user/sven/linux.git/fs/pnode.c, branch v6.17.6

change_mnt_propagation(): calculate propagation source only if we'll need it

2025-08-19T16:05:59Z

We only need it when mount in question was sending events downstream (then recepients need to switch to new master) or the mount is being turned into slave (then we need a new master for it). That wouldn't be a big deal, except that it causes quite a bit of work when umount_tree() is taking a large peer group out. Adding a trivial "don't bother calling propagation_source() unless we are going to use its results" logics improves the things quite a bit. We are still doing unnecessary work on bulk removals from propagation graph, but the full solution for that will have to wait for the next merge window. Fixes: 955336e204ab "do_make_slave(): choose new master sanely" Reviewed-by: Christian Brauner Signed-off-by: Al Viro

propagate_umount(): only surviving overmounts should be reparented

2025-08-19T16:00:07Z

... as the comments in reparent() clearly say. As it is, we reparent *all* overmounts of the mounts being taken out, including those that are taken out themselves. It's not only a potentially massive slowdown (on a pathological setup we might end up with O(N^2) time for N mounts being kicked out), it can end up with incorrect ->overmount in the surviving mounts. Fixes: f0d0ba19985d "Rewrite of propagate_umount()" Reviewed-by: Christian Brauner Signed-off-by: Al Viro

copy_tree(): don't link the mounts via mnt_list

2025-06-29T23:03:37Z

The only place that really needs to be adjusted is commit_tree() - there we need to iterate through the copy and we might as well use next_mnt() for that. However, in case when our tree has been slid under something already mounted (propagation to a mountpoint that already has something mounted on it or a 'beneath' move_mount) we need to take care not to walk into the overmounting tree. Signed-off-by: Al Viro

change_mnt_propagation(): move ->mnt_master assignment into MS_SLAVE case

2025-06-29T23:03:30Z

Signed-off-by: Al Viro

mnt_slave_list/mnt_slave: turn into hlist_head/hlist_node

2025-06-29T23:03:30Z

Signed-off-by: Al Viro

turn do_make_slave() into transfer_propagation()

2025-06-29T23:03:30Z

Lift calculation of replacement propagation source, removal from peer group and assignment of ->mnt_master from do_make_slave() into change_mnt_propagation() itself. What remains is switching of what used to get propagation *through* mnt to alternative source. Rename to transfer_propagation(), passing it the replacement source as the second argument. Have it return void, while we are at it. Signed-off-by: Al Viro

do_make_slave(): choose new master sanely

2025-06-29T23:03:30Z

When mount changes propagation type so that it doesn't propagate events any more (MS_PRIVATE, MS_SLAVE, MS_UNBINDABLE), we need to make sure that event propagation between other mounts is unaffected. We need to make sure that events from peers and master of that mount (if any) still reach everything that used to be on its ->mnt_slave_list. If mount has neither peers nor master, we simply need to dissolve its ->mnt_slave_list and clear ->mnt_master of everything in there. If mount has peers, we transfer everything in ->mnt_slave_list of this mount into that of some of those peers (and adjust ->mnt_master accordingly). If mount has a master but no peers, we transfer everything in ->mnt_slave_list of this mount into that of its master (adjusting ->mnt_master, etc.). There are two problems with the current implementation: * there's a long-obsolete logics in choosing the peer - once upon a time it made sense to prefer the peer that had the same ->mnt_root as our mount, but that had been pointless since 2014 ("smarter propagate_mnt()") * the most common caller of that thing is umount_tree() taking the mounts out of propagation graph. In that case it's possible to have ->mnt_slave_list contents moved many times, since the replacement master is likely to be taken out by the same umount_tree(), etc. Take the choice of replacement master into a separate function (propagation_source()) and teach it to skip the candidates that are going to be taken out. Signed-off-by: Al Viro

change_mnt_propagation(): do_make_slave() is a no-op unless IS_MNT_SHARED()

2025-06-29T23:03:30Z

... since mnt->mnt_share and mnt->mnt_slave_list are guaranteed to be empty unless IS_MNT_SHARED(mnt). Signed-off-by: Al Viro

change_mnt_propagation() cleanups, step 1

2025-06-29T23:03:30Z

Lift changing ->mnt_slave from do_make_slave() into the caller. Simplifies the next steps... Signed-off-by: Al Viro

propagate_mnt(): fix comment and convert to kernel-doc, while we are at it

2025-06-29T23:03:30Z

Mountpoint is passed as struct mountpoint *, not struct dentry * (and called dest_mp, not dest_dentry) since 2013. Roots of created copies are linked via mnt_hash, not mnt_list since a bit before the merge into mainline back in 2005. Signed-off-by: Al Viro