The 02/15/2021 19:08, Mike Snitzer wrote: > On Mon, Feb 15 2021 at 5:34am -0500, > Sergei Shtepa wrote: > > > The 02/12/2021 19:06, Mike Snitzer wrote: > > > On Fri, Feb 12 2021 at 6:34am -0500, > > > Sergei Shtepa wrote: > > > > > > > The 02/11/2021 20:51, Mike Snitzer wrote: > > > > > On Tue, Feb 09 2021 at 9:30am -0500, > > > > > Sergei Shtepa wrote: > > > > > > > > > > > The 'noexcl' option allow to open underlying block-device > > > > > > without FMODE_EXCL. > > > > > > > > > > > > Signed-off-by: Sergei Shtepa > > > > > > --- > > > > > > 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? > > > > > > > > Of course I explored that kind of approach. The easiest thing to do > > > > is fell back to opening without FMODE_EXCL if FMODE_EXCL open failed. > > > > > > > > But I remind you once again that in this case, without changing > > > > the code of each target, we will change the behavior of each. > > > > Any target will open the device without the FMODE_EXCL flag if the device > > > > is already busy. This can cause errors and cause data loss. > > > > I would not want the device mapper to get worse when adding new functionality. > > > > > > Right, but I'm not talking about a blind fallback that strips FMODE_EXCL > > > if FMODE_EXCL open failed. > > > > > > > I will do so in the next patch, as you are sure that it is better... Or > > > > I'll think about it again and try to suggest a better implementation. > > > > > > > > Thank you, Mike. > > > > > > > > > > > > > > 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. > > > > > > I'm suggesting that open_table_device and close_table_device be made > > > aware of the fact that they are operating on behalf of your remap ioctl > > > (interpose). So store state in the mapped_device that reflects a remap > > > was used. > > > > > > Still clunky but at least it confines it to an implementation detail > > > managed by DM core rather than imposing awkward interface changes in > > > both DM core and the DM targets. > > > > > > Mike > > > > > > > Based on your requirements, I conclude that the knowledge about the use > > of interposer should be passed when creating target, since this is where > > the open_table_device function is called. > > This means that the 'noexcl' parameter is no longer needed, but will be > > replaced with 'interposer'. > > The ioctl is no longer needed, the target already knows that it works > > through the interposer, and we can attach it already when creating > > the target. > > > > I like this logic, and I will implement it. > > Yes, I never understood why a new ioctl was introduced. But please be > aware that this should _not_ be implemented in terms of each DM target > needing to handle 'interposer' being passed as a text arg to the .ctr(). > > It should be an optional DM_INTERPOSER_FLAG added to DM_DEV_CREATE_CMD > (much like optional DM_NOFLUSH_FLAG can be used with DM_DEV_SUSPEND_CMD). > > Mike > Hello, Mike. I tried to do as you specified and I think I succeeded. Before sending the next version of the patch, I would like to suggest that you see if I am moving in the right direction. I _attach_ the patches for the DM to the email. The first one is nothing particularly new, I just put the code for blk_interposer in the dm-interposer.c/.h file. In the second one, I implemented the DM_INTERPOSED_DEV_FLAG flag. No one of the targets were changed. I haven't run this code yet. To do this, I need to further refine dmsetup. This is in progress. But I think the code looks good. -- Sergei Shtepa Veeam Software developer.