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authorLinus Torvalds <torvalds@linux-foundation.org>2009-04-08 17:42:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-08 17:42:32 -0700
commita7b334de4d3651491ccd8c52c744af88d48785b9 (patch)
treedeba5b23183c0c8e9f75b86810b7628ce6d792d5
parent72ae9e092c8a62ef60a364ec812f5f88eb6442fc (diff)
parent430db323fae7665da721768949ade6304811c648 (diff)
Merge branch 'ext3-latency-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
* 'ext3-latency-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: ext3: Try to avoid starting a transaction in writepage for data=writepage block_write_full_page: switch synchronous writes to use WRITE_SYNC_PLUG
-rw-r--r--fs/buffer.c13
-rw-r--r--fs/ext3/inode.c23
2 files changed, 30 insertions, 6 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index 6e35762b6169..13edf7ad3ff1 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1596,6 +1596,16 @@ EXPORT_SYMBOL(unmap_underlying_metadata);
* locked buffer. This only can happen if someone has written the buffer
* directly, with submit_bh(). At the address_space level PageWriteback
* prevents this contention from occurring.
+ *
+ * If block_write_full_page() is called with wbc->sync_mode ==
+ * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this
+ * causes the writes to be flagged as synchronous writes, but the
+ * block device queue will NOT be unplugged, since usually many pages
+ * will be pushed to the out before the higher-level caller actually
+ * waits for the writes to be completed. The various wait functions,
+ * such as wait_on_writeback_range() will ultimately call sync_page()
+ * which will ultimately call blk_run_backing_dev(), which will end up
+ * 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)
@@ -1606,7 +1616,8 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
struct buffer_head *bh, *head;
const unsigned blocksize = 1 << inode->i_blkbits;
int nr_underway = 0;
- int write_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
+ int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
+ WRITE_SYNC_PLUG : WRITE);
BUG_ON(!PageLocked(page));
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 466a332e0bd1..fcfa24361856 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1521,12 +1521,16 @@ static int ext3_ordered_writepage(struct page *page,
if (!page_has_buffers(page)) {
create_empty_buffers(page, inode->i_sb->s_blocksize,
(1 << BH_Dirty)|(1 << BH_Uptodate));
- } else if (!walk_page_buffers(NULL, page_buffers(page), 0, PAGE_CACHE_SIZE, NULL, buffer_unmapped)) {
- /* Provide NULL instead of get_block so that we catch bugs if buffers weren't really mapped */
- return block_write_full_page(page, NULL, wbc);
+ page_bufs = page_buffers(page);
+ } else {
+ page_bufs = page_buffers(page);
+ if (!walk_page_buffers(NULL, page_bufs, 0, PAGE_CACHE_SIZE,
+ NULL, buffer_unmapped)) {
+ /* Provide NULL get_block() to catch bugs if buffers
+ * weren't really mapped */
+ return block_write_full_page(page, NULL, wbc);
+ }
}
- page_bufs = page_buffers(page);
-
handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
if (IS_ERR(handle)) {
@@ -1581,6 +1585,15 @@ static int ext3_writeback_writepage(struct page *page,
if (ext3_journal_current_handle())
goto out_fail;
+ if (page_has_buffers(page)) {
+ if (!walk_page_buffers(NULL, page_buffers(page), 0,
+ PAGE_CACHE_SIZE, NULL, buffer_unmapped)) {
+ /* Provide NULL get_block() to catch bugs if buffers
+ * weren't really mapped */
+ return block_write_full_page(page, NULL, wbc);
+ }
+ }
+
handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);