Hi Thanks for the development! I'm already developing something similar paper: http://people.redhat.com/mpatocka/papers/shared-snapshots.pdf kernel code: http://people.redhat.com/mpatocka/patches/kernel/new-snapshots/r22/ user code: http://people.redhat.com/mpatocka/patches/userspace/new-snapshots/lvm-2.02.73/ Please change your code to conform to the existing interface. My kernel code is extendible, you can plug arbitrary on-disk formats to it, there's another example of Daniel Phillips' zumastore snapshots. Use this interface so that it could be used with the existing userspace infrastructure. Mikulas On Wed, 6 Oct 2010, Cong Meng wrote: > Hello everyone, > > I am very glad to introduce my work dm-snap-mv here. > > > what is dm-snap-mv > ------------------- > The dm-snap-mv is a target module for device-mapper, which can take > multiple snapshots against an existing block device(origin device). > > All snapshots are saved in an independent block device(COW device). > > The copy-on-write is used, so only diff-data will be saved in the COW device. > > > features > -------- > 1. snapshot of origin > 2. snapshot of snapshot > 3. instant snapshot creation and deletion > 4. origin and snapshots are concurrent readable/writable > 5. rollback snapshot to origin > 6. multiple origin devices share a COW device > 7. multiple COW devices are supported > > > diagram > ------- > > +---------------------+ +---------------+ +--------------+ > read <--| |----- | | | > | origin dm_dev | | origin_dev | COW | | > write ---| |----> |-----> snapshot-1 | > +---------------------+ +--|------------+ | ... | > | | ... | > +---------------------+ +--|------------------+ ... | > read <--| |-------?- snapshot-N | > | snapshot-X dm_dev | | cow_dev | > write ---| |----> | > +---------------------+ +------------------------------------+ > > dm_dev: device-mapper device, created by "dmsetup create ..." > COW: copy-on-write > > > download the source > ----------------------- > http://github.com/mcpacino/dm-snap-mv > > git clone git://github.com/mcpacino/dm-snap-mv.git > > > a kernel patch > -------------- > Now, dm-snap-mv highly depends on a kernel patch below, which make __getblk() > can get a 4K buffer head while block size of the disk is NOT 4K. > > Signed-off-by: Cong Meng <mcpacino@xxxxxxxxx> > --- > fs/buffer.c | 7 ++----- > 1 files changed, 2 insertions(+), 5 deletions(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 3e7dca2..f7f9d33 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -1051,10 +1051,7 @@ grow_buffers(struct block_device *bdev, sector_t block, int size) > pgoff_t index; > int sizebits; > > - sizebits = -1; > - do { > - sizebits++; > - } while ((size << sizebits) < PAGE_SIZE); > + sizebits = PAGE_CACHE_SHIFT - bdev->bd_inode->i_blkbits; > > index = block >> sizebits; > > @@ -2924,7 +2921,7 @@ int submit_bh(int rw, struct buffer_head * bh) > */ > bio = bio_alloc(GFP_NOIO, 1); > > - bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); > + bio->bi_sector = bh->b_blocknr << (bh->b_bdev->bd_inode->i_blkbits - 9); > bio->bi_bdev = bh->b_bdev; > bio->bi_io_vec[0].bv_page = bh->b_page; > bio->bi_io_vec[0].bv_len = bh->b_size; > > -- > dm-devel mailing list > dm-devel@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/dm-devel > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
