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Patch "fs/mpage.c: fix mpage_writepage() for pages with buffers" has been added to the 4.13-stable tree

PATCH [email protected] 1 participant 1 message Oct 15, 2017

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This is a note to let you know that I've just added the patch titled

fs/mpage.c: fix mpage_writepage() for pages with buffers

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fs-mpage.c-fix-mpage_writepage-for-pages-with-buffers.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From f892760aa66a2d657deaf59538fb69433036767c Mon Sep 17 00:00:00 2001

From: Matthew Wilcox <[email protected]>
Date: Fri, 13 Oct 2017 15:58:15 -0700
Subject: fs/mpage.c: fix mpage_writepage() for pages with buffers

From: Matthew Wilcox <[email protected]>

commit f892760aa66a2d657deaf59538fb69433036767c upstream.

When using FAT on a block device which supports rw_page, we can hit BUG_ON(!PageLocked(page)) in try_to_free_buffers(). This is because we call clean_buffers() after unlocking the page we've written. Introduce a new clean_page_buffers() which cleans all buffers associated with a page and call it from within bdev_write_page().

---
 fs/block_dev.c              |    6 ++++--
 fs/mpage.c                  |   14 +++++++++++---
 include/linux/buffer_head.h |    1 +
 3 files changed, 16 insertions(+), 5 deletions(-)
fs/block_dev.c +4 -2
@@ -716,10 +716,12 @@ int bdev_write_page(struct block_device
 
 	set_page_writeback(page);
 	result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, true);
-	if (result)
+	if (result) {
 		end_page_writeback(page);
-	else
+	} else {
+		clean_page_buffers(page);
 		unlock_page(page);
+	}
 	blk_queue_exit(bdev->bd_queue);
 	return result;
 }
fs/mpage.c +11 -3
@@ -468,6 +468,16 @@ static void clean_buffers(struct page *p
 		try_to_free_buffers(page);
 }
 
+/*
+ * For situations where we want to clean all buffers attached to a page.
+ * We don't need to calculate how many buffers are attached to the page,
+ * we just need to specify a number larger than the maximum number of buffers.
+ */
+void clean_page_buffers(struct page *page)
+{
+	clean_buffers(page, ~0U);
+}
+
 static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
 		      void *data)
 {
@@ -605,10 +615,8 @@ alloc_new:
 	if (bio == NULL) {
 		if (first_unmapped == blocks_per_page) {
 			if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
-								page, wbc)) {
-				clean_buffers(page, first_unmapped);
+								page, wbc))
 				goto out;
-			}
 		}
 		bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
 				BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH);
include/linux/buffer_head.h +1 -0
@@ -232,6 +232,7 @@ int generic_write_end(struct file *, str
 				loff_t, unsigned, unsigned,
 				struct page *, void *);
 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
+void clean_page_buffers(struct page *page);
 int cont_write_begin(struct file *, struct address_space *, loff_t,
 			unsigned, unsigned, struct page **, void **,
 			get_block_t *, loff_t *);

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/fs-mpage.c-fix-mpage_writepage-for-pages-with-buffers.patch