Attachment 306906 Details for Bug 447920 – Upstream attempt at a readpage lock ordering fix

[patch] Upstream attempt at a readpage lock ordering fix

readpage-fix.diff (text/plain), 1.75 KB, created by Steve Whitehouse on 2008-05-28 09:12:00 UTC

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Creator: Steve Whitehouse

Created: 2008-05-28 09:12:00 UTC

Size: 1.75 KB

patch

obsolete

>diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
>index 2b556dd..c65257e 100644
>--- a/fs/gfs2/ops_address.c
>+++ b/fs/gfs2/ops_address.c
>@@ -499,31 +499,41 @@ static int __gfs2_readpage(void *file, struct page *page)
>  * @file: The file to read
>  * @page: The page of the file
>  *
>- * This deals with the locking required. We use a trylock in order to
>- * avoid the page lock / glock ordering problems returning AOP_TRUNCATED_PAGE
>- * in the event that we are unable to get the lock.
>+ * This deals with the locking required. We ignore the passed page
>+ * and look it up ourselves. We return success only if the page we
>+ * found matches the one we were passed and we read it successfully.
>  */
> 
> static int gfs2_readpage(struct file *file, struct page *page)
> {
>-	struct gfs2_inode *ip = GFS2_I(page->mapping->host);
>+	struct address_space *mapping = page->mapping;
>+	struct gfs2_inode *ip = GFS2_I(mapping->host);
> 	struct gfs2_holder gh;
>+	unsigned long index = page->index;
>+	struct page *page2 = NULL;
> 	int error;
> 
>-	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|LM_FLAG_TRY_1CB, &gh);
>+	unlock_page(page);
>+	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME, &gh);
> 	error = gfs2_glock_nq_atime(&gh);
>-	if (unlikely(error)) {
>-		unlock_page(page);
>+	if (unlikely(error))
> 		goto out;
>-	}
>-	error = __gfs2_readpage(file, page);
>+	error = AOP_TRUNCATED_PAGE;
>+	page2 = find_lock_page(mapping, index);
>+	if (!page2)
>+		goto unlock;
>+	error = 0;
>+	if (PageUptodate(page2))
>+		unlock_page(page2);
>+	else
>+		error = __gfs2_readpage(file, page2);
>+	page_cache_release(page2);
>+unlock:
> 	gfs2_glock_dq(&gh);
> out:
> 	gfs2_holder_uninit(&gh);
>-	if (error == GLR_TRYFAILED) {
>-		yield();
>+	if (error == 0 && page != page2)
> 		return AOP_TRUNCATED_PAGE;
>-	}
> 	return error;
> }
>

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Attachments on bug 447920: 306378 | 306379 | 306427 | 306428 | 306497 | 306817 | 306906 | 307044