diff options
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 49 |
1 files changed, 43 insertions, 6 deletions
diff --git a/mm/memory.c b/mm/memory.c index 602f4283122f..207be99390e9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4726,17 +4726,17 @@ EXPORT_SYMBOL_GPL(generic_access_phys); /* * Access another process' address space as given in mm. If non-NULL, use the * given task for page fault accounting. + * This variant assumes that the mmap_lock is already held by the caller, so + * doesn't take the mmap_lock. */ -int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, - unsigned long addr, void *buf, int len, unsigned int gup_flags) +int __access_remote_vm_locked(struct task_struct *tsk, struct mm_struct *mm, + unsigned long addr, void *buf, int len, + unsigned int gup_flags) { struct vm_area_struct *vma; void *old_buf = buf; int write = gup_flags & FOLL_WRITE; - if (mmap_read_lock_killable(mm)) - return 0; - /* ignore errors, just check how much was successfully transferred */ while (len) { int bytes, ret, offset; @@ -4785,9 +4785,46 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, buf += bytes; addr += bytes; } + return buf - old_buf; +} + +/* + * Access another process' address space as given in mm. If non-NULL, use the + * given task for page fault accounting. + */ +int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, + unsigned long addr, void *buf, int len, unsigned int gup_flags) +{ + int ret; + + if (mmap_read_lock_killable(mm)) + return 0; + + ret = __access_remote_vm_locked(tsk, mm, addr, buf, len, gup_flags); mmap_read_unlock(mm); - return buf - old_buf; + return ret; +} + +/** + * access_remote_vm_locked - access another process' address space, without + * taking the mmap_lock. This allows nested calls from callers that already have + * taken the lock. + * + * @mm: the mm_struct of the target address space + * @addr: start address to access + * @buf: source or destination buffer + * @len: number of bytes to transfer + * @gup_flags: flags modifying lookup behaviour + * + * The caller must hold a reference on @mm, as well as hold the mmap_lock + * + * Return: number of bytes copied from source to destination. + */ +int access_remote_vm_locked(struct mm_struct *mm, unsigned long addr, void *buf, + int len, unsigned int gup_flags) +{ + return __access_remote_vm_locked(NULL, mm, addr, buf, len, gup_flags); } /** |