linux/fs/f2fs
Jérôme Glisse 2916ecc0f9 mm/migrate: new migrate mode MIGRATE_SYNC_NO_COPY
Introduce a new migration mode that allow to offload the copy to a device
DMA engine.  This changes the workflow of migration and not all
address_space migratepage callback can support this.

This is intended to be use by migrate_vma() which itself is use for thing
like HMM (see include/linux/hmm.h).

No additional per-filesystem migratepage testing is needed.  I disables
MIGRATE_SYNC_NO_COPY in all problematic migratepage() callback and i
added comment in those to explain why (part of this patch).  The commit
message is unclear it should say that any callback that wish to support
this new mode need to be aware of the difference in the migration flow
from other mode.

Some of these callbacks do extra locking while copying (aio, zsmalloc,
balloon, ...) and for DMA to be effective you want to copy multiple
pages in one DMA operations.  But in the problematic case you can not
easily hold the extra lock accross multiple call to this callback.

Usual flow is:

For each page {
 1 - lock page
 2 - call migratepage() callback
 3 - (extra locking in some migratepage() callback)
 4 - migrate page state (freeze refcount, update page cache, buffer
     head, ...)
 5 - copy page
 6 - (unlock any extra lock of migratepage() callback)
 7 - return from migratepage() callback
 8 - unlock page
}

The new mode MIGRATE_SYNC_NO_COPY:
 1 - lock multiple pages
For each page {
 2 - call migratepage() callback
 3 - abort in all problematic migratepage() callback
 4 - migrate page state (freeze refcount, update page cache, buffer
     head, ...)
} // finished all calls to migratepage() callback
 5 - DMA copy multiple pages
 6 - unlock all the pages

To support MIGRATE_SYNC_NO_COPY in the problematic case we would need a
new callback migratepages() (for instance) that deals with multiple
pages in one transaction.

Because the problematic cases are not important for current usage I did
not wanted to complexify this patchset even more for no good reason.

Link: http://lkml.kernel.org/r/20170817000548.32038-14-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Sherry Cheung <SCheung@nvidia.com>
Cc: Subhash Gutti <sgutti@nvidia.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Bob Liu <liubo95@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08 18:26:46 -07:00
..
acl.c f2fs: Don't clear SGID when inheriting ACLs 2017-07-15 21:10:23 -07:00
acl.h f2fs: remove dead code f2fs_check_acl 2016-09-14 16:52:36 -07:00
checkpoint.c f2fs: avoid cpu lockup 2017-07-17 19:23:18 -07:00
data.c mm/migrate: new migrate mode MIGRATE_SYNC_NO_COPY 2017-09-08 18:26:46 -07:00
debug.c f2fs: show available_nids in f2fs/status 2017-05-03 10:04:57 -07:00
dir.c f2fs: do not set LOST_PINO for newly created dir 2017-07-07 10:34:45 -07:00
extent_cache.c f2fs: fix a bug caused by NULL extent tree 2017-05-23 21:07:18 -07:00
f2fs.h for-f2fs-4.13 2017-07-10 14:29:45 -07:00
file.c Writeback error handling fixes for v4.14 2017-09-06 14:11:03 -07:00
gc.c f2fs: introduce io_list for serialize data/node IOs 2017-05-23 21:09:03 -07:00
gc.h f2fs: detect idle time depending on user behavior 2016-01-11 15:56:37 -08:00
hash.c f2fs: check entire encrypted bigname when finding a dentry 2017-05-04 11:44:35 -04:00
inline.c f2fs: use proper variable name 2017-07-04 02:11:40 -07:00
inode.c f2fs: support plain user/group quota 2017-07-08 23:12:27 -07:00
Kconfig f2fs: add mount option to select fault injection ratio 2016-05-07 10:32:22 -07:00
Makefile f2fs: move sysfs code from super.c to fs/f2fs/sysfs.c 2017-07-04 02:11:45 -07:00
namei.c f2fs: support plain user/group quota 2017-07-08 23:12:27 -07:00
node.c for-f2fs-4.13 2017-07-10 14:29:45 -07:00
node.h f2fs: simplify the way of calulating next nat address 2017-07-04 02:11:34 -07:00
recovery.c f2fs: avoid dirty node pages in check_only recovery 2017-04-18 13:37:49 -07:00
segment.c block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
segment.h for-f2fs-4.13 2017-07-10 14:29:45 -07:00
shrinker.c f2fs: avoid casted negative value as shrink count 2016-11-23 12:11:03 -08:00
super.c for-f2fs-4.13 2017-07-10 14:29:45 -07:00
sysfs.c f2fs: include seq_file.h for sysfs.c 2017-07-17 19:23:12 -07:00
trace.c f2fs: use set_page_private marcro in f2fs_trace_pid 2017-03-24 15:10:49 -04:00
trace.h f2fs: add sbi and page pointer in f2fs_io_info 2015-05-28 15:41:32 -07:00
xattr.c f2fs: don't reserve additional space in xattr block 2017-03-24 15:10:53 -04:00
xattr.h f2fs: guard macro variables with braces 2017-04-10 19:48:10 -07:00