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Date: Tue, 16 Nov 2010 21:16:08 +0100 (CET)
From: Lukas Czerner <lczerner@...hat.com>
To: Eric Sandeen <sandeen@...hat.com>
cc: Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org,
tytso@....edu, adilger@...ger.ca
Subject: Re: [PATCH 1/7] e2fsprogs: Add discard function into
struct_io_manager
On Tue, 16 Nov 2010, Eric Sandeen wrote:
> On 10/26/10 12:54 PM, Lukas Czerner wrote:
> > In order to provide generic "discard" function for all e2fsprogs tools
> > add a discard function prototype into struct_io_manager. Specific
> > function for specific io managers can be crated that way.
> >
> > This commit also creates unix_discard function which uses BLKDISCARD
> > ioctl to discard data blocks on the block device and bind it into
> > unit_io_manager structure to be available for all e2fsprogs tools.
> > Note that BLKDISCARD is still Linux specific ioctl, however other
> > unix systems may provide similar functionality. So far the
> > unix_discard() remains linux specific hence is embedded in #ifdef
> > __linux__ macro.
> >
> > Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> > ---
> > lib/ext2fs/ext2_io.h | 2 ++
> > lib/ext2fs/unix_io.c | 41 +++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 43 insertions(+), 0 deletions(-)
> >
> > diff --git a/lib/ext2fs/ext2_io.h b/lib/ext2fs/ext2_io.h
> > index ccc9c8b..d202007 100644
> > --- a/lib/ext2fs/ext2_io.h
> > +++ b/lib/ext2fs/ext2_io.h
> > @@ -83,6 +83,8 @@ struct struct_io_manager {
> > int count, void *data);
> > errcode_t (*write_blk64)(io_channel channel, unsigned long long block,
> > int count, const void *data);
> > + errcode_t (*discard)(io_channel channel, unsigned long long block,
> > + unsigned long long count, const void *data);
> > long reserved[16];
> > };
> >
> > diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
> > index 1df1fdd..5b6cdec 100644
> > --- a/lib/ext2fs/unix_io.c
> > +++ b/lib/ext2fs/unix_io.c
> > @@ -115,6 +115,8 @@ static errcode_t unix_read_blk64(io_channel channel, unsigned long long block,
> > int count, void *data);
> > static errcode_t unix_write_blk64(io_channel channel, unsigned long long block,
> > int count, const void *data);
> > +static errcode_t unix_discard(io_channel channel, unsigned long long block,
> > + unsigned long long count, const void *data);
> >
> > static struct struct_io_manager struct_unix_manager = {
> > EXT2_ET_MAGIC_IO_MANAGER,
> > @@ -130,6 +132,7 @@ static struct struct_io_manager struct_unix_manager = {
> > unix_get_stats,
> > unix_read_blk64,
> > unix_write_blk64,
> > + unix_discard,
> > };
> >
> > io_manager unix_io_manager = &struct_unix_manager;
> > @@ -834,3 +837,41 @@ static errcode_t unix_set_option(io_channel channel, const char *option,
> > }
> > return EXT2_ET_INVALID_ARGUMENT;
> > }
> > +
> > +#ifdef __linux__
> > +
> > +#ifndef BLKDISCARD
> > +#define BLKDISCARD _IO(0x12,119)
> > +#endif
> > +
> > +static errcode_t unix_discard(io_channel channel, unsigned long long block,
> > + unsigned long long count, const void *data)
> > +{
> > +
> > + struct struct_ext2_filsys *fs;
> > + struct unix_private_data *u_priv;
> > + errcode_t retval = 0;
> > + __uint64_t range[2];
> > + int blocksize;
> > +
> > + EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
> > + u_priv = (struct unix_private_data *) channel->private_data;
> > + EXT2_CHECK_MAGIC(u_priv, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
> > +
> > + fs = (struct struct_ext2_filsys *) data;
> > + if (!fs)
> > + return EXT2_ET_INVALID_ARGUMENT;
> > +
> > + blocksize = EXT2_BLOCK_SIZE(fs->super);
>
> This seems a little convoluted; you pass in *data, which gets you the fs,
> from which you get the super, from which you get the blocksize,
> which is all that you ever actually use here:
>
> > + range[0] = (__uint64_t)(block);
> > + range[1] = (__uint64_t)(count);
> > + range[0] *= (__uint64_t)(blocksize);
> > + range[1] *= (__uint64_t)(blocksize);
>
> any reason to not just pass in the blocksize?
>
> Maybe this is for flexibility for not-linux, but I guess we don't know what
> they need anyway...?
>
> And if you do that you can change "u_priv" to "data" just to match the
> other handlers, perhaps.
You're right, I was so closely following the example that I forget that
it can be done more simply. Does this looks good to you ?
static errcode_t unix_discard(io_channel channel, unsigned long long block,
unsigned long long count, const void *blocksize)
{
unsigned int *bsize = (unsigned int *) blocksize;
struct unix_private_data *data;
errcode_t retval = 0;
__uint64_t range[2];
EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
data = (struct unix_private_data *) channel->private_data;
EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
if (!blocksize)
return EXT2_ET_INVALID_ARGUMENT;
range[0] = (__uint64_t)(block);
range[1] = (__uint64_t)(count);
range[0] *= (__uint64_t)(*bsize);
range[1] *= (__uint64_t)(*bsize);
return ioctl(data->dev, BLKDISCARD, &range);
}
then we can call it like this:
ret = manager->discard(fs->io, start, count, &fs->blocksize);
Thanks a lot for reviewing this!
-Lukas
>
> -Eric
>
> > + return ioctl(u_priv->dev, BLKDISCARD, &range);
> > +}
> > +
> > +#else
> > +#define unix_discard(channel, block, count) EXT2_ET_UNIMPLEMENTED
> > +#endif
>
>
--
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