On Fri, Feb 15, 2008 at 11:43:04AM -0800, Mingming Cao wrote:
> On Fri, 2008-02-15 at 23:46 +0530, Aneesh Kumar K.V wrote:
> > fallocate blocks are considered as sparse area and read from them should
> > return zero. ext4_ext_get_blocks should return zero for read request.
> > 
> The patch itself looks harmless, but I still don't see how this could
> fix the problem you described at irc: a write hit a BUG_ON() in
> fs/buffer.c saying the buffer is not mapped. Could you add more details
> here?

Write will take the below call chain

(1)        ext4_ext_get_blocks with create = 0 return allocated
       ll_rw_block  if buffer not uptodate.

ext4_ext_get_blocks at (1) should have returned 0. That would cause
ext4_get_blocks_wrap to again call ext4_ext_get_blocks with create = 1
and that would have returned us the buffer head which is mapped. This
would also result in splitting the extent to initialized and
uninitialized one.

To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Reply via email to