On Tue, Aug 25, 2009 at 07:52:59PM +0530, Aneesh Kumar K.V wrote: > Inorder to check whether the buffer_heads are mapped we need > to hold page lock. Otherwise a reclaim can cleanup the attached > buffer_heads. Instead of taking page lock and check whether > buffer_heads are mapped we let the write_begin/write_end callback > does the equivalent. It does have a performance impact in that we > are doing more work if we the buffer_heads are already mapped. I'm not sure I understand the commit description. From the patch you are removing the check to see if all of the buffers are mapped. But the patch isn't moving the check to ext4_write_begin() or ext4_write_end(). Are you saying the check is already in ext4_write_begin()? It doesn't seem to be in ext4_write_end(). I see that we do call write_page_buffers() in ext4_write_begin(), and in do_journal_get_write_access() we do check to see if the buffers are present. But if they aren't, we don't return an error; we just fail request journal write access for the buffer head. Am I missing something? This patch doesn't feel complete, or the commit description is very confusing.... - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
