The patch titled
Subject: kernel: better document the use_mm/unuse_mm API contract
has been added to the -mm tree. Its filename is
kernel-better-document-the-use_mm-unuse_mm-api-contract.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-better-document-the-use_mm-unuse_mm-api-contract.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-better-document-the-use_mm-unuse_mm-api-contract.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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------------------------------------------------------
From: Christoph Hellwig <hch@xxxxxx>
Subject: kernel: better document the use_mm/unuse_mm API contract
Switch the function documentation to kerneldoc comments, and add
WARN_ON_ONCE asserts that the calling thread is a kernel thread and does
not have ->mm set (or has ->mm set in the case of unuse_mm).
Also give the functions a kthread_ prefix to better document the use case.
Link: http://lkml.kernel.org/r/20200404094101.672954-6-hch@xxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Felipe Balbi <balbi@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
Cc: Zhi Wang <zhi.a.wang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h | 4 +-
drivers/gpu/drm/i915/gvt/kvmgt.c | 4 +-
drivers/usb/gadget/function/f_fs.c | 4 +-
drivers/usb/gadget/legacy/inode.c | 4 +-
drivers/vhost/vhost.c | 4 +-
fs/io-wq.c | 6 +--
fs/io_uring.c | 6 +--
include/linux/kthread.h | 4 +-
kernel/kthread.c | 33 +++++++++----------
mm/oom_kill.c | 6 +--
mm/vmacache.c | 4 +-
11 files changed, 39 insertions(+), 40 deletions(-)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
@@ -192,9 +192,9 @@ uint8_t amdgpu_amdkfd_get_xgmi_hops_coun
if ((mmptr) == current->mm) { \
valid = !get_user((dst), (wptr)); \
} else if (current->flags & PF_KTHREAD) { \
- use_mm(mmptr); \
+ kthread_use_mm(mmptr); \
valid = !get_user((dst), (wptr)); \
- unuse_mm(mmptr); \
+ kthread_unuse_mm(mmptr); \
} \
pagefault_enable(); \
} \
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -2048,7 +2048,7 @@ static int kvmgt_rw_gpa(unsigned long ha
if (kthread) {
if (!mmget_not_zero(kvm->mm))
return -EFAULT;
- use_mm(kvm->mm);
+ kthread_use_mm(kvm->mm);
}
idx = srcu_read_lock(&kvm->srcu);
@@ -2057,7 +2057,7 @@ static int kvmgt_rw_gpa(unsigned long ha
srcu_read_unlock(&kvm->srcu, idx);
if (kthread) {
- unuse_mm(kvm->mm);
+ kthread_unuse_mm(kvm->mm);
mmput(kvm->mm);
}
--- a/drivers/usb/gadget/function/f_fs.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/drivers/usb/gadget/function/f_fs.c
@@ -827,9 +827,9 @@ static void ffs_user_copy_worker(struct
mm_segment_t oldfs = get_fs();
set_fs(USER_DS);
- use_mm(io_data->mm);
+ kthread_use_mm(io_data->mm);
ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data);
- unuse_mm(io_data->mm);
+ kthread_unuse_mm(io_data->mm);
set_fs(oldfs);
}
--- a/drivers/usb/gadget/legacy/inode.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/drivers/usb/gadget/legacy/inode.c
@@ -462,9 +462,9 @@ static void ep_user_copy_worker(struct w
struct kiocb *iocb = priv->iocb;
size_t ret;
- use_mm(mm);
+ kthread_use_mm(mm);
ret = copy_to_iter(priv->buf, priv->actual, &priv->to);
- unuse_mm(mm);
+ kthread_unuse_mm(mm);
if (!ret)
ret = -EFAULT;
--- a/drivers/vhost/vhost.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/drivers/vhost/vhost.c
@@ -332,7 +332,7 @@ static int vhost_worker(void *data)
mm_segment_t oldfs = get_fs();
set_fs(USER_DS);
- use_mm(dev->mm);
+ kthread_use_mm(dev->mm);
for (;;) {
/* mb paired w/ kthread_stop */
@@ -360,7 +360,7 @@ static int vhost_worker(void *data)
schedule();
}
}
- unuse_mm(dev->mm);
+ kthread_unuse_mm(dev->mm);
set_fs(oldfs);
return 0;
}
--- a/fs/io_uring.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/fs/io_uring.c
@@ -5876,7 +5876,7 @@ fail_req:
err = -EFAULT;
goto fail_req;
}
- use_mm(ctx->sqo_mm);
+ kthread_use_mm(ctx->sqo_mm);
*mm = ctx->sqo_mm;
}
@@ -5948,7 +5948,7 @@ static int io_sq_thread(void *data)
* may sleep.
*/
if (cur_mm) {
- unuse_mm(cur_mm);
+ kthread_unuse_mm(cur_mm);
mmput(cur_mm);
cur_mm = NULL;
}
@@ -6025,7 +6025,7 @@ static int io_sq_thread(void *data)
set_fs(old_fs);
if (cur_mm) {
- unuse_mm(cur_mm);
+ kthread_unuse_mm(cur_mm);
mmput(cur_mm);
}
revert_creds(old_cred);
--- a/fs/io-wq.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/fs/io-wq.c
@@ -170,7 +170,7 @@ static bool __io_worker_unuse(struct io_
}
__set_current_state(TASK_RUNNING);
set_fs(KERNEL_DS);
- unuse_mm(worker->mm);
+ kthread_unuse_mm(worker->mm);
mmput(worker->mm);
worker->mm = NULL;
}
@@ -417,7 +417,7 @@ static struct io_wq_work *io_get_next_wo
static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work)
{
if (worker->mm) {
- unuse_mm(worker->mm);
+ kthread_unuse_mm(worker->mm);
mmput(worker->mm);
worker->mm = NULL;
}
@@ -426,7 +426,7 @@ static void io_wq_switch_mm(struct io_wo
return;
}
if (mmget_not_zero(work->mm)) {
- use_mm(work->mm);
+ kthread_use_mm(work->mm);
if (!worker->mm)
set_fs(USER_DS);
worker->mm = work->mm;
--- a/include/linux/kthread.h~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/include/linux/kthread.h
@@ -200,8 +200,8 @@ bool kthread_cancel_delayed_work_sync(st
void kthread_destroy_worker(struct kthread_worker *worker);
-void use_mm(struct mm_struct *mm);
-void unuse_mm(struct mm_struct *mm);
+void kthread_use_mm(struct mm_struct *mm);
+void kthread_unuse_mm(struct mm_struct *mm);
struct cgroup_subsys_state;
--- a/kernel/kthread.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/kernel/kthread.c
@@ -1208,18 +1208,18 @@ void kthread_destroy_worker(struct kthre
}
EXPORT_SYMBOL(kthread_destroy_worker);
-/*
- * use_mm
- * Makes the calling kernel thread take on the specified
- * mm context.
- * (Note: this routine is intended to be called only
- * from a kernel thread context)
+/**
+ * kthread_use_mm - make the calling kthread operate on an address space
+ * @mm: address space to operate on
*/
-void use_mm(struct mm_struct *mm)
+void kthread_use_mm(struct mm_struct *mm)
{
struct mm_struct *active_mm;
struct task_struct *tsk = current;
+ WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
+ WARN_ON_ONCE(tsk->mm);
+
task_lock(tsk);
active_mm = tsk->active_mm;
if (active_mm != mm) {
@@ -1236,20 +1236,19 @@ void use_mm(struct mm_struct *mm)
if (active_mm != mm)
mmdrop(active_mm);
}
-EXPORT_SYMBOL_GPL(use_mm);
+EXPORT_SYMBOL_GPL(kthread_use_mm);
-/*
- * unuse_mm
- * Reverses the effect of use_mm, i.e. releases the
- * specified mm context which was earlier taken on
- * by the calling kernel thread
- * (Note: this routine is intended to be called only
- * from a kernel thread context)
+/**
+ * kthread_use_mm - reverse the effect of kthread_use_mm()
+ * @mm: address space to operate on
*/
-void unuse_mm(struct mm_struct *mm)
+void kthread_unuse_mm(struct mm_struct *mm)
{
struct task_struct *tsk = current;
+ WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
+ WARN_ON_ONCE(!tsk->mm);
+
task_lock(tsk);
sync_mm_rss(mm);
tsk->mm = NULL;
@@ -1257,7 +1256,7 @@ void unuse_mm(struct mm_struct *mm)
enter_lazy_tlb(mm, tsk);
task_unlock(tsk);
}
-EXPORT_SYMBOL_GPL(unuse_mm);
+EXPORT_SYMBOL_GPL(kthread_unuse_mm);
#ifdef CONFIG_BLK_CGROUP
/**
--- a/mm/oom_kill.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/mm/oom_kill.c
@@ -126,7 +126,7 @@ static bool oom_cpuset_eligible(struct t
/*
* The process p may have detached its own ->mm while exiting or through
- * use_mm(), but one or more of its subthreads may still have a valid
+ * kthread_use_mm(), but one or more of its subthreads may still have a valid
* pointer. Return p, or any of its subthreads with a valid ->mm, with
* task_lock() held.
*/
@@ -919,8 +919,8 @@ static void __oom_kill_process(struct ta
continue;
}
/*
- * No use_mm() user needs to read from the userspace so we are
- * ok to reap it.
+ * No kthead_use_mm() user needs to read from the userspace so
+ * we are ok to reap it.
*/
if (unlikely(p->flags & PF_KTHREAD))
continue;
--- a/mm/vmacache.c~kernel-better-document-the-use_mm-unuse_mm-api-contract
+++ a/mm/vmacache.c
@@ -25,8 +25,8 @@
* task's vmacache pertains to a different mm (ie, its own). There is
* nothing we can do here.
*
- * Also handle the case where a kernel thread has adopted this mm via use_mm().
- * That kernel thread's vmacache is not applicable to this mm.
+ * Also handle the case where a kernel thread has adopted this mm via
+ * kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
*/
static inline bool vmacache_valid_mm(struct mm_struct *mm)
{
_
Patches currently in -mm which might be from hch@xxxxxx are
x86-hyperv-use-vmalloc_exec-for-the-hypercall-page.patch
x86-fix-vmap-arguments-in-map_irq_stack.patch
staging-android-ion-use-vmap-instead-of-vm_map_ram.patch
staging-media-ipu3-use-vmap-instead-of-reimplementing-it.patch
dma-mapping-use-vmap-insted-of-reimplementing-it.patch
powerpc-add-an-ioremap_phb-helper.patch
powerpc-remove-__ioremap_at-and-__iounmap_at.patch
mm-remove-__get_vm_area.patch
mm-unexport-unmap_kernel_range_noflush.patch
mm-rename-config_pgtable_mapping-to-config_zsmalloc_pgtable_mapping.patch
mm-only-allow-page-table-mappings-for-built-in-zsmalloc.patch
mm-pass-addr-as-unsigned-long-to-vb_free.patch
mm-remove-vmap_page_range_noflush-and-vunmap_page_range.patch
mm-rename-vmap_page_range-to-map_kernel_range.patch
mm-dont-return-the-number-of-pages-from-map_kernel_range_noflush.patch
mm-remove-map_vm_range.patch
mm-remove-unmap_vmap_area.patch
mm-remove-the-prot-argument-from-vm_map_ram.patch
mm-enforce-that-vmap-cant-map-pages-executable.patch
gpu-drm-remove-the-powerpc-hack-in-drm_legacy_sg_alloc.patch
mm-remove-the-pgprot-argument-to-__vmalloc.patch
mm-remove-the-prot-argument-to-__vmalloc_node.patch
mm-remove-both-instances-of-__vmalloc_node_flags.patch
mm-remove-__vmalloc_node_flags_caller.patch
mm-switch-the-test_vmalloc-module-to-use-__vmalloc_node.patch
mm-remove-vmalloc_user_node_flags.patch
arm64-use-__vmalloc_node-in-arch_alloc_vmap_stack.patch
powerpc-use-__vmalloc_node-in-alloc_vm_stack.patch
s390-use-__vmalloc_node-in-stack_alloc.patch
amdgpu-a-null-mm-does-not-mean-a-thread-is-a-kthread.patch
i915-gvt-kvm-a-null-mm-does-not-mean-a-thread-is-a-kthread.patch
i915-gvt-remove-unused-xen-bits.patch
kernel-move-use_mm-unuse_mm-to-kthreadc.patch
kernel-better-document-the-use_mm-unuse_mm-api-contract.patch
kernel-set-user_ds-in-kthread_use_mm.patch
