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 ext4_write_begin block_write_begin __block_prepare_write ext4_getblock ext4_get_blocks_wrap (1) ext4_ext_get_blocks with create = 0 return allocated ll_rw_block if buffer not uptodate. submit_bh BUG_ON(!buffer_mapped(bh)) 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. -aneesh - 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