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>
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@ -5286,12 +5286,21 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
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else
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else
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len = PAGE_CACHE_SIZE;
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len = PAGE_CACHE_SIZE;
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lock_page(page);
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/*
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* return if we have all the buffers mapped. This avoid
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* the need to call write_begin/write_end which does a
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* journal_start/journal_stop which can block and take
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* long time
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*/
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if (page_has_buffers(page)) {
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if (page_has_buffers(page)) {
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/* return if we have all the buffers mapped */
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if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
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if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
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ext4_bh_unmapped))
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ext4_bh_unmapped)) {
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unlock_page(page);
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goto out_unlock;
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goto out_unlock;
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}
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}
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}
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unlock_page(page);
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/*
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/*
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* OK, we need to fill the hole... Do write_begin write_end
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* OK, we need to fill the hole... Do write_begin write_end
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* to do block allocation/reservation.We are not holding
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* to do block allocation/reservation.We are not holding
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