linux-kernel - Re: [PATCHSET] block: clean up bdev claim/release handling

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Date:	Tue, 2 Nov 2010 06:49:18 +1100
From:	Neil Brown <neilb@...e.de>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, hch@...radead.org, linux-kernel@...r.kernel.org,
	petero2@...ia.com, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, jack@...e.cz, akpm@...ux-foundation.org,
	adilger.kernel@...ger.ca, tytso@....edu, mfasheh@...e.com,
	joel.becker@...cle.com, aelder@....com, dm-devel@...hat.com,
	drbd-dev@...ts.linbit.com, leochen@...adcom.com,
	sbranden@...adcom.com, chris.mason@...cle.com, swhiteho@...hat.com,
	shaggy@...ux.vnet.ibm.com, joern@...fs.org,
	konishi.ryusuke@....ntt.co.jp, reiserfs-devel@...r.kernel.org,
	viro@...iv.linux.org.uk
Subject: Re: [PATCHSET] block: clean up bdev claim/release handling

On Mon,  1 Nov 2010 17:15:24 +0100
Tejun Heo <tj@...nel.org> wrote:

> bdev exclusive access handling is somewhat clumsy.  The primary
> interface is bd_claim() and bd_release() but there also are
> open_bdev_exclusive(), close_bdev_exclusive() and bd_claim_by_disk()
> and bd_release_from_disk().
> 
> Gaining exclusive access as a separate step from open itself also has
> the inherent problem that the block layer doesn't know whether the
> current open attempt is for an exclusive access or not.  The action of
> open itself may affect the existing exclusive access but there's no
> way to prevent it.
> 
> This patchset simplifies the claim/release handling by folding it into
> blkdev_get/put() and making others simple wrappers around them.  This
> simplifies code and removes strange corner cases like the
> non-atomicity of exclusive open described above.

He Tejun,
 This looks like a really nice clean-up!  Thanks.
Definitely
  Acked-by: NeilBrown <neilb@...e.de>
for the md parts.

Thanks,
NeilBrown


> 
> There are five patches in this series.
> 
>  0001-mtd-fix-bdev-exclusive-open-bugs-in-block2mtd-add_de.patch
>  0002-btrfs-close_bdev_exclusive-should-use-the-same-flags.patch
>  0003-block-simplify-holder-symlink-handling.patch
>  0004-block-make-blkdev_get-put-handle-exclusive-access.patch
>  0005-block-reorganize-claim-release-implementation.patch
> 
> 0001-0002 are fixes regarding exclusive bdev opens.  0003 simplifies
> holder/slave symlink handling.  0004 folds bdev claim/release into
> blkdev_get/put().  0005 reorganizes implementation a bit.
> 
> Cleaning up claim/release handling enables implementation of in-kernel
> disk event polling which be posted soon.  Although this patchset
> touches various files including drivers and filesystems, the changes
> there are mostly trivial and I think it would be best to route these
> through the block tree.
> 
> This patchset is on top of 2.6.37-rc1 and available in the following
> git tree.
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git
> cleanup-bd_claim
> 
> This patchset reduces about 400 lines of code.
> 
> Thanks.
> 
>  block/ioctl.c                   |    5 
>  drivers/block/drbd/drbd_int.h   |    2 
>  drivers/block/drbd/drbd_main.c  |    7 
>  drivers/block/drbd/drbd_nl.c    |  103 ++-----
>  drivers/block/pktcdvd.c         |   22 -
>  drivers/char/raw.c              |   14 
>  drivers/md/dm-table.c           |   20 -
>  drivers/md/md.c                 |   16 -
>  drivers/mtd/devices/block2mtd.c |   10 
>  drivers/s390/block/dasd_genhd.c |    2 
>  fs/block_dev.c                  |  576
> +++++++++-------------------------------
> fs/btrfs/volumes.c              |   14
> fs/ext3/super.c                 |   12
> fs/ext4/super.c                 |   12
> fs/gfs2/ops_fstype.c            |    4
> fs/jfs/jfs_logmgr.c             |   17 -
> fs/logfs/dev_bdev.c             |    4
> fs/nilfs2/super.c               |    4
> fs/ocfs2/cluster/heartbeat.c    |    2
> fs/partitions/check.c           |    2
> fs/reiserfs/journal.c           |   17 -
> fs/super.c                      |   14
> fs/xfs/linux-2.6/xfs_super.c    |    2
> include/linux/fs.h              |   22 -
> kernel/power/swap.c             |    5
> mm/swapfile.c                   |    7 26 files changed, 260
> insertions(+), 655 deletions(-)
> 
> --
> tejun

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