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authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2016-05-19 17:10:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-19 19:12:14 -0700
commit0139aa7b7fa12ceef095d99dc36606a5b10ab83a (patch)
tree94da74f2f79911a11a3c7c34f73ba971dec41a7e /Documentation/vm
parent6d061f9f6136d477932088c24ce155d7dc785746 (diff)
mm: rename _count, field of the struct page, to _refcount
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>
Diffstat (limited to 'Documentation/vm')
-rw-r--r--Documentation/vm/transhuge.txt10
1 files changed, 5 insertions, 5 deletions
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index d9cb65cf5cfd..fb0e1f2a19cc 100644
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -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