Hi Alasdair, Thank you for the comments. Alasdair G Kergon wrote:
Make sure you test this properly under low memory situations.
OK.
dm_swap_table() mustn't block waiting for memory to become free (except in a controlled way e.g. with a mempool, but it would need more than that here). Here, dm_swap_table() leads to kmalloc() getting called in sysfs_add_link().
I moved the sysfs_add_link() to the last part of dm_resume(). Directory creation/deletion are also moved in the alloc_dev/ free_dev function as kobject_register/unregister may allocate memory. I didn't change the part of removing symlink as it doesn't allocate memory. Do you think this is an acceptable approach? -- Jun'ichi Nomura, NEC Solutions (America), Inc.
Exporting stacked device relationship to sysfs (dm) Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx> --- linux-2.6.15.orig/drivers/md/dm.c 2006-01-02 22:21:10.000000000 -0500 +++ linux-2.6.15/drivers/md/dm.c 2006-02-17 16:27:38.000000000 -0500 @@ -98,6 +98,12 @@ struct mapped_device { */ struct super_block *frozen_sb; struct block_device *frozen_bdev; + + /* + * sysfs deptree + */ + int sysfs_linked; + struct kobject slave_dir; }; #define MIN_IOS 256 @@ -791,6 +797,7 @@ static struct mapped_device *alloc_dev(u md->disk->private_data = md; sprintf(md->disk->disk_name, "dm-%d", minor); add_disk(md->disk); + stackdev_init(&md->slave_dir, &md->disk->kobj); atomic_set(&md->pending, 0); init_waitqueue_head(&md->wait); @@ -815,6 +822,7 @@ static void free_dev(struct mapped_devic free_minor(md->disk->first_minor); mempool_destroy(md->tio_pool); mempool_destroy(md->io_pool); + stackdev_clear(&md->slave_dir); del_gendisk(md->disk); put_disk(md->disk); blk_put_queue(md->queue); @@ -841,6 +849,42 @@ static void __set_size(struct mapped_dev up(&md->frozen_bdev->bd_inode->i_sem); } +/* create sysfs symlinks between mapped device and underlying devices */ +static int __link_device(struct mapped_device *md, struct dm_table *t) +{ + struct list_head *d, *devices; + + if (md->sysfs_linked) + return 0; + + devices = dm_table_get_devices(t); + for (d = devices->next; d != devices; d = d->next) { + struct dm_dev *dd = list_entry(d, struct dm_dev, list); + stackdev_link(dd->bdev, &md->slave_dir, &md->disk->kobj); + } + + md->sysfs_linked = 1; + return 0; +} + +/* remove sysfs symlinks between mapped device and underlying devices */ +static int __unlink_device(struct mapped_device *md, struct dm_table *t) +{ + struct list_head *d, *devices; + + if (!md->sysfs_linked) + return 0; + + devices = dm_table_get_devices(t); + for (d = devices->next; d != devices; d = d->next) { + struct dm_dev *dd = list_entry(d, struct dm_dev, list); + stackdev_unlink(dd->bdev, &md->slave_dir, &md->disk->kobj); + } + + md->sysfs_linked = 0; + return 0; +} + static int __bind(struct mapped_device *md, struct dm_table *t) { request_queue_t *q = md->queue; @@ -873,6 +917,7 @@ static void __unbind(struct mapped_devic write_lock(&md->map_lock); md->map = NULL; write_unlock(&md->map_lock); + __unlink_device(md, map); dm_table_put(map); } @@ -1139,6 +1184,8 @@ int dm_resume(struct mapped_device *md) dm_table_unplug_all(map); + __link_device(md, map); + r = 0; out:
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