From: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/buffer.c | 29 ++++++++++++++++-------------
1 files changed, 16 insertions(+), 13 deletions(-)
diff -puN fs/buffer.c~block_write_full_page-comment-fixes fs/buffer.c
--- 25/fs/buffer.c~block_write_full_page-comment-fixes 2004-07-08 21:38:53.103529400 -0700
+++ 25-akpm/fs/buffer.c 2004-07-08 21:42:26.275122392 -0700
@@ -1589,10 +1589,9 @@ __bread(struct block_device *bdev, secto
EXPORT_SYMBOL(__bread);
/*
- * invalidate_bh_lrus() is called rarely - at unmount. Because it is only for
- * unmount it only needs to ensure that all buffers from the target device are
- * invalidated on return and it doesn't need to worry about new buffers from
- * that device being added - the unmount code has to prevent that.
+ * invalidate_bh_lrus() is called rarely - but not only at unmount.
+ * This doesn't race because it runs in each cpu either in irq
+ * or with preempt disabled.
*/
static void invalidate_bh_lru(void *arg)
{
@@ -1810,10 +1809,10 @@ EXPORT_SYMBOL(unmap_underlying_metadata)
* state inside lock_buffer().
*
* If block_write_full_page() is called for regular writeback
- * (called_for_sync() is false) then it will redirty a page which has a 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.
+ * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
+ * 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.
*/
static int __block_write_full_page(struct inode *inode, struct page *page,
get_block_t *get_block, struct writeback_control *wbc)
@@ -1902,14 +1901,14 @@ static int __block_write_full_page(struc
}
} while ((bh = bh->b_this_page) != head);
+ /*
+ * The page and its buffers are protected by PageWriteback(), so we can
+ * drop the bh refcounts early.
+ */
BUG_ON(PageWriteback(page));
- set_page_writeback(page); /* Keeps try_to_free_buffers() away */
+ set_page_writeback(page);
unlock_page(page);
- /*
- * The page may come unlocked any time after the *first* submit_bh()
- * call. Be careful with its buffers.
- */
do {
struct buffer_head *next = bh->b_this_page;
if (buffer_async_write(bh)) {
@@ -1939,6 +1938,10 @@ done:
if (uptodate)
SetPageUptodate(page);
end_page_writeback(page);
+ /*
+ * The page and buffer_heads can be released at any time from
+ * here on.
+ */
wbc->pages_skipped++; /* We didn't write this page */
}
return err;
_