Re: [PATCH] ext4: Need clear buffer_delay after page writeout for delayed allocation

quoted

Buffer marked as delay is also mapped
fs/ext4/inode.c

1437                 map_bh(bh_result, inode->i_sb, 0);
1438                 set_buffer_new(bh_result);
1439                 set_buffer_delay(bh_result);

I find a better place to handle this, it make sense to clear this bit in
block_write_full_page() after get_block() returns successfully. This
handles partial error case smoothly. Updated patch below (to replace the
original patch)

ext4: Need clear buffer_delay in block_write_full_page() after allocation

From: Mingming Cao <redacted>

Normally delayed buffer could be cleared in mpage_da_map_blocks(), after
blocks are successfully allocated. But if allocation failed, it will
keep buffer_delay marked and deferring to later 
ext4_da_writepage()(via block_write_full_page()) to do block allocation.
This patch handles clear bh delay bit in this case. Clear buffer_delay
in block_write_full_page() after the block is allocated.

This patch also fixed a bug in block_write_full_page() error case, we need
to check the delayed flag before flush bh to disk when trying to recover from
error.

Signed-off-by: Mingming Cao <redacted>

---
 fs/buffer.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6.26-rc4/fs/buffer.c
===================================================================

--- linux-2.6.26-rc4.orig/fs/buffer.c	2008-06-02 21:34:30.000000000 -0700
+++ linux-2.6.26-rc4/fs/buffer.c	2008-06-02 21:35:17.000000000 -0700

@@ -1697,6 +1697,7 @@ static int __block_write_full_page(struc
 			err = get_block(inode, block, bh, 1);
 			if (err)
 				goto recover;
+			clear_buffer_delay(bh);

 			if (buffer_new(bh)) {
 				/* blockdev mappings never come here */
 				clear_buffer_new(bh);

@@ -1775,7 +1776,8 @@ recover:
 	bh = head;
 	/* Recovery: lock and submit the mapped buffers */
 	do {
-		if (buffer_mapped(bh) && buffer_dirty(bh)) {
+		if (buffer_mapped(bh) && buffer_dirty(bh)
+			&& !buffer_delay(bh)) {
 			lock_buffer(bh);
 			mark_buffer_async_write(bh);
 		} else {