Delegate SEEK_HOLE/SEEK_DATA to device-mapper targets. The new dm_seek_hole_data() callback allows target types to customize behavior. The default implementation treats the target as all data with no holes.
Signed-off-by: Stefan Hajnoczi <[email protected]> --- include/linux/device-mapper.h | 5 +++ drivers/md/dm.c | 68 +++++++++++++++++++++++++++++++++++ 2 files changed, 73 insertions(+) diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 82b2195efaca7..e89ebaab6507a 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -161,6 +161,10 @@ typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, pgoff_t pgoff, typedef size_t (*dm_dax_recovery_write_fn)(struct dm_target *ti, pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i); +/* Like llseek(SEEK_HOLE/SEEK_DATA) */ +typedef loff_t (*dm_seek_hole_data)(struct dm_target *ti, loff_t offset, + int whence); + void dm_error(const char *message); struct dm_dev { @@ -210,6 +214,7 @@ struct target_type { dm_dax_direct_access_fn direct_access; dm_dax_zero_page_range_fn dax_zero_page_range; dm_dax_recovery_write_fn dax_recovery_write; + dm_seek_hole_data seek_hole_data; /* For internal device-mapper use. */ struct list_head list; diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 56aa2a8b9d715..3c921bdbd17fc 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -3167,6 +3167,72 @@ void dm_free_md_mempools(struct dm_md_mempools *pools) kfree(pools); } +/* Default implementation for targets that do not implement the callback */ +static loff_t dm_blk_seek_hole_data_default(loff_t offset, int whence, + loff_t size) +{ + switch (whence) { + case SEEK_DATA: + if ((unsigned long long)offset >= size) + return -ENXIO; + return offset; + case SEEK_HOLE: + if ((unsigned long long)offset >= size) + return -ENXIO; + return size; + default: + return -EINVAL; + } +} + +static loff_t dm_blk_do_seek_hole_data(struct dm_table *table, loff_t offset, + int whence) +{ + struct dm_target *ti; + loff_t end; + + /* Loop when the end of a target is reached */ + do { + ti = dm_table_find_target(table, offset >> SECTOR_SHIFT); + if (!ti) + return whence == SEEK_DATA ? -ENXIO : offset; + + end = (ti->begin + ti->len) << SECTOR_SHIFT; + + if (ti->type->seek_hole_data) + offset = ti->type->seek_hole_data(ti, offset, whence); + else + offset = dm_blk_seek_hole_data_default(offset, whence, end); + + if (whence == SEEK_DATA && offset == -ENXIO) + offset = end; + } while (offset == end); + + return offset; +} + +static loff_t dm_blk_seek_hole_data(struct block_device *bdev, loff_t offset, + int whence) +{ + struct mapped_device *md = bdev->bd_disk->private_data; + struct dm_table *table; + int srcu_idx; + loff_t ret; + + if (dm_suspended_md(md)) + return -EAGAIN; + + table = dm_get_live_table(md, &srcu_idx); + if (!table) + return -EIO; + + ret = dm_blk_do_seek_hole_data(table, offset, whence); + + dm_put_live_table(md, srcu_idx); + + return ret; +} + struct dm_pr { u64 old_key; u64 new_key; @@ -3493,6 +3559,7 @@ static const struct block_device_operations dm_blk_dops = { .getgeo = dm_blk_getgeo, .report_zones = dm_blk_report_zones, .pr_ops = &dm_pr_ops, + .seek_hole_data = dm_blk_seek_hole_data, .owner = THIS_MODULE }; @@ -3502,6 +3569,7 @@ static const struct block_device_operations dm_rq_blk_dops = { .ioctl = dm_blk_ioctl, .getgeo = dm_blk_getgeo, .pr_ops = &dm_pr_ops, + .seek_hole_data = dm_blk_seek_hole_data, .owner = THIS_MODULE }; -- 2.44.0
