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kernel: better document the use_mm/unuse_mm API contract

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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.

[hch@lst.de: fix a comment typo, cover the newly merged use_mm/unuse_mm caller in vfio]
  Link: http://lkml.kernel.org/r/20200416053158.586887-3-hch@lst.de
[sfr@canb.auug.org.au: powerpc/vas: fix up for {un}use_mm() rename]
  Link: http://lkml.kernel.org/r/20200422163935.5aa93ba5@canb.auug.org.au

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [usb]
Acked-by: Haren Myneni <haren@linux.ibm.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Link: http://lkml.kernel.org/r/20200404094101.672954-6-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2020-06-10 18:42:06 -07:00 committed by Linus Torvalds
parent 4dbe59a6ae
commit f5678e7f2a
12 changed files with 40 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/platforms/powernv/vas-fault.c
View File

@ -127,7 +127,7 @@ static void update_csb(struct vas_window *window,
return;
}
use_mm(window->mm);
kthread_use_mm(window->mm);
rc = copy_to_user(csb_addr, &csb, sizeof(csb));
/*
* User space polls on csb.flags (first byte). So add barrier
@ -139,7 +139,7 @@ static void update_csb(struct vas_window *window,
smp_mb();
rc = copy_to_user(csb_addr, &csb, sizeof(u8));
}
unuse_mm(window->mm);
kthread_unuse_mm(window->mm);
put_task_struct(tsk);
/* Success */

4
drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
View File

@ -197,9 +197,9 @@ uint8_t amdgpu_amdkfd_get_xgmi_hops_count(struct kgd_dev *dst, struct kgd_dev *s
if ((mmptr) == current->mm) { \
valid = !get_user((dst), (wptr)); \
} else if (current->mm == NULL) { \
use_mm(mmptr); \
kthread_use_mm(mmptr); \
valid = !get_user((dst), (wptr)); \
unuse_mm(mmptr); \
kthread_unuse_mm(mmptr); \
} \
pagefault_enable(); \
} \

4
drivers/usb/gadget/function/f_fs.c
View File

@ -827,9 +827,9 @@ static void ffs_user_copy_worker(struct work_struct *work)
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);
}

4
drivers/usb/gadget/legacy/inode.c
View File

@ -462,9 +462,9 @@ static void ep_user_copy_worker(struct work_struct *work)
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;

4
drivers/vfio/vfio_iommu_type1.c
View File

@ -2817,7 +2817,7 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
return -EPERM;
if (kthread)
use_mm(mm);
kthread_use_mm(mm);
else if (current->mm != mm)
goto out;
@ -2844,7 +2844,7 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
*copied = copy_from_user(data, (void __user *)vaddr,
count) ? 0 : count;
if (kthread)
unuse_mm(mm);
kthread_unuse_mm(mm);
out:
mmput(mm);
return *copied ? 0 : -EFAULT;

4
drivers/vhost/vhost.c
View File

@ -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;
}

6
fs/io-wq.c
View File

@ -170,7 +170,7 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
}
__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_work(struct io_wqe *wqe)
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_worker *worker, struct io_wq_work *work)
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;

4
fs/io_uring.c
View File

@ -5866,7 +5866,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
if (io_op_defs[req->opcode].needs_mm && !current->mm) {
if (unlikely(!mmget_not_zero(ctx->sqo_mm)))
return -EFAULT;
use_mm(ctx->sqo_mm);
kthread_use_mm(ctx->sqo_mm);
}
sqe_flags = READ_ONCE(sqe->flags);
@ -5980,7 +5980,7 @@ static inline void io_sq_thread_drop_mm(struct io_ring_ctx *ctx)
struct mm_struct *mm = current->mm;
if (mm) {
unuse_mm(mm);
kthread_unuse_mm(mm);
mmput(mm);
}
}

4
include/linux/kthread.h
View File

@ -200,8 +200,8 @@ bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *work);
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;

33
kernel/kthread.c
View File

@ -1208,18 +1208,18 @@ void kthread_destroy_worker(struct kthread_worker *worker)
}
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_unuse_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
/**

6
mm/oom_kill.c
View File

@ -126,7 +126,7 @@ static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
/*
* 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 task_struct *victim, const char *message)
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;

4
mm/vmacache.c
View File

@ -24,8 +24,8 @@
* 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)
{