set_page_dirty() runs without the page lock. So
__block_write_full_page() needs to be able to cope with the page's
buffers being dirtied concurrently, on another CPU.
Do this with careful ordering and a test-and-set.
=====================================
--- 2.5.13/mm/page-writeback.c~writepage-versus-set_page_dirty Sun May 5 13:32:01 2002
+++ 2.5.13-akpm/mm/page-writeback.c Sun May 5 13:32:35 2002
@@ -480,6 +480,8 @@ int __set_page_dirty_buffers(struct page
do {
if (buffer_uptodate(bh))
set_buffer_dirty(bh);
+ else
+ buffer_error();
bh = bh->b_this_page;
} while (bh != head);
}
--- 2.5.13/fs/buffer.c~writepage-versus-set_page_dirty Sun May 5 13:32:01 2002
+++ 2.5.13-akpm/fs/buffer.c Sun May 5 13:32:35 2002
@@ -1288,6 +1288,16 @@ static int __block_write_full_page(struc
(1 << BH_Dirty)|(1 << BH_Uptodate));
}
+ /*
+ * Be very careful. We have no exclusion from __set_page_dirty_buffers
+ * here, and the (potentially unmapped) buffers may become dirty at
+ * any time. If a buffer becomes dirty here after we've inspected it
+ * then we just miss that fact, and the page stays dirty.
+ *
+ * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
+ * handle that here by just cleaning them.
+ */
+
block = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
head = page_buffers(page);
bh = head;
@@ -1298,15 +1308,11 @@ static int __block_write_full_page(struc
*/
do {
if (block > last_block) {
- if (buffer_dirty(bh))
- buffer_error();
+ clear_buffer_dirty(bh);
if (buffer_mapped(bh))
buffer_error();
/*
- * NOTE: this buffer can only be marked uptodate
- * because we know that block_write_full_page has
- * zeroed it out. That seems unnecessary and may go
- * away.
+ * The buffer was zeroed by block_write_full_page()
*/
set_buffer_uptodate(bh);
} else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
@@ -1327,11 +1333,9 @@ static int __block_write_full_page(struc
do {
get_bh(bh);
- if (buffer_dirty(bh)) {
+ if (buffer_mapped(bh) && buffer_dirty(bh)) {
lock_buffer(bh);
- if (buffer_dirty(bh)) {
- if (!buffer_mapped(bh))
- buffer_error();
+ if (test_clear_buffer_dirty(bh)) {
if (!buffer_uptodate(bh))
buffer_error();
set_buffer_async_io(bh);
@@ -1353,7 +1357,6 @@ static int __block_write_full_page(struc
do {
struct buffer_head *next = bh->b_this_page;
if (buffer_async(bh)) {
- clear_buffer_dirty(bh);
submit_bh(WRITE, bh);
nr_underway++;
}
-
-
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This archive was generated by hypermail 2b29 : Tue May 07 2002 - 22:00:25 EST