[PATCH] set_page_dirty() return value fixes

We need set_page_dirty() to return true if it actually transitioned the page
from a clean to dirty state.  This wasn't right in a couple of places.  Do a
kernel-wide audit, fix things up.

This leaves open the possibility of returning a negative errno from
set_page_dirty() sometime in the future.  But we don't do that at present.

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

5 files changed, 11 insertions, 9 deletions

diff --git a/arch/cris/arch-v32/drivers/cryptocop.c b/arch/cris/arch-v32/drivers/cryptocop.c
index 501fa52..c59ee28 100644
--- a/arch/cris/arch-v32/drivers/cryptocop.c
+++ b/arch/cris/arch-v32/drivers/cryptocop.c
@@ -2944,7 +2944,7 @@ static int cryptocop_ioctl_process(struct inode *inode, struct file *filp, unsig
 		int spdl_err;
 		/* Mark output pages dirty. */
 		spdl_err = set_page_dirty_lock(outpages[i]);
-		DEBUG(if (spdl_err)printk("cryptocop_ioctl_process: set_page_dirty_lock returned %d\n", spdl_err));
+		DEBUG(if (spdl_err < 0)printk("cryptocop_ioctl_process: set_page_dirty_lock returned %d\n", spdl_err));
 	}
 	for (i = 0; i < nooutpages; i++){
 		put_page(outpages[i]);
diff --git a/drivers/block/rd.c b/drivers/block/rd.c
index 1c54f46..940bfd7 100644
--- a/drivers/block/rd.c
+++ b/drivers/block/rd.c
@@ -186,7 +186,8 @@ static int ramdisk_writepages(struct address_space *mapping,
  */
 static int ramdisk_set_page_dirty(struct page *page)
 {
-	SetPageDirty(page);
+	if (!TestSetPageDirty(page))
+		return 1;
 	return 0;
 }
 
diff --git a/fs/buffer.c b/fs/buffer.c
index 11ca6eb..24262ea 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -865,8 +865,8 @@ int __set_page_dirty_buffers(struct page *page)
 		}
 		write_unlock_irq(&mapping->tree_lock);
 		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+		return 1;
 	}
-	
 	return 0;
 }
 EXPORT_SYMBOL(__set_page_dirty_buffers);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0ad70c1..092cfae 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -350,7 +350,7 @@ struct address_space_operations {
 	/* Write back some dirty pages from this mapping. */
 	int (*writepages)(struct address_space *, struct writeback_control *);
 
-	/* Set a page dirty */
+	/* Set a page dirty.  Return true if this dirtied it */
 	int (*set_page_dirty)(struct page *page);
 
 	int (*readpages)(struct file *filp, struct address_space *mapping,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c67ddc4..893d767 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -628,8 +628,6 @@ EXPORT_SYMBOL(write_one_page);
  */
 int __set_page_dirty_nobuffers(struct page *page)
 {
-	int ret = 0;
-
 	if (!TestSetPageDirty(page)) {
 		struct address_space *mapping = page_mapping(page);
 		struct address_space *mapping2;
@@ -651,8 +649,9 @@ int __set_page_dirty_nobuffers(struct page *page)
 							I_DIRTY_PAGES);
 			}
 		}
+		return 1;
 	}
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL(__set_page_dirty_nobuffers);
 
@@ -682,8 +681,10 @@ int fastcall set_page_dirty(struct page *page)
 			return (*spd)(page);
 		return __set_page_dirty_buffers(page);
 	}
-	if (!PageDirty(page))
-		SetPageDirty(page);
+	if (!PageDirty(page)) {
+		if (!TestSetPageDirty(page))
+			return 1;
+	}
 	return 0;
 }
 EXPORT_SYMBOL(set_page_dirty);