On Sun, 17 Sep 2006 22:39:07 +0400
"Vladimir V. Saveliev" <[EMAIL PROTECTED]> wrote:
> Hello
>
> On Friday 15 September 2006 06:24, Andrew Morton wrote:
> > On Wed, 13 Sep 2006 22:12:54 +0400
> > "Vladimir V. Saveliev" <[EMAIL PROTECTED]> wrote:
> >
> > > Hello, Andrew
> > >
> > > reiser4 in 2.6.18-rc6-mm2 has a bug. It can not do readv.
> > >
> > > The attached patch fixes it by implementing reiser4' aio_read file
> > > operation.
> > > Unfortunately, it appeared to get a loop which is very similar to the one
> > > of
> > > fs/read_write.c:do_loop_readv_writev().
> > > Alternatively, if do_loop_readv_writev were EXPORT_SYMBOL-ed
> > > reiser4' aio_read could use it instead. But, there is a problem with
> > > do_loop_readv_writev EXPORT_SYMBOL-ing:
> > > one if its arguments is io_fn_t, which is declared in fs/read_write.h.
> > > If it is ok to move io_fn_t and do_loop_readv_writev declarations to
> > > include/linux/fs.h and to EXPORT_SYMBOL
> > > do_loop_readv_writev the fix will be smaller. Please, let me know what
> > > would you prefer.
> > >
> >
> > Yes, I'd say that do_loop_readv_writev() is suitable for exporting to
> > filesystems, and that doing so is preferable to duplicating it.
> >
> > That'd be two patches, please: one to do the export and one to use it in
> > reiser4.
> >
> > I assume there's a good reason why reiser4 cannot use
> > generic_file_aio_read() or vfs_readv(). Please capture that discussion in
> > the changelog for the first patch, thanks.
> >
>
> It seems the problem can be fixed a bit simpler. Currently, there is a
> difference between read and readv: read calls f_op->read if it is defined,
> but readv calls f_op->read if f_op->aio_read is not defined. The latest is a
> bit unlogical imho:
> wouldn't it be more consistent if readv worked via f_op->read if it is
> defined?
> If we fixed readv (do_readv_writev) that way - reiser4 would not need
> anything from its aio_read but generic_file_aio_read.
>
>
> From: Vladimir Saveliev <[EMAIL PROTECTED]>
>
> There is some asymmetry between read and readv:
> read (vfs_read, namely) calls f_op->read when it is defined,
> while readv (do_readv_writev) calls f_op->read when f_op->aio_read is not
> defined.
> This patch makes do_readv_writev to call do_loop_readv_writev
> (which calls f_op->read for each segment of i/o vector) if f_op->read is
> defined.
>
> Signed-off-by: Vladimir Saveliev <[EMAIL PROTECTED]>
>
>
>
>
> diff -puN fs/read_write.c~fix-do_readv_writev fs/read_write.c
> --- linux-2.6.18-rc6-mm2/fs/read_write.c~fix-do_readv_writev 2006-09-15
> 17:46:03.000000000 +0400
> +++ linux-2.6.18-rc6-mm2-vs/fs/read_write.c 2006-09-17 23:01:17.000000000
> +0400
> @@ -608,7 +608,6 @@ static ssize_t do_readv_writev(int type,
> if (ret)
> goto out;
>
> - fnv = NULL;
> if (type == READ) {
> fn = file->f_op->read;
> fnv = file->f_op->aio_read;
> @@ -617,11 +616,11 @@ static ssize_t do_readv_writev(int type,
> fnv = file->f_op->aio_write;
> }
>
> - if (fnv)
> + if (fn)
> + ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);
> + else
> ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
> pos, fnv);
> - else
> - ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);
>
> out:
> if (iov != iovstack)
>
> _
OK, thanks. I'll wait to hear from Badari and Christoph on that.
