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mm/gup.c: update the documentation 

This patch is an attempt to update the documentation.

 - Add/ remove extra * based on type of function static/global.

 - Add description for functions and their input arguments.

[akpm@linux-foundation.org: s@/*@/**@]
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1588013630-4497-1-git-send-email-jrdr.linux@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Souptick Joarder 2020-06-01 21:48:24 -07:00 committed by Linus Torvalds
parent 8d92890bd6
commit adc8cb406e
1 changed files with 39 additions and 18 deletions
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57
mm/gup.c
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@ -1168,7 +1168,7 @@ static bool vma_permits_fault(struct vm_area_struct *vma,
return true;
}
/*
/**
* fixup_user_fault() - manually resolve a user page fault
* @tsk: the task_struct to use for page fault accounting, or
* NULL if faults are not to be recorded.
@ -1839,7 +1839,7 @@ static long __get_user_pages_remote(struct task_struct *tsk,
gup_flags | FOLL_TOUCH | FOLL_REMOTE);
}
/*
/**
* get_user_pages_remote() - pin user pages in memory
* @tsk: the task_struct to use for page fault accounting, or
* NULL if faults are not to be recorded.
@ -1870,13 +1870,13 @@ static long __get_user_pages_remote(struct task_struct *tsk,
*
* Must be called with mmap_sem held for read or write.
*
* get_user_pages walks a process's page tables and takes a reference to
* each struct page that each user address corresponds to at a given
* get_user_pages_remote walks a process's page tables and takes a reference
* to each struct page that each user address corresponds to at a given
* instant. That is, it takes the page that would be accessed if a user
* thread accesses the given user virtual address at that instant.
*
* This does not guarantee that the page exists in the user mappings when
* get_user_pages returns, and there may even be a completely different
* get_user_pages_remote returns, and there may even be a completely different
* page there in some cases (eg. if mmapped pagecache has been invalidated
* and subsequently re faulted). However it does guarantee that the page
* won't be freed completely. And mostly callers simply care that the page
@ -1888,17 +1888,17 @@ static long __get_user_pages_remote(struct task_struct *tsk,
* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
* be called after the page is finished with, and before put_page is called.
*
* get_user_pages is typically used for fewer-copy IO operations, to get a
* handle on the memory by some means other than accesses via the user virtual
* addresses. The pages may be submitted for DMA to devices or accessed via
* their kernel linear mapping (via the kmap APIs). Care should be taken to
* use the correct cache flushing APIs.
* get_user_pages_remote is typically used for fewer-copy IO operations,
* to get a handle on the memory by some means other than accesses
* via the user virtual addresses. The pages may be submitted for
* DMA to devices or accessed via their kernel linear mapping (via the
* kmap APIs). Care should be taken to use the correct cache flushing APIs.
*
* See also get_user_pages_fast, for performance critical applications.
*
* get_user_pages should be phased out in favor of
* get_user_pages_remote should be phased out in favor of
* get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
* should use get_user_pages because it cannot pass
* should use get_user_pages_remote because it cannot pass
* FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
*/
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
@ -1937,7 +1937,17 @@ static long __get_user_pages_remote(struct task_struct *tsk,
}
#endif /* !CONFIG_MMU */
/*
/**
* get_user_pages() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @vmas: array of pointers to vmas corresponding to each page.
* Or NULL if the caller does not require them.
*
* This is the same as get_user_pages_remote(), just with a
* less-flexible calling convention where we assume that the task
* and mm being operated on are the current task's and don't allow
@ -1960,11 +1970,7 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
}
EXPORT_SYMBOL(get_user_pages);
/*
* We can leverage the VM_FAULT_RETRY functionality in the page fault
* paths better by using either get_user_pages_locked() or
* get_user_pages_unlocked().
*
/**
* get_user_pages_locked() is suitable to replace the form:
*
* down_read(&mm->mmap_sem);
@ -1980,6 +1986,21 @@ EXPORT_SYMBOL(get_user_pages);
* get_user_pages_locked(tsk, mm, ..., pages, &locked);
* if (locked)
* up_read(&mm->mmap_sem);
*
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
*
* We can leverage the VM_FAULT_RETRY functionality in the page fault
* paths better by using either get_user_pages_locked() or
* get_user_pages_unlocked().
*
*/
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,