbc,
+ end_buffer_async_write);
+}
+
+
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
get_block_t *get_block)
{
@@ -3335,9 +3356,11 @@ EXPORT_SYMBOL(block_read_full_page);
EXPORT_SYMBOL(block_sync_page);
EXPORT_SYMBOL(block_truncate_page);
EXPORT_SYMBOL(block_write_full_page);
+EXPORT_SYMBOL(block_write_full_page_endio);
EXPORT_SYMBOL(cont_write_begin);
EXPORT_SYMBOL(end_buffer_read_sync);
EXPORT_SYMBOL(end_buffer_write_sync);
+EXPORT_SYMBOL(end_buffer_async_write);
EXPORT_SYMBOL(file_fsync);
EXPORT_SYMBOL(generic_block_bmap);
EXPORT_SYMBOL(generic_cont_expand_simple);
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 7b73bb8..16ed028 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -155,6 +155,7 @@ void create_empty_buffers(struct page *, unsigned long,
unsigned long b_state);
void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
+void end_buffer_async_write(struct buffer_head *bh, int uptodate);

/* Things to do with buffers at mapping->private_list */
void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
@@ -197,6 +198,8 @@ extern int buffer_heads_over_limit;
void block_invalidatepage(struct page *page, unsigned long offset);
int block_write_full_page(struct page *page, get_block_t *get_block,
struct writeback_control *wbc);
+int block_write_full_page_endio(struct page *page, get_block_t *get_block,
+ struct writeback_control *wbc, bh_end_io_t *handler);
int block_read_full_page(struct page*, get_block_t*);
int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
unsigned long from);
--
1.6.0.2


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