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Commit a827eaff authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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ext4: Take page lock before looking at attached buffer_heads flags 



In order to check whether the buffer_heads are mapped we need to hold
page lock. Otherwise a reclaim can cleanup the attached buffer_heads.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 44fc48f7

fs/ext4/inode.c

+11 −2
Original line number Diff line number Diff line
@@ -5286,12 +5286,21 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) 
	else

		len = PAGE_CACHE_SIZE;



	lock_page(page);

	/*

	 * return if we have all the buffers mapped. This avoid

	 * the need to call write_begin/write_end which does a

	 * journal_start/journal_stop which can block and take

	 * long time

	 */

	if (page_has_buffers(page)) {

		/* return if we have all the buffers mapped */

		if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,

				       ext4_bh_unmapped))

					ext4_bh_unmapped)) {

			unlock_page(page);

			goto out_unlock;

		}

	}

	unlock_page(page);

	/*

	 * OK, we need to fill the hole... Do write_begin write_end

	 * to do block allocation/reservation.We are not holding