Clean up and make try_to_free_buffers() not race with dirty pages

This is preparatory work in our continuing saga on some hard-to-trigger
file corruption with shared writable mmap() after the dirty page
tracking changes (commit d08b3851da41d0ee60851f2c75b118e1f7a5fc89 etc)
were merged.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/buffer.c b/fs/buffer.c
index d1f1b54d3108c6bb52ebc25ce285451eecab8e9b..263f88e4dffb8bcd617742374d0934d316be948f 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2834,7 +2834,7 @@ int try_to_free_buffers(struct page *page)
        int ret = 0;
 
        BUG_ON(!PageLocked(page));
-       if (PageWriteback(page))
+       if (PageDirty(page) || PageWriteback(page))
                return 0;
 
        if (mapping == NULL) {          /* can this still happen? */
@@ -2845,22 +2845,6 @@ int try_to_free_buffers(struct page *page)
        spin_lock(&mapping->private_lock);
        ret = drop_buffers(page, &buffers_to_free);
        spin_unlock(&mapping->private_lock);
-       if (ret) {
-               /*
-                * If the filesystem writes its buffers by hand (eg ext3)
-                * then we can have clean buffers against a dirty page.  We
-                * clean the page here; otherwise later reattachment of buffers
-                * could encounter a non-uptodate page, which is unresolvable.
-                * This only applies in the rare case where try_to_free_buffers
-                * succeeds but the page is not freed.
-                *
-                * Also, during truncate, discard_buffer will have marked all
-                * the page's buffers clean.  We discover that here and clean
-                * the page also.
-                */
-               if (test_clear_page_dirty(page))
-                       task_io_account_cancelled_write(PAGE_CACHE_SIZE);
-       }
 out:
        if (buffers_to_free) {
                struct buffer_head *bh = buffers_to_free;