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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: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Aneesh Kumar K.V 2009-09-09 22:36:03 -04:00 committed by Theodore Ts'o
parent 44fc48f704
commit a827eaffff
1 changed files with 11 additions and 2 deletions
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13
fs/ext4/inode.c
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@ -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