Re: [PATCH v5 5/6] dm: add 'noexcl' option for dm-linear
From: Mike Snitzer <hidden>
Date: 2021-02-11 18:30:11
Also in:
dm-devel, linux-doc, lkml
On Tue, Feb 09 2021 at 9:30am -0500, Sergei Shtepa [off-list ref] wrote:
quoted hunk ↗ jump to hunk
The 'noexcl' option allow to open underlying block-device without FMODE_EXCL. Signed-off-by: Sergei Shtepa <redacted> --- drivers/md/dm-linear.c | 14 +++++++++++++- drivers/md/dm-table.c | 14 ++++++++------ drivers/md/dm.c | 26 +++++++++++++++++++------- drivers/md/dm.h | 2 +- include/linux/device-mapper.h | 7 +++++++ 5 files changed, 48 insertions(+), 15 deletions(-)diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c index 00774b5d7668..b16d89802b9d 100644 --- a/drivers/md/dm-linear.c +++ b/drivers/md/dm-linear.c@@ -33,7 +33,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv) char dummy; int ret; - if (argc != 2) { + if ((argc < 2) || (argc > 3)) { ti->error = "Invalid argument count"; return -EINVAL; }@@ -51,6 +51,18 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv) } lc->start = tmp; + ti->non_exclusive = false; + if (argc > 2) { + if (strcmp("noexcl", argv[2]) == 0) + ti->non_exclusive = true; + else if (strcmp("excl", argv[2]) == 0) + ti->non_exclusive = false; + else { + ti->error = "Invalid exclusive option"; + return -EINVAL; + } + } + ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev); if (ret) { ti->error = "Device lookup failed";diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 4acf2342f7ad..f020459465bd 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c@@ -322,7 +322,7 @@ static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev, * device and not to touch the existing bdev field in case * it is accessed concurrently. */ -static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode, +static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode, bool non_exclusive, struct mapped_device *md) { int r;@@ -330,8 +330,8 @@ static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode, old_dev = dd->dm_dev; - r = dm_get_table_device(md, dd->dm_dev->bdev->bd_dev, - dd->dm_dev->mode | new_mode, &new_dev); + r = dm_get_table_device(md, dd->dm_dev->bdev->bd_dev, dd->dm_dev->mode | new_mode, + non_exclusive, &new_dev); if (r) return r;@@ -387,7 +387,8 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, if (!dd) return -ENOMEM; - if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) { + r = dm_get_table_device(t->md, dev, mode, ti->non_exclusive, &dd->dm_dev); + if (r) { kfree(dd); return r; }@@ -396,8 +397,9 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, list_add(&dd->list, &t->devices); goto out; - } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { - r = upgrade_mode(dd, mode, t->md); + } else if ((dd->dm_dev->mode != (mode | dd->dm_dev->mode)) && + (dd->dm_dev->non_exclusive != ti->non_exclusive)) { + r = upgrade_mode(dd, mode, ti->non_exclusive, t->md); if (r) return r; }diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 00c41aa6d092..c25dcc2fdb89 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c@@ -1117,33 +1117,44 @@ static void close_table_device(struct table_device *td, struct mapped_device *md if (!td->dm_dev.bdev) return; - bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md)); - blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL); + if (td->dm_dev.non_exclusive) + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode); + else { + bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md)); + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL); + } + + + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode); + put_dax(td->dm_dev.dax_dev); td->dm_dev.bdev = NULL; td->dm_dev.dax_dev = NULL; + td->dm_dev.non_exclusive = false; } static struct table_device *find_table_device(struct list_head *l, dev_t dev, - fmode_t mode) + fmode_t mode, bool non_exclusive) { struct table_device *td; list_for_each_entry(td, l, list) - if (td->dm_dev.bdev->bd_dev == dev && td->dm_dev.mode == mode) + if (td->dm_dev.bdev->bd_dev == dev && + td->dm_dev.mode == mode && + td->dm_dev.non_exclusive == non_exclusive) return td; return NULL; } -int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, +int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, bool non_exclusive, struct dm_dev **result) { int r; struct table_device *td; mutex_lock(&md->table_devices_lock); - td = find_table_device(&md->table_devices, dev, mode); + td = find_table_device(&md->table_devices, dev, mode, non_exclusive); if (!td) { td = kmalloc_node(sizeof(*td), GFP_KERNEL, md->numa_node_id); if (!td) {@@ -1154,7 +1165,8 @@ int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, td->dm_dev.mode = mode; td->dm_dev.bdev = NULL; - if ((r = open_table_device(td, dev, md))) { + r = open_table_device(td, dev, md, non_exclusive); + if (r) { mutex_unlock(&md->table_devices_lock); kfree(td); return r;diff --git a/drivers/md/dm.h b/drivers/md/dm.h index fffe1e289c53..7bf20fb2de74 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h@@ -179,7 +179,7 @@ int dm_open_count(struct mapped_device *md); int dm_lock_for_deletion(struct mapped_device *md, bool mark_deferred, bool only_deferred); int dm_cancel_deferred_remove(struct mapped_device *md); int dm_request_based(struct mapped_device *md); -int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, +int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, bool non_exclusive, struct dm_dev **result); void dm_put_table_device(struct mapped_device *md, struct dm_dev *d);diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 61a66fb8ebb3..70002363bfc0 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h@@ -150,6 +150,7 @@ struct dm_dev { struct block_device *bdev; struct dax_device *dax_dev; fmode_t mode; + bool non_exclusive; char name[16]; };@@ -325,6 +326,12 @@ struct dm_target { * whether or not its underlying devices have support. */ bool discards_supported:1; + + /* + * Set if this target needs to open device without FMODE_EXCL + * mode. + */ + bool non_exclusive:1; }; void *dm_per_bio_data(struct bio *bio, size_t data_size);-- 2.20.1
I'm really not liking this tug-of-war about FMODE_EXCL vs not. Especially dislike the prospect of needing to change _every_ DM target that would be made to support blk_interposer. I've said this before, private or otherwise, but: Hannes' approach that fell back to opening without FMODE_EXCL if FMODE_EXCL open failed. Have you explored that kind of approach? You _should_ be able to infer that interposer is being used given the requirement to use an explicit remap ioctl to establish the use of interposer. Mike