GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-06-28 01:21:58 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

mm: rename _count, field of the struct page, to _refcount

Browse source 
Many developers already know that field for reference count of the
struct page is _count and atomic type.  They would try to handle it
directly and this could break the purpose of page reference count
tracepoint.  To prevent direct _count modification, this patch rename it
to _refcount and add warning message on the code.  After that, developer
who need to handle reference count will find that field should not be
accessed directly.

[akpm@linux-foundation.org: fix comments, per Vlastimil]
[akpm@linux-foundation.org: Documentation/vm/transhuge.txt too]
[sfr@canb.auug.org.au: sync ethernet driver changes]
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sunil Goutham <sgoutham@cavium.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Manish Chopra <manish.chopra@qlogic.com>
Cc: Yuval Mintz <yuval.mintz@qlogic.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Joonsoo Kim 2016-05-19 17:10:49 -07:00 • committed by Linus Torvalds
parent 6d061f9f61
commit 0139aa7b7f
17 changed files with 58 additions and 54 deletions
Download patch file Download diff file Expand all files Collapse all files

10
Documentation/vm/transhuge.txt
View file

@ -394,9 +394,9 @@ hugepage natively. Once finished you can drop the page table lock.
Refcounting on THP is mostly consistent with refcounting on other compound
pages:
- get_page()/put_page() and GUP operate in head page's ->_count.
- get_page()/put_page() and GUP operate in head page's ->_refcount.
- ->_count in tail pages is always zero: get_page_unless_zero() never
- ->_refcount in tail pages is always zero: get_page_unless_zero() never
succeed on tail pages.
- map/unmap of the pages with PTE entry increment/decrement ->_mapcount
@ -426,15 +426,15 @@ requests to split pinned huge page: it expects page count to be equal to
sum of mapcount of all sub-pages plus one (split_huge_page caller must
have reference for head page).
split_huge_page uses migration entries to stabilize page->_count and
split_huge_page uses migration entries to stabilize page->_refcount and
page->_mapcount.
We safe against physical memory scanners too: the only legitimate way
scanner can get reference to a page is get_page_unless_zero().
All tail pages has zero ->_count until atomic_add(). It prevent scanner
All tail pages has zero ->_refcount until atomic_add(). It prevent scanner
from geting reference to tail page up to the point. After the atomic_add()
we don't care about ->_count value. We already known how many references
we don't care about ->_refcount value. We already known how many references
with should uncharge from head page.
For head page get_page_unless_zero() will succeed and we don't mind. It's