The use of kmap_atomic() is deprecated in favor of kmap_local_page(). For this reason the "Using kmap_atomic" section in highmem.rst is obsolete and unnecessary. Therefore, just remove it. Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ira Weiny <ira.weiny@xxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> --- Documentation/vm/highmem.rst | 35 ----------------------------------- 1 file changed, 35 deletions(-) diff --git a/Documentation/vm/highmem.rst b/Documentation/vm/highmem.rst index ccff08a8211d..e05bf5524174 100644 --- a/Documentation/vm/highmem.rst +++ b/Documentation/vm/highmem.rst @@ -72,41 +72,6 @@ The kernel contains several ways of creating temporary mappings: It may be assumed that k[un]map_atomic() won't fail. -Using kmap_atomic -================= - -When and where to use kmap_atomic() is straightforward. It is used when code -wants to access the contents of a page that might be allocated from high memory -(see __GFP_HIGHMEM), for example a page in the pagecache. The API has two -functions, and they can be used in a manner similar to the following:: - - /* Find the page of interest. */ - struct page *page = find_get_page(mapping, offset); - - /* Gain access to the contents of that page. */ - void *vaddr = kmap_atomic(page); - - /* Do something to the contents of that page. */ - memset(vaddr, 0, PAGE_SIZE); - - /* Unmap that page. */ - kunmap_atomic(vaddr); - -Note that the kunmap_atomic() call takes the result of the kmap_atomic() call -not the argument. - -If you need to map two pages because you want to copy from one page to -another you need to keep the kmap_atomic calls strictly nested, like:: - - vaddr1 = kmap_atomic(page1); - vaddr2 = kmap_atomic(page2); - - memcpy(vaddr1, vaddr2, PAGE_SIZE); - - kunmap_atomic(vaddr2); - kunmap_atomic(vaddr1); - - Cost of Temporary Mappings ========================== -- 2.34.1
