Remove a few hidden (and one visible) calls to compound_head().

Link: https://lkml.kernel.org/r/20220902194653.1739778-12-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Patch series "Folio fixes for 6.0".


This patch (of 2):

The recent folio conversion changed the VM_BUG_ON() to dump the folio
we're storing instead of the entry we retrieved.  This was a mistake;
the entry we retrieved is the more interesting page to dump.

Link: https://lkml.kernel.org/r/20220902192639.1737108-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20220902192639.1737108-2-willy@infradead.org
Fixes: ceff9d33 ("mm/swap: convert __delete_from_swap_cache() to a folio")
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Convert all callers to pass a folio.  Most have the folio
already available.  Switch all users from aops->migratepage to
aops->migrate_folio.  Also turn the documentation into kerneldoc.
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NDavid Sterba <dsterba@suse.com>

All callers now have a folio, so convert the entire function to operate
on folios.

Link: https://lkml.kernel.org/r/20220617175020.717127-23-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

All but one caller already has a folio, so convert it to use a folio.

Link: https://lkml.kernel.org/r/20220617175020.717127-22-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

swap_cache_info are not statistics that could be easily used to tune
system performance because they are not easily accessile.  Also they can't
provide really useful info when OOM occurs.  Remove these statistics can
also help mitigate unneeded global swap_cache_info cacheline contention.

Link: https://lkml.kernel.org/r/20220608144031.829-4-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Suggested-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>
Acked-by: N"Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

These functions have no more users, so delete them.
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: NMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>

There might be swapin error entries in shmem mapping.  Filter them out to
avoid "Bad swap file entry" complaint.

Link: https://lkml.kernel.org/r/20220519125030.21486-6-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NNaoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Use helper macro __ATTR_RW to define vma_ra_enabled_attr to make code more
clear.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220509131416.17553-3-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Patch series "A few cleanup patches for swap".

This series contains a few patches to fix the comment, remove unneeded
return value, use some helpers and so on.  More details can be found in
the respective changelogs.


This patch (of 14):

Use helper is_swap_pte() to check whether pte is swap entry to make code
more clear.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220509131416.17553-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220509131416.17553-2-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

The only caller already has a folio available, so this saves a conversion.
Also convert the return type to boolean.

Link: https://lkml.kernel.org/r/20220504182857.4013401-9-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

This removes an assumption that a large folio is HPAGE_PMD_NR pages
in size.

Link: https://lkml.kernel.org/r/20220504182857.4013401-8-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Sysfs input conversion to corrosponding bool value e.g.  "false" or "0" to
false, "true" or "1" to true are currently handled through strncmp at
multiple places.  Use kstrtobool() to convert sysfs input to bool value.

[akpm@linux-foundation.org: propagate kstrtobool() return value, per Andy]
Link: https://lkml.kernel.org/r/20220426180203.70782-2-jvgediya@linux.ibm.comSigned-off-by: NJagdish Gediya <jvgediya@linux.ibm.com>
Reviewed-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Richard Fitzgerald <rf@opensource.cirrus.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

swap_readpage() is given one page at a time, but may be called repeatedly
in succession.

For block-device swap-space, the blk_plug functionality allows the
multiple pages to be combined together at lower layers.  That cannot be
used for SWP_FS_OPS as blk_plug may not exist - it is only active when
CONFIG_BLOCK=y.  Consequently all swap reads over NFS are single page
reads.

With this patch we pass in a pointer-to-pointer when swap_readpage can
store state between calls - much like the effect of blk_plug.  After
calling swap_readpage() some number of times, the state will be passed to
swap_read_unplug() which can submit the combined request.

Link: https://lkml.kernel.org/r/164859778127.29473.14059420492644907783.stgit@noble.brownSigned-off-by: NNeilBrown <neilb@suse.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NDavid Howells <dhowells@redhat.com>
Tested-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

folios that are written to swap are owned by the MM subsystem - not any
filesystem.

When such a folio is passed to a filesystem to be written out to a
swap-file, the filesystem handles the data, but the folio itself does not
belong to the filesystem.  So calling the filesystem's ->dirty_folio()
address_space operation makes no sense.  This is for folios in the given
address space, and a folio to be written to swap does not exist in the
given address space.

So drop swap_dirty_folio() which calls the address-space's
->dirty_folio(), and always use noop_dirty_folio(), which is appropriate
for folios being swapped out.

Link: https://lkml.kernel.org/r/164859778123.29473.6900942583784889976.stgit@noble.brownSigned-off-by: NNeilBrown <neilb@suse.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NDavid Howells <dhowells@redhat.com>
Tested-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Patch series "MM changes to improve swap-over-NFS support".

Assorted improvements for swap-via-filesystem.

This is a resend of these patches, rebased on current HEAD.  The only
substantial changes is that swap_dirty_folio has replaced
swap_set_page_dirty.

Currently swap-via-fs (SWP_FS_OPS) doesn't work for any filesystem.  It
has previously worked for NFS but that broke a few releases back.  This
series changes to use a new ->swap_rw rather than ->readpage and
->direct_IO.  It also makes other improvements.

There is a companion series already in linux-next which fixes various
issues with NFS.  Once both series land, a final patch is needed which
changes NFS over to use ->swap_rw.


This patch (of 10):

Many functions declared in include/linux/swap.h are only used within mm/

Create a new "mm/swap.h" and move some of these declarations there.
Remove the redundant 'extern' from the function declarations.

[akpm@linux-foundation.org: mm/memory-failure.c needs mm/swap.h]
Link: https://lkml.kernel.org/r/164859751830.29473.5309689752169286816.stgit@noble.brown
Link: https://lkml.kernel.org/r/164859778120.29473.11725907882296224053.stgit@noble.brownSigned-off-by: NNeilBrown <neilb@suse.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NDavid Howells <dhowells@redhat.com>
Tested-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

In our testing, a livelock task was found.  Through sysrq printing, same
stack was found every time, as follows:

  __swap_duplicate+0x58/0x1a0
  swapcache_prepare+0x24/0x30
  __read_swap_cache_async+0xac/0x220
  read_swap_cache_async+0x58/0xa0
  swapin_readahead+0x24c/0x628
  do_swap_page+0x374/0x8a0
  __handle_mm_fault+0x598/0xd60
  handle_mm_fault+0x114/0x200
  do_page_fault+0x148/0x4d0
  do_translation_fault+0xb0/0xd4
  do_mem_abort+0x50/0xb0

The reason for the livelock is that swapcache_prepare() always returns
EEXIST, indicating that SWAP_HAS_CACHE has not been cleared, so that it
cannot jump out of the loop.  We suspect that the task that clears the
SWAP_HAS_CACHE flag never gets a chance to run.  We try to lower the
priority of the task stuck in a livelock so that the task that clears
the SWAP_HAS_CACHE flag will run.  The results show that the system
returns to normal after the priority is lowered.

In our testing, multiple real-time tasks are bound to the same core, and
the task in the livelock is the highest priority task of the core, so
the livelocked task cannot be preempted.

Although cond_resched() is used by __read_swap_cache_async, it is an
empty function in the preemptive system and cannot achieve the purpose
of releasing the CPU.  A high-priority task cannot release the CPU
unless preempted by a higher-priority task.  But when this task is
already the highest priority task on this core, other tasks will not be
able to be scheduled.  So we think we should replace cond_resched() with
schedule_timeout_uninterruptible(1), schedule_timeout_interruptible will
call set_current_state first to set the task state, so the task will be
removed from the running queue, so as to achieve the purpose of giving
up the CPU and prevent it from running in kernel mode for too long.

(akpm: ugly hack becomes uglier.  But it fixes the issue in a
backportable-to-stable fashion while we hopefully work on something
better)

Link: https://lkml.kernel.org/r/20220221111749.1928222-1-cgel.zte@gmail.comSigned-off-by: NGuo Ziliang <guo.ziliang@zte.com.cn>
Reported-by: NZeal Robot <zealci@zte.com.cn>
Reviewed-by: NRan Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: NJiang Xuexin <jiang.xuexin@zte.com.cn>
Reviewed-by: NYang Yang <yang.yang29@zte.com.cn>
Acked-by: NHugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roger Quadros <rogerq@kernel.org>
Cc: Ziliang Guo <guo.ziliang@zte.com.cn>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Straightforward conversion.
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: NDamien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: NDamien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs

This nets us 178 bytes of savings from removing calls to compound_head.
The three callers all grow a little, but each of them will be converted
to use folios soon, so that's fine.
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>

Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b5 ("mm: swap: check if swap backing
device is congested or not") doesn't stand anymore, so the commit could
be just reverted in order to solve the race reported by commit
2efa33fc ("mm/shmem: fix shmem_swapin() race with swapoff").  The
fix was reverted by the previous patch.

Link: https://lkml.kernel.org/r/20210810202936.2672-3-shy828301@gmail.comSigned-off-by: NYang Shi <shy828301@gmail.com>
Suggested-by: NHugh Dickins <hughd@google.com>
Acked-by: NHugh Dickins <hughd@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

To check whether all pages and shadow entries in swap cache has been
removed before swap cache is freed.

Link: https://lkml.kernel.org/r/20210608005121.511140-1-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With commit 09854ba9 ("mm: do_wp_page() simplification"), after COW,
the idle swap cache page (neither the page nor the corresponding swap
entry is mapped by any process) will be left in the LRU list, even if it's
in the active list or the head of the inactive list.  So, the page
reclaimer may take quite some overhead to reclaim these actually unused
pages.

To help the page reclaiming, in this patch, after COW, the idle swap cache
page will be tried to be freed.  To avoid to introduce much overhead to
the hot COW code path,

a) there's almost zero overhead for non-swap case via checking
   PageSwapCache() firstly.

b) the page lock is acquired via trylock only.

To test the patch, we used pmbench memory accessing benchmark with
working-set larger than available memory on a 2-socket Intel server with a
NVMe SSD as swap device.  Test results shows that the pmbench score
increases up to 23.8% with the decreased size of swap cache and swapin
throughput.

Link: https://lkml.kernel.org/r/20210601053143.1380078-1-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>	[use free_swap_cache()]
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@surriel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since commit 55c653b71e8c ("mm: stop accounting shadow entries"),
nr_shadows is not used anymore.

Link: https://lkml.kernel.org/r/20210520134022.1370406-3-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The non_swap_entry() was used for working with VMA based swap readahead
via commit ec560175 ("mm, swap: VMA based swap readahead").  At that
time, the non_swap_entry() checking is necessary because the function is
called before checking that in do_swap_page().  Then it's moved to
swap_ra_info() since commit eaf649eb ("mm: swap: clean up swap
readahead").  After that, the non_swap_entry() checking is unnecessary,
because swap_ra_info() is called after non_swap_entry() has been checked
already.  The resulting code is confusing as the non_swap_entry() check
looks racy now because while we released the pte lock, somebody else might
have faulted in this pte.  So we should check whether it's swap pte first
to guard against such race or swap_type will be unexpected.  But the race
isn't important because it will not cause problem.  We would have enough
checking when we really operate the PTE entries later.  So we remove the
non_swap_entry() check here to avoid confusion.

Link: https://lkml.kernel.org/r/20210426123316.806267-4-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: N"Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fix some typos and code style problems in mm.

gfp.h: s/MAXNODES/MAX_NUMNODES
mmzone.h: s/then/than
rmap.c: s/__vma_split()/__vma_adjust()
swap.c: s/__mod_zone_page_stat/__mod_zone_page_state, s/is is/is
swap_state.c: s/whoes/whose
z3fold.c: code style problem fix in z3fold_unregister_migration
zsmalloc.c: s/of/or, s/give/given

Link: https://lkml.kernel.org/r/20210419083057.64820-1-luoshijie1@huawei.comSigned-off-by: NShijie Luo <luoshijie1@huawei.com>
Signed-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We no longer need to keep track of how many shadow entries are present in
a mapping.  This saves a few writes to the inode and memory barriers.

Link: https://lkml.kernel.org/r/20201026151849.24232-3-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: NVishal Verma <vishal.l.verma@intel.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently the kernel adds the page, allocated for swapin, to the
swapcache before charging the page.  This is fine but now we want a
per-memcg swapcache stat which is essential for folks who wants to
transparently migrate from cgroup v1's memsw to cgroup v2's memory and
swap counters.  In addition charging a page before exposing it to other
parts of the kernel is a step in the right direction.

To correctly maintain the per-memcg swapcache stat, this patch has
adopted to charge the page before adding it to swapcache.  One challenge
in this option is the failure case of add_to_swap_cache() on which we
need to undo the mem_cgroup_charge().  Specifically undoing
mem_cgroup_uncharge_swap() is not simple.

To resolve the issue, this patch decouples the charging for swapin pages
from mem_cgroup_charge().  Two new functions are introduced,
mem_cgroup_swapin_charge_page() for just charging the swapin page and
mem_cgroup_swapin_uncharge_swap() for uncharging the swap slot once the
page has been successfully added to the swapcache.

[shakeelb@google.com: set page->private before calling swap_readpage]
  Link: https://lkml.kernel.org/r/20210318015959.2986837-1-shakeelb@google.com

Link: https://lkml.kernel.org/r/20210305212639.775498-1-shakeelb@google.comSigned-off-by: NShakeel Butt <shakeelb@google.com>
Acked-by: NRoman Gushchin <guro@fb.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NHugh Dickins <hughd@google.com>
Tested-by: NHeiko Carstens <hca@linux.ibm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The functionality of find_lock_entry() and find_get_entry() can be
provided by pagecache_get_page(), which lets us delete find_lock_entry()
and make find_get_entry() static.

Link: https://lkml.kernel.org/r/20201112212641.27837-5-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There's no need to get a reference to the page, just load the entry and
see if it's a shadow entry.

Link: https://lkml.kernel.org/r/20201112212641.27837-4-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch adds swapcache stat for the cgroup v2.  The swapcache
represents the memory that is accounted against both the memory and the
swap limit of the cgroup.  The main motivation behind exposing the
swapcache stat is for enabling users to gracefully migrate from cgroup
v1's memsw counter to cgroup v2's memory and swap counters.

Cgroup v1's memsw limit allows users to limit the memory+swap usage of a
workload but without control on the exact proportion of memory and swap.
Cgroup v2 provides separate limits for memory and swap which enables more
control on the exact usage of memory and swap individually for the
workload.

With some little subtleties, the v1's memsw limit can be switched with the
sum of the v2's memory and swap limits.  However the alternative for memsw
usage is not yet available in cgroup v2.  Exposing per-cgroup swapcache
stat enables that alternative.  Adding the memory usage and swap usage and
subtracting the swapcache will approximate the memsw usage.  This will
help in the transparent migration of the workloads depending on memsw
usage and limit to v2' memory and swap counters.

The reasons these applications are still interested in this approximate
memsw usage are: (1) these applications are not really interested in two
separate memory and swap usage metrics.  A single usage metric is more
simple to use and reason about for them.

(2) The memsw usage metric hides the underlying system's swap setup from
the applications.  Applications with multiple instances running in a
datacenter with heterogeneous systems (some have swap and some don't) will
keep seeing a consistent view of their usage.

[akpm@linux-foundation.org: fix CONFIG_SWAP=n build]

Link: https://lkml.kernel.org/r/20210108155813.2914586-3-shakeelb@google.comSigned-off-by: NShakeel Butt <shakeelb@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NRoman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are capable of SetPageWorkingset based on refault distances after
commit aae466b0 ("mm/swap: implement workingset detection for
anonymous LRU").  This is done by workingset_refault(), which is right
above the unconditional SetPageWorkingset deleted by this patch.

The unconditional SetPageWorkingset miscategorizes pages that are read
ahead or never belonged to the working set (e.g., tmpfs pages accessed
only once by fd).  When those pages are swapped in (after they were
swapped out) for the first time, they skew PSI (when using async swap).
When this happens again, depending on their refault distances, they might
skew workingset_restore_anon counter in addition to PSI because their
shadows indicate they were part of the working set.

Historically, SetPageWorkingset was added as part of the PSI series, and
Johannes said:
 "It was meant to mark incoming pages under IO with SetPageWorkingset
  when waiting for them constituted a memory stall.

  On the page cache side, because we HAVE workingset detection, this was
  specific to recently evicted pages that had been active in their
  previous life. On the anon side, the aging algorithm had no
  distinction between workingset and sporadically used pages. Given the
  choice between a) no swapin stalls are pressure and b) all swapin
  stalls are pressure, I went with the latter in order to detect swap
  storms. The false positive case - high rate of swapin without severe
  memory pressure - was relatively unlikely, because we tried to avoid
  swapping until everything was completely on fire in the first place."

Link: https://lkml.kernel.org/r/20201209012400.1771150-1-yuzhao@google.com
Link: https://lkml.kernel.org/r/20201214231253.62313-1-yuzhao@google.comSigned-off-by: NYu Zhao <yuzhao@google.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The only usage of swap_attr_group is to pass its address to
sysfs_create_group() which takes a pointer to const attribute_group.  Make
it const to allow the compiler to put it in read-only memory.

Link: https://lkml.kernel.org/r/20210201233254.91809-1-rikard.falkeborn@gmail.comSigned-off-by: NRikard Falkeborn <rikard.falkeborn@gmail.com>
Reviewed-by: NAmy Parker <enbyamy@gmail.com>
Acked-by: N"Huang, Ying" <ying.huang@intel.com>
Reviewed-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "mm: Convert sysfs sprintf family to sysfs_emit", v2.

Use the new sysfs_emit family and not the sprintf family.

This patch (of 5):

Use the sysfs_emit function instead of the sprintf family.

Done with cocci script as in commit 3c6bff3c ("RDMA: Convert sysfs
kobject * show functions to use sysfs_emit()")

Link: https://lkml.kernel.org/r/cover.1605376435.git.joe@perches.com
Link: https://lkml.kernel.org/r/9c249215bad6df616ba0410ad980042694970c1b.1605376435.git.joe@perches.comSigned-off-by: NJoe Perches <joe@perches.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

swap_ra_info() may leave ra_info untouched in non_swap_entry() case as
page table lock is not held.  In this case, we have ra_info.nr_pte == 0
and it is meaningless to continue with swap cache readahead.  Skip such
ops by init ra_info.win = 1.

[akpm@linux-foundation.org: clean up struct init]

Link: https://lkml.kernel.org/r/20201009133059.58407-1-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix some broken comments including typo, grammar error and wrong function
name.
Signed-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200913095456.54873-1-linmiaohe@huawei.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

SWP_FS is used to make swap_{read,write}page() go through the filesystem,
and it's only used for swap files over NFS for now.  Otherwise it will
directly submit IO to blockdev according to swapfile extents reported by
filesystems in advance.

As Matthew pointed out [1], SWP_FS naming is somewhat confusing, so let's
rename to SWP_FS_OPS.

[1] https://lore.kernel.org/r/20200820113448.GM17456@casper.infradead.orgSuggested-by: NMatthew Wilcox <willy@infradead.org>
Signed-off-by: NGao Xiang <hsiangkao@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200822113019.11319-1-hsiangkao@redhat.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are only four callers remaining of find_get_entry().
get_shadow_from_swap_cache() only wants to see shadow entries and doesn't
care about which page is returned.  Push the find_subpage() call into
find_lock_entry(), find_get_incore_page() and pagecache_get_page().

[willy@infradead.org: fix oops]
  Link: https://lkml.kernel.org/r/20200914112738.GM6583@casper.infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Link: https://lkml.kernel.org/r/20200910183318.20139-7-willy@infradead.orgSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "Return head pages from find_*_entry", v2.

This patch series started out as part of the THP patch set, but it has
some nice effects along the way and it seems worth splitting it out and
submitting separately.

Currently find_get_entry() and find_lock_entry() return the page
corresponding to the requested index, but the first thing most callers do
is find the head page, which we just threw away.  As part of auditing all
the callers, I found some misuses of the APIs and some plain
inefficiencies that I've fixed.

The diffstat is unflattering, but I added more kernel-doc and a new wrapper.

This patch (of 8);

Provide this functionality from the swap cache.  It's useful for
more than just mincore().
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Link: https://lkml.kernel.org/r/20200910183318.20139-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20200910183318.20139-2-willy@infradead.orgSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

swap_cache_info.* could be accessed concurrently as noticed by
KCSAN,

 BUG: KCSAN: data-race in lookup_swap_cache / lookup_swap_cache

 write to 0xffffffff85517318 of 8 bytes by task 94138 on cpu 101:
  lookup_swap_cache+0x12e/0x460
  lookup_swap_cache at mm/swap_state.c:322
  do_swap_page+0x112/0xeb0
  __handle_mm_fault+0xc7a/0xd00
  handle_mm_fault+0xfc/0x2f0
  do_page_fault+0x263/0x6f9
  page_fault+0x34/0x40

 read to 0xffffffff85517318 of 8 bytes by task 91655 on cpu 100:
  lookup_swap_cache+0x117/0x460
  lookup_swap_cache at mm/swap_state.c:322
  shmem_swapin_page+0xc7/0x9e0
  shmem_getpage_gfp+0x2ca/0x16c0
  shmem_fault+0xef/0x3c0
  __do_fault+0x9e/0x220
  do_fault+0x4a0/0x920
  __handle_mm_fault+0xc69/0xd00
  handle_mm_fault+0xfc/0x2f0
  do_page_fault+0x263/0x6f9
  page_fault+0x34/0x40

 Reported by Kernel Concurrency Sanitizer on:
 CPU: 100 PID: 91655 Comm: systemd-journal Tainted: G        W  O L 5.5.0-next-20200204+ #6
 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019

 write to 0xffffffff8d717308 of 8 bytes by task 11365 on cpu 87:
   __delete_from_swap_cache+0x681/0x8b0
   __delete_from_swap_cache at mm/swap_state.c:178

 read to 0xffffffff8d717308 of 8 bytes by task 11275 on cpu 53:
   __delete_from_swap_cache+0x66e/0x8b0
   __delete_from_swap_cache at mm/swap_state.c:178

Both the read and write are done as lockless. Since swap_cache_info.*
are only used to print out counter information, even if any of them
missed a few incremental due to data races, it will be harmless, so just
mark it as an intentional data race using the data_race() macro.

While at it, fix a checkpatch.pl warning,

WARNING: Single statement macros should not use a do {} while (0) loop
Signed-off-by: NQian Cai <cai@lca.pw>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Link: http://lkml.kernel.org/r/20200207003715.1578-1-cai@lca.pwSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The thp prefix is more frequently used than hpage and we should be
consistent between the various functions.

[akpm@linux-foundation.org: fix mm/migrate.c]
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: NZi Yan <ziy@nvidia.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20200629151959.15779-6-willy@infradead.orgSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>