| Message ID | 20200812140436.11749-1-nborisov@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: Document some invariants of seed code | expand |
On Wed, Aug 12, 2020 at 05:04:36PM +0300, Nikolay Borisov wrote: > Without good understanding of how seed devices works it's hard to grok > some of what the code in open_seed_devices or btrfs_prepare_sprout does. > > Add comments hopefully reducing some of the cognitive load. > > Signed-off-by: Nikolay Borisov <nborisov@suse.com> I'll add this patch to the seed list api patchset.
On 12/8/20 10:04 pm, Nikolay Borisov wrote: > Without good understanding of how seed devices works it's hard to grok > some of what the code in open_seed_devices or btrfs_prepare_sprout does. > > Add comments hopefully reducing some of the cognitive load. > > Signed-off-by: Nikolay Borisov <nborisov@suse.com> > --- > fs/btrfs/volumes.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 631cb03b3513..f7ee7837e6bc 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -2361,10 +2361,20 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info) > if (!fs_devices->seeding) > return -EINVAL; > > + /* > + * Private copy of the seed devices, anchored at > + * fs_info->fs_devices->seed_list > + */ > seed_devices = alloc_fs_devices(NULL, NULL); > if (IS_ERR(seed_devices)) > return PTR_ERR(seed_devices); > > + /* > + * It's necessary to retain a copy of the original seed fs_devices in > + * fs_uuids so that filesystems which have been seeded can be > + * successfully reference the seed device from open_seed_devices. This > + * also supports multiple fs seed. > + */ > > old_devices = clone_fs_devices(fs_devices); > if (IS_ERR(old_devices)) { > kfree(seed_devices); > @@ -6713,6 +6723,7 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info, > lockdep_assert_held(&uuid_mutex); > ASSERT(fsid); > > + /* This will match only for multi-device seed fs */ > list_for_each_entry(fs_devices, &fs_info->fs_devices->seed_list, seed_list) > if (!memcmp(fs_devices->fsid, fsid, BTRFS_FSID_SIZE)) > return fs_devices; > @@ -6732,6 +6743,10 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info, > return fs_devices; > } > > + /* > + * Upon first call for a seed fs fsid just create a private copy of the > + * respective fs_devices and anchor it at fs_info->fs_devices->seed_list > + */ > fs_devices = clone_fs_devices(fs_devices); > if (IS_ERR(fs_devices)) > return fs_devices; > Looks good. Thanks Reviewed-by: Anand Jain <anand.jain@oracle.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 631cb03b3513..f7ee7837e6bc 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2361,10 +2361,20 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info) if (!fs_devices->seeding) return -EINVAL; + /* + * Private copy of the seed devices, anchored at + * fs_info->fs_devices->seed_list + */ seed_devices = alloc_fs_devices(NULL, NULL); if (IS_ERR(seed_devices)) return PTR_ERR(seed_devices); + /* + * It's necessary to retain a copy of the original seed fs_devices in + * fs_uuids so that filesystems which have been seeded can be + * successfully reference the seed device from open_seed_devices. This + * also supports multiple fs seed. + */ old_devices = clone_fs_devices(fs_devices); if (IS_ERR(old_devices)) { kfree(seed_devices); @@ -6713,6 +6723,7 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info, lockdep_assert_held(&uuid_mutex); ASSERT(fsid); + /* This will match only for multi-device seed fs */ list_for_each_entry(fs_devices, &fs_info->fs_devices->seed_list, seed_list) if (!memcmp(fs_devices->fsid, fsid, BTRFS_FSID_SIZE)) return fs_devices; @@ -6732,6 +6743,10 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info, return fs_devices; } + /* + * Upon first call for a seed fs fsid just create a private copy of the + * respective fs_devices and anchor it at fs_info->fs_devices->seed_list + */ fs_devices = clone_fs_devices(fs_devices); if (IS_ERR(fs_devices)) return fs_devices;
Without good understanding of how seed devices works it's hard to grok some of what the code in open_seed_devices or btrfs_prepare_sprout does. Add comments hopefully reducing some of the cognitive load. Signed-off-by: Nikolay Borisov <nborisov@suse.com> --- fs/btrfs/volumes.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)