From: Mingming Cao <cmm@us.ibm.com>
To: Andrew Morton <akpm@osdl.org>, pbadari@us.ibm.com
Cc: suparna@in.ibm.com, sct@redhat.com, linux-kernel@vger.kernel.org,
ext2-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org
Subject: Re: [Ext2-devel] [RFC] Adding multiple block allocation
Date: Fri, 29 Apr 2005 14:12:19 -0700 [thread overview]
Message-ID: <1114809139.10473.70.camel@localhost.localdomain> (raw)
In-Reply-To: <20050429135705.3f4831bd.akpm@osdl.org>
On Fri, 2005-04-29 at 13:57 -0700, Andrew Morton wrote:
> Mingming Cao <cmm@us.ibm.com> wrote:
> >
> > If we do direct write(block allocation) to a hole, I found that the
> > "create" flag passed to ext3_direct_io_get_blocks() is 0 if we are
> > trying to _write_ to a file hole. Is this expected?
>
> Nope. The code in get_more_blocks() is pretty explicit.
>
> > But if it try to allocating blocks in the hole (with direct IO), blocks
> > are allocated one by one. I am looking at it right now.
> >
>
> Please see the comment over get_more_blocks().
>
I went to look at get_more_blocks, the create flag is cleared if the
file offset is less than the i_size. (see code below).
static int get_more_blocks(struct dio *dio)
{
..........
.........
create = dio->rw == WRITE;
if (dio->lock_type == DIO_LOCKING) {
if (dio->block_in_file < (i_size_read(dio->inode) >>
dio->blkbits))
create = 0;
} else if (dio->lock_type == DIO_NO_LOCKING) {
create = 0;
ret = (*dio->get_blocks)(dio->inode, fs_startblk, fs_count,
map_bh, create);
}
When it is trying to direct writing to a hole, the create flag is
cleared so that the underlying filesystem get_blocks() function will
only do a block look up(look up will be failed and no block allocation).
do_direct_IO -> get_more_blocks -> ext3_direct_io_get_blocks. In
get_more_blocks(), do_direct_IO() handles the write to hole situation
by simply return an error of ENOTBLK. In direct_io_worker() it detects
this error then just simply return the size of written byte to 0. The
real write is handled by the buffered I/O. In
__generic_file_aio_write_nolock(), generic_file_buffered_write() will be
called if written by generic_file_direct_write() is 0.
Could you confirm my observation above? Hope I understand this right:
right now direct io write to a hole is actually handled by buffered IO.
If so, there must be some valid reason that I could not see now.
Thanks,
Mingming
next prev parent reply other threads:[~2005-04-29 21:13 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-05 3:51 ext3 allocate-with-reservation latencies Lee Revell
2005-04-05 4:13 ` Ingo Molnar
2005-04-05 6:10 ` Mingming Cao
2005-04-05 16:38 ` Lee Revell
2005-04-06 5:35 ` Mingming Cao
2005-04-06 9:51 ` Stephen C. Tweedie
2005-04-06 16:53 ` Mingming Cao
2005-04-06 18:22 ` Stephen C. Tweedie
2005-04-06 19:03 ` Mingming Cao
2005-04-07 8:14 ` Ingo Molnar
2005-04-07 13:08 ` Stephen C. Tweedie
2005-04-07 19:16 ` Mingming Cao
2005-04-07 23:37 ` Mingming Cao
2005-04-08 14:40 ` Stephen C. Tweedie
2005-04-08 16:06 ` Arjan van de Ven
2005-04-08 18:10 ` Mingming Cao
2005-04-08 18:12 ` Lee Revell
2005-04-11 11:48 ` Stephen C. Tweedie
2005-04-11 18:38 ` Mingming Cao
2005-04-11 19:12 ` Lee Revell
2005-04-11 19:22 ` Lee Revell
2005-04-11 19:57 ` Stephen C. Tweedie
2005-04-12 6:41 ` Mingming Cao
2005-04-12 11:18 ` Stephen C. Tweedie
2005-04-12 23:27 ` Mingming Cao
2005-04-13 10:29 ` Stephen C. Tweedie
[not found] ` <1113597161.3899.80.camel@localhost.localdomain>
2005-04-18 18:00 ` Stephen C. Tweedie
2005-04-18 21:56 ` [Ext2-devel] " Mingming Cao
2005-04-22 22:10 ` [RFC][PATCH] Reduce ext3 allocate-with-reservation lock latencies Mingming Cao
2005-04-28 3:45 ` Lee Revell
2005-04-28 7:37 ` Mingming Cao
2005-04-28 16:12 ` Lee Revell
2005-04-28 18:34 ` Mingming Cao
2005-04-29 6:18 ` Mingming Cao
2005-04-28 19:14 ` [RFC] Adding multiple block allocation to current ext3 Mingming Cao
2005-04-29 13:52 ` [Ext2-devel] [RFC] Adding multiple block allocation Suparna Bhattacharya
2005-04-29 17:10 ` Mingming Cao
2005-04-29 19:42 ` Mingming Cao
2005-04-29 20:57 ` Andrew Morton
2005-04-29 21:12 ` Mingming Cao [this message]
2005-04-29 21:34 ` Andrew Morton
2005-04-30 16:00 ` Suparna Bhattacharya
2005-04-29 18:45 ` Badari Pulavarty
2005-04-29 23:22 ` Mingming Cao
2005-04-30 16:10 ` Suparna Bhattacharya
2005-04-30 17:11 ` Suparna Bhattacharya
2005-04-30 18:07 ` Mingming Cao
2005-05-02 4:46 ` Suparna Bhattacharya
2005-04-30 16:52 ` Suparna Bhattacharya
2005-04-30 0:33 ` Mingming Cao
2005-04-30 0:44 ` Mingming Cao
2005-04-30 17:03 ` Suparna Bhattacharya
2006-01-10 23:26 ` [PATCH 0/5] multiple block allocation to current ext3 Mingming Cao
2006-01-11 5:25 ` Andrew Morton
2006-01-11 19:17 ` Mingming Cao
2006-01-11 19:43 ` Andrew Morton
2006-01-11 21:31 ` Mingming Cao
2006-01-14 1:12 ` Fall back io scheduler for 2.6.15? Mingming Cao
2006-01-14 1:49 ` Andrew Morton
2006-01-14 5:22 ` Dave Jones
2006-01-16 8:43 ` Jens Axboe
2006-01-16 19:45 ` [PATCH] Fall back io scheduler ( Re: [Ext2-devel] Re: Fall back io scheduler for 2.6.15?) Mingming Cao
2006-01-16 19:49 ` Jens Axboe
2006-01-16 19:57 ` Mingming Cao
2006-01-19 19:37 ` Fall back io scheduler for 2.6.15? Nate Diller
2006-01-20 8:10 ` Jens Axboe
2006-01-16 19:38 ` [Ext2-devel] " Mingming Cao
2005-04-29 6:28 ` [PATCH] Reduce ext3 allocate-with-reservation lock latencies Mingming Cao
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