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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
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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
/**