diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2025-08-15 15:38:14 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2025-08-19 11:58:18 -0400 |
| commit | 0ddfb62f5d018edcb571a3d8ea30ad5332cf2a69 (patch) | |
| tree | 0ebcb9ab807cebd06512f8ec89956c56c94882c1 | |
| parent | 8742b2d8935f476449ef37e263bc4da3295c7b58 (diff) | |
fix the softlockups in attach_recursive_mnt()
In case when we mounting something on top of a large stack of overmounts,
all of them being peers of each other, we get quadratic time by the
depth of overmount stack. Easily fixed by doing commit_tree() before
reparenting the overmount; simplifies commit_tree() as well - it doesn't
need to skip the already mounted stuff that had been reparented on top
of the new mounts.
Since we are holding mount_lock through both reparenting and call of
commit_tree(), the order does not matter from the mount hash point
of view.
Reported-by: "Lai, Yi" <yi1.lai@linux.intel.com>
Tested-by: "Lai, Yi" <yi1.lai@linux.intel.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: 663206854f02 "copy_tree(): don't link the mounts via mnt_list"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | fs/namespace.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index ddfd4457d338..1c97f93d1865 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1197,10 +1197,7 @@ static void commit_tree(struct mount *mnt) if (!mnt_ns_attached(mnt)) { for (struct mount *m = mnt; m; m = next_mnt(m, mnt)) - if (unlikely(mnt_ns_attached(m))) - m = skip_mnt_tree(m); - else - mnt_add_to_ns(n, m); + mnt_add_to_ns(n, m); n->nr_mounts += n->pending_mounts; n->pending_mounts = 0; } @@ -2704,6 +2701,7 @@ static int attach_recursive_mnt(struct mount *source_mnt, lock_mnt_tree(child); q = __lookup_mnt(&child->mnt_parent->mnt, child->mnt_mountpoint); + commit_tree(child); if (q) { struct mountpoint *mp = root.mp; struct mount *r = child; @@ -2713,7 +2711,6 @@ static int attach_recursive_mnt(struct mount *source_mnt, mp = shorter; mnt_change_mountpoint(r, mp, q); } - commit_tree(child); } unpin_mountpoint(&root); unlock_mount_hash(); |