linux/Documentation/vm
Pavel Emelyanov 541c237c09 pagemap: prepare to reuse constant bits with page-shift
In order to reuse bits from pagemap entries gracefully, we leave the
entries as is but on pagemap open emit a warning in dmesg, that bits
55-60 are about to change in a couple of releases.  Next, if a user
issues soft-dirty clear command via the clear_refs file (it was disabled
before v3.9) we assume that he's aware of the new pagemap format, note
that fact and report the bits in pagemap in the new manner.

The "migration strategy" looks like this then:

1. existing users are not affected -- they don't touch soft-dirty feature, thus
   see old bits in pagemap, but are warned and have time to fix themselves
2. those who use soft-dirty know about new pagemap format
3. some time soon we get rid of any signs of page-shift in pagemap as well as
   this trick with clear-soft-dirty affecting pagemap format.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-03 16:07:26 -07:00
..
.gitignore
00-INDEX
active_mm.txt
balance
cleancache.txt
frontswap.txt
highmem.txt
hugetlbpage.txt
hwpoison.txt
ksm.txt ksm: add some comments 2013-02-23 17:50:23 -08:00
locking
numa
numa_memory_policy.txt
overcommit-accounting mm: limit growth of 3% hardcoded other user reserve 2013-04-29 15:54:36 -07:00
page_migration
pagemap.txt pagemap: prepare to reuse constant bits with page-shift 2013-07-03 16:07:26 -07:00
slub.txt
soft-dirty.txt mm: soft-dirty bits for user memory changes tracking 2013-07-03 16:07:26 -07:00
transhuge.txt thp: introduce sysfs knob to disable huge zero page 2012-12-12 17:38:32 -08:00
unevictable-lru.txt