From e525fd89d380c4a94c0d63913a1dd1a593ed25e7 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sat, 13 Nov 2010 11:55:17 +0100 Subject: block: make blkdev_get/put() handle exclusive access Over time, block layer has accumulated a set of APIs dealing with bdev open, close, claim and release. * blkdev_get/put() are the primary open and close functions. * bd_claim/release() deal with exclusive open. * open/close_bdev_exclusive() are combination of open and claim and the other way around, respectively. * bd_link/unlink_disk_holder() to create and remove holder/slave symlinks. * open_by_devnum() wraps bdget() + blkdev_get(). The interface is a bit confusing and the decoupling of open and claim makes it impossible to properly guarantee exclusive access as in-kernel open + claim sequence can disturb the existing exclusive open even before the block layer knows the current open if for another exclusive access. Reorganize the interface such that, * blkdev_get() is extended to include exclusive access management. @holder argument is added and, if is @FMODE_EXCL specified, it will gain exclusive access atomically w.r.t. other exclusive accesses. * blkdev_put() is similarly extended. It now takes @mode argument and if @FMODE_EXCL is set, it releases an exclusive access. Also, when the last exclusive claim is released, the holder/slave symlinks are removed automatically. * bd_claim/release() and close_bdev_exclusive() are no longer necessary and either made static or removed. * bd_link_disk_holder() remains the same but bd_unlink_disk_holder() is no longer necessary and removed. * open_bdev_exclusive() becomes a simple wrapper around lookup_bdev() and blkdev_get(). It also has an unexpected extra bdev_read_only() test which probably should be moved into blkdev_get(). * open_by_devnum() is modified to take @holder argument and pass it to blkdev_get(). Most of bdev open/close operations are unified into blkdev_get/put() and most exclusive accesses are tested atomically at the open time (as it should). This cleans up code and removes some, both valid and invalid, but unnecessary all the same, corner cases. open_bdev_exclusive() and open_by_devnum() can use further cleanup - rename to blkdev_get_by_path() and blkdev_get_by_devt() and drop special features. Well, let's leave them for another day. Most conversions are straight-forward. drbd conversion is a bit more involved as there was some reordering, but the logic should stay the same. Signed-off-by: Tejun Heo Acked-by: Neil Brown Acked-by: Ryusuke Konishi Acked-by: Mike Snitzer Acked-by: Philipp Reisner Cc: Peter Osterlund Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Jan Kara Cc: Andrew Morton Cc: Andreas Dilger Cc: "Theodore Ts'o" Cc: Mark Fasheh Cc: Joel Becker Cc: Alex Elder Cc: Christoph Hellwig Cc: dm-devel@redhat.com Cc: drbd-dev@lists.linbit.com Cc: Leo Chen Cc: Scott Branden Cc: Chris Mason Cc: Steven Whitehouse Cc: Dave Kleikamp Cc: Joern Engel Cc: reiserfs-devel@vger.kernel.org Cc: Alexander Viro --- fs/super.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'fs/super.c') diff --git a/fs/super.c b/fs/super.c index ca696155cd9a..22374bf0ba87 100644 --- a/fs/super.c +++ b/fs/super.c @@ -801,13 +801,13 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, /* * s_umount nests inside bd_mutex during - * __invalidate_device(). close_bdev_exclusive() - * acquires bd_mutex and can't be called under - * s_umount. Drop s_umount temporarily. This is safe - * as we're holding an active reference. + * __invalidate_device(). blkdev_put() acquires + * bd_mutex and can't be called under s_umount. Drop + * s_umount temporarily. This is safe as we're + * holding an active reference. */ up_write(&s->s_umount); - close_bdev_exclusive(bdev, mode); + blkdev_put(bdev, mode | FMODE_EXCL); down_write(&s->s_umount); } else { char b[BDEVNAME_SIZE]; @@ -831,7 +831,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, error_s: error = PTR_ERR(s); error_bdev: - close_bdev_exclusive(bdev, mode); + blkdev_put(bdev, mode | FMODE_EXCL); error: return ERR_PTR(error); } @@ -862,7 +862,7 @@ void kill_block_super(struct super_block *sb) bdev->bd_super = NULL; generic_shutdown_super(sb); sync_blockdev(bdev); - close_bdev_exclusive(bdev, mode); + blkdev_put(bdev, mode | FMODE_EXCL); } EXPORT_SYMBOL(kill_block_super); -- cgit v1.2.2 From d4d77629953eabd3c14f6fa5746f6b28babfc55f Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sat, 13 Nov 2010 11:55:18 +0100 Subject: block: clean up blkdev_get() wrappers and their users After recent blkdev_get() modifications, open_by_devnum() and open_bdev_exclusive() are simple wrappers around blkdev_get(). Replace them with blkdev_get_by_dev() and blkdev_get_by_path(). blkdev_get_by_dev() is identical to open_by_devnum(). blkdev_get_by_path() is slightly different in that it doesn't automatically add %FMODE_EXCL to @mode. All users are converted. Most conversions are mechanical and don't introduce any behavior difference. There are several exceptions. * btrfs now sets FMODE_EXCL in btrfs_device->mode, so there's no reason to OR it explicitly on blkdev_put(). * gfs2, nilfs2 and the generic mount_bdev() now set FMODE_EXCL in sb->s_mode. * With the above changes, sb->s_mode now always should contain FMODE_EXCL. WARN_ON_ONCE() added to kill_block_super() to detect errors. The new blkdev_get_*() functions are with proper docbook comments. While at it, add function description to blkdev_get() too. Signed-off-by: Tejun Heo Cc: Philipp Reisner Cc: Neil Brown Cc: Mike Snitzer Cc: Joern Engel Cc: Chris Mason Cc: Jan Kara Cc: "Theodore Ts'o" Cc: KONISHI Ryusuke Cc: reiserfs-devel@vger.kernel.org Cc: xfs-masters@oss.sgi.com Cc: Alexander Viro --- fs/super.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'fs/super.c') diff --git a/fs/super.c b/fs/super.c index 22374bf0ba87..5d9a4497849a 100644 --- a/fs/super.c +++ b/fs/super.c @@ -766,13 +766,13 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, { struct block_device *bdev; struct super_block *s; - fmode_t mode = FMODE_READ; + fmode_t mode = FMODE_READ | FMODE_EXCL; int error = 0; if (!(flags & MS_RDONLY)) mode |= FMODE_WRITE; - bdev = open_bdev_exclusive(dev_name, mode, fs_type); + bdev = blkdev_get_by_path(dev_name, mode, fs_type); if (IS_ERR(bdev)) return ERR_CAST(bdev); @@ -807,7 +807,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, * holding an active reference. */ up_write(&s->s_umount); - blkdev_put(bdev, mode | FMODE_EXCL); + blkdev_put(bdev, mode); down_write(&s->s_umount); } else { char b[BDEVNAME_SIZE]; @@ -831,7 +831,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, error_s: error = PTR_ERR(s); error_bdev: - blkdev_put(bdev, mode | FMODE_EXCL); + blkdev_put(bdev, mode); error: return ERR_PTR(error); } @@ -862,6 +862,7 @@ void kill_block_super(struct super_block *sb) bdev->bd_super = NULL; generic_shutdown_super(sb); sync_blockdev(bdev); + WARN_ON_ONCE(!(mode & FMODE_EXCL)); blkdev_put(bdev, mode | FMODE_EXCL); } -- cgit v1.2.2