On Sat, Apr 16, 2022 at 01:19:17AM +0200, Fabio M. De Francesco wrote: > Include kernel-doc comments to highmem.rst from > include/kernel/highmem.h. > > From now on, the "Using kmap_atomic" section is redundant and obsolete, > therefore 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> Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx> > --- > Documentation/vm/highmem.rst | 41 ++++++------------------------------ > 1 file changed, 6 insertions(+), 35 deletions(-) > > diff --git a/Documentation/vm/highmem.rst b/Documentation/vm/highmem.rst > index 12dcfbee094d..5dcee6233cd5 100644 > --- a/Documentation/vm/highmem.rst > +++ b/Documentation/vm/highmem.rst > @@ -117,41 +117,6 @@ The kernel contains several ways of creating temporary mappings: > synchronization to unmap. > > > -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 > ========================== > > @@ -190,3 +155,9 @@ The general recommendation is that you don't use more than 8GiB on a 32-bit > machine - although more might work for you and your workload, you're pretty > much on your own - don't expect kernel developers to really care much if things > come apart. > + > + > +Functions > +========= > + > +.. kernel-doc:: include/linux/highmem.h > -- > 2.34.1 >
