Utilize per-vma locks to stabilize vma after lookup without taking mmap_lock during PROCMAP_QUERY ioctl execution. While we might take mmap_lock for reading during contention, we do that momentarily only to lock the vma. This change is designed to reduce mmap_lock contention and prevent PROCMAP_QUERY ioctl calls from blocking address space updates.
Signed-off-by: Suren Baghdasaryan surenb@google.com Acked-by: Andrii Nakryiko andrii@kernel.org --- fs/proc/task_mmu.c | 60 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 48 insertions(+), 12 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index ff3fe488ce51..0496d5969a51 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -487,28 +487,64 @@ static int pid_maps_open(struct inode *inode, struct file *file) PROCMAP_QUERY_VMA_FLAGS \ )
-static int query_vma_setup(struct mm_struct *mm) +#ifdef CONFIG_PER_VMA_LOCK + +static int query_vma_setup(struct proc_maps_private *priv) { - return mmap_read_lock_killable(mm); + priv->locked_vma = NULL; + priv->mmap_locked = false; + + return 0; }
-static void query_vma_teardown(struct mm_struct *mm, struct vm_area_struct *vma) +static void query_vma_teardown(struct proc_maps_private *priv) { - mmap_read_unlock(mm); + unlock_vma(priv); +} + +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_private *priv, + unsigned long addr) +{ + struct vm_area_struct *vma; + + rcu_read_lock(); + vma_iter_init(&priv->iter, priv->mm, addr); + vma = get_next_vma(priv, addr); + rcu_read_unlock(); + + return vma; }
-static struct vm_area_struct *query_vma_find_by_addr(struct mm_struct *mm, unsigned long addr) +#else /* CONFIG_PER_VMA_LOCK */ + +static int query_vma_setup(struct proc_maps_private *priv) { - return find_vma(mm, addr); + return mmap_read_lock_killable(priv->mm); }
-static struct vm_area_struct *query_matching_vma(struct mm_struct *mm, +static void query_vma_teardown(struct proc_maps_private *priv) +{ + mmap_read_unlock(priv->mm); +} + +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_private *priv, + unsigned long addr) +{ + return find_vma(priv->mm, addr); +} + +#endif /* CONFIG_PER_VMA_LOCK */ + +static struct vm_area_struct *query_matching_vma(struct proc_maps_private *priv, unsigned long addr, u32 flags) { struct vm_area_struct *vma;
next_vma: - vma = query_vma_find_by_addr(mm, addr); + vma = query_vma_find_by_addr(priv, addr); + if (IS_ERR(vma)) + return vma; + if (!vma) goto no_vma;
@@ -584,13 +620,13 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) if (!mm || !mmget_not_zero(mm)) return -ESRCH;
- err = query_vma_setup(mm); + err = query_vma_setup(priv); if (err) { mmput(mm); return err; }
- vma = query_matching_vma(mm, karg.query_addr, karg.query_flags); + vma = query_matching_vma(priv, karg.query_addr, karg.query_flags); if (IS_ERR(vma)) { err = PTR_ERR(vma); vma = NULL; @@ -675,7 +711,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) }
/* unlock vma or mmap_lock, and put mm_struct before copying data to user */ - query_vma_teardown(mm, vma); + query_vma_teardown(priv); mmput(mm);
if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr), @@ -695,7 +731,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) return 0;
out: - query_vma_teardown(mm, vma); + query_vma_teardown(priv); mmput(mm); kfree(name_buf); return err;