ext4: BUG_ON fix: check if page has buffers before calling page_buffers() (b1142e8f) · Commits · 戴 / test

We need to make check if a page does not have buffes by checking page_has_buffers(page) before calling page_buffers(page) in ext4_writepage(). Otherwise page_buffers() could throw a BUG_ON. Thanks also to Markus Trippelsdorf and Avinash Kurup who also reported the problem. Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu> Reported-by:

Sedat Dilek <sedat.dilek@googlemail.com> Tested-by:

Sedat Dilek <sedat.dilek@googlemail.com>

fs/ext4/inode.c

+5 −7

Original line number	Diff line number	Diff line
		@@ -2718,7 +2718,7 @@ static int ext4_writepage(struct page *page,
		* try to create them using __block_write_begin. If this
		* fails, redirty the page and move on.
		*/
		if (!page_buffers(page)) {
		if (!page_has_buffers(page)) {
		if (__block_write_begin(page, 0, len,
		noalloc_get_block_write)) {
		redirty_page:
		@@ -2732,12 +2732,10 @@ static int ext4_writepage(struct page *page,
		if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
		ext4_bh_delay_or_unwritten)) {
		/*
		* We don't want to do block allocation So redirty the
		* page and return We may reach here when we do a
		* journal commit via
		* journal_submit_inode_data_buffers. If we don't
		* have mapping block we just ignore them. We can also
		* reach here via shrink_page_list
		* We don't want to do block allocation, so redirty
		* the page and return. We may reach here when we do
		* a journal commit via journal_submit_inode_data_buffers.
		* We can also reach here via shrink_page_list
		*/
		goto redirty_page;
		}

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