commit a4864671ca0bf51c8e78242951741df52c06766f upstream.
It can be used after xas_load to check the order of loaded entries.
Compared to xa_get_order, it saves an XA_STATE and avoid a rewalk.
Added new test for xas_get_order, to make the test work, we have to export
xas_get_order with EXPORT_SYMBOL_GPL.
Also fix a sparse warning by checking the slot value with xa_entry instead
of accessing it directly, as suggested by Matthew Wilcox.
[kasong@tencent.com: simplify comment, sparse warning fix, per Matthew Wilcox]
Link: https://lkml.kernel.org/r/20240416071722.45997-4-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20240415171857.19244-4-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 6758c1128ceb ("mm/filemap: optimize filemap folio adding")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Adds a new line to the docstrings of functions wrapping __xa_alloc() and
__xa_alloc_cyclic(), informing about the necessity of flag XA_FLAGS_ALLOC
being set previously.
The documentation so far says that functions wrapping __xa_alloc() and
__xa_alloc_cyclic() are supposed to return either -ENOMEM or -EBUSY in
case of an error. If the xarray has been initialized without the flag
XA_FLAGS_ALLOC, however, they fail with a different, undocumented error
code.
As hinted at in Documentation/core-api/xarray.rst, wrappers around these
functions should only be invoked when the flag has been set. The
functions' documentation should reflect that as well.
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Shadow_nodes is for shadow nodes reclaiming of workingset handling, it is
updated when page cache add or delete since long time ago workingset only
supported page cache. But when workingset supports anonymous page
detection, we missied updating shadow nodes for it. This caused that
shadow nodes of anonymous page will never be reclaimd by
scan_shadow_nodes() even they use much memory and system memory is tense.
So update shadow_nodes of anonymous page when swap cache is add or delete
by calling xas_set_update(..workingset_update_node).
Link: https://lkml.kernel.org/r/202301182013032211005@zte.com.cn
Fixes: aae466b005 ("mm/swap: implement workingset detection for anonymous LRU")
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Catch bogus GFP flags deterministically, instead of occasionally
when we actually have to allocate memory.
Reported-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
If xas_split_alloc() fails to allocate the necessary nodes to complete the
xarray entry split, it sets the xa_state to -ENOMEM, which xas_nomem()
then interprets as "Please allocate more memory", not as "Please free
any unnecessary memory" (which was the intended outcome). It's confusing
to use xas_nomem() to free memory in this context, so call xas_destroy()
instead.
Reported-by: syzbot+9e27a75a8c24f3fe75c1@syzkaller.appspotmail.com
Fixes: 6b24ca4a1a ("mm: Use multi-index entries in the page cache")
Cc: stable@vger.kernel.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Pull XArray updates from Matthew Wilcox:
- Documentation update
- Fix test-suite build after move of bitmap.h
- Fix xas_create_range() when a large entry is already present
- Fix xas_split() of a shadow entry
* tag 'xarray-5.18' of git://git.infradead.org/users/willy/xarray:
XArray: Update the LRU list in xas_split()
XArray: Fix xas_create_range() when multi-order entry present
XArray: Include bitmap.h from xarray.h
XArray: Document the locking requirement for the xa_state
xas_find_chunk() calls find_next_bit(), which is defined in find.h,
included from bitmap.h. Inside the kernel, this isn't a problem because
bitmap.h is included from cpumask.h which is dragged in (eventually)
by gfp.h. When building the test-suite, that doesn't happen, so we need
to include bitmap.h explicitly.
Fixes: 4ade0818cf ("tools: sync tools/bitmap with mother linux")
Reported-by: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Add a new helper function to help iterate over multi-index entries.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Pull XArray updates from Matthew Wilcox:
- Fix the test suite after introduction of the local_lock
- Fix a bug in the IDA spotted by Coverity
- Change the API that allows the workingset code to delete a node
- Fix xas_reload() when dealing with entries that occupy multiple
indices
- Add a few more tests to the test suite
- Fix an unsigned int being shifted into an unsigned long
* tag 'xarray-5.9' of git://git.infradead.org/users/willy/xarray:
XArray: Fix xas_create_range for ranges above 4 billion
radix-tree: fix the comment of radix_tree_next_slot()
XArray: Fix xas_reload for multi-index entries
XArray: Add private interface for workingset node deletion
XArray: Fix xas_for_each_conflict documentation
XArray: Test marked multiorder iterations
XArray: Test two more things about xa_cmpxchg
ida: Free allocated bitmap in error path
radix tree test suite: Fix compilation
Patch series "Fix read-only THP for non-tmpfs filesystems".
As described more verbosely in the [3/3] changelog, we can inadvertently
put an order-0 page in the page cache which occupies 512 consecutive
entries. Users are running into this if they enable the
READ_ONLY_THP_FOR_FS config option; see
https://bugzilla.kernel.org/show_bug.cgi?id=206569 and Qian Cai has also
reported it here:
https://lore.kernel.org/lkml/20200616013309.GB815@lca.pw/
This is a rather intrusive way of fixing the problem, but has the
advantage that I've actually been testing it with the THP patches, which
means that it sees far more use than it does upstream -- indeed, Song has
been entirely unable to reproduce it. It also has the advantage that it
removes a few patches from my gargantuan backlog of THP patches.
This patch (of 3):
This function returns the order of the entry at the index. We need this
because there isn't space in the shadow entry to encode its order.
[akpm@linux-foundation.org: export xa_get_order to modules]
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Qian Cai <cai@lca.pw>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lkml.kernel.org/r/20200903183029.14930-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20200903183029.14930-2-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
xas_reload() was only checking that the head entry was still at the
head index. If the entry has been split, that's not enough as there
may be a different entry at the specified index now.
Solve this by checking the slot for the requested index instead of the
head index.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Move the tricky bits of dealing with the XArray from the workingset
code to the XArray. Make it clear in the documentation that this is a
private interface, and only export it for the benefit of the test suite.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
At one point, xas_for_each_conflict() was going to work this way,
and I forgot to update the documentation when I changed my mind.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
xas_for_each_marked() is using entry == NULL as a termination condition
of the iteration. When xas_for_each_marked() is used protected only by
RCU, this can however race with xas_store(xas, NULL) in the following
way:
TASK1 TASK2
page_cache_delete() find_get_pages_range_tag()
xas_for_each_marked()
xas_find_marked()
off = xas_find_chunk()
xas_store(&xas, NULL)
xas_init_marks(&xas);
...
rcu_assign_pointer(*slot, NULL);
entry = xa_entry(off);
And thus xas_for_each_marked() terminates prematurely possibly leading
to missed entries in the iteration (translating to missing writeback of
some pages or a similar problem).
If we find a NULL entry that has been marked, skip it (unless we're trying
to allocate an entry).
Reported-by: Jan Kara <jack@suse.cz>
CC: stable@vger.kernel.org
Fixes: ef8e5717db ("page cache: Convert delete_batch to XArray")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
256 means Retry entry and 257 means Zero entry,
so fix it.
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This function supports iterating over a range of an array. Also add
documentation links for xa_for_each_start().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Some users need to take an xarray lock while holding another xarray lock.
Reported-by: Doug Gilbert <dgilbert@interlog.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Since a283348629 ("page cache: Finish XArray conversion"), on most
major Linux distributions, the page cache doesn't correctly transition
when the hot data set is changing, and leaves the new pages thrashing
indefinitely instead of kicking out the cold ones.
On a freshly booted, freshly ssh'd into virtual machine with 1G RAM
running stock Arch Linux:
[root@ham ~]# ./reclaimtest.sh
+ dd of=workingset-a bs=1M count=0 seek=600
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ ./mincore workingset-a
153600/153600 workingset-a
+ dd of=workingset-b bs=1M count=0 seek=600
+ cat workingset-b
+ cat workingset-b
+ cat workingset-b
+ cat workingset-b
+ ./mincore workingset-a workingset-b
104029/153600 workingset-a
120086/153600 workingset-b
+ cat workingset-b
+ cat workingset-b
+ cat workingset-b
+ cat workingset-b
+ ./mincore workingset-a workingset-b
104029/153600 workingset-a
120268/153600 workingset-b
workingset-b is a 600M file on a 1G host that is otherwise entirely
idle. No matter how often it's being accessed, it won't get cached.
While investigating, I noticed that the non-resident information gets
aggressively reclaimed - /proc/vmstat::workingset_nodereclaim. This is
a problem because a workingset transition like this relies on the
non-resident information tracked in the page cache tree of evicted
file ranges: when the cache faults are refaults of recently evicted
cache, we challenge the existing active set, and that allows a new
workingset to establish itself.
Tracing the shrinker that maintains this memory revealed that all page
cache tree nodes were allocated to the root cgroup. This is a problem,
because 1) the shrinker sizes the amount of non-resident information
it keeps to the size of the cgroup's other memory and 2) on most major
Linux distributions, only kernel threads live in the root cgroup and
everything else gets put into services or session groups:
[root@ham ~]# cat /proc/self/cgroup
0::/user.slice/user-0.slice/session-c1.scope
As a result, we basically maintain no non-resident information for the
workloads running on the system, thus breaking the caching algorithm.
Looking through the code, I found the culprit in the above-mentioned
patch: when switching from the radix tree to xarray, it dropped the
__GFP_ACCOUNT flag from the tree node allocations - the flag that
makes sure the allocated memory gets charged to and tracked by the
cgroup of the calling process - in this case, the one doing the fault.
To fix this, allow xarray users to specify per-tree flag that makes
xarray allocate nodes using __GFP_ACCOUNT. Then restore the page cache
tree annotation to request such cgroup tracking for the cache nodes.
With this patch applied, the page cache correctly converges on new
workingsets again after just a few iterations:
[root@ham ~]# ./reclaimtest.sh
+ dd of=workingset-a bs=1M count=0 seek=600
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ cat workingset-a
+ ./mincore workingset-a
153600/153600 workingset-a
+ dd of=workingset-b bs=1M count=0 seek=600
+ cat workingset-b
+ ./mincore workingset-a workingset-b
124607/153600 workingset-a
87876/153600 workingset-b
+ cat workingset-b
+ ./mincore workingset-a workingset-b
81313/153600 workingset-a
133321/153600 workingset-b
+ cat workingset-b
+ ./mincore workingset-a workingset-b
63036/153600 workingset-a
153600/153600 workingset-b
Cc: stable@vger.kernel.org # 4.20+
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Jason feels this is clearer, and it saves a function and an exported
symbol.
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
xa_cmpxchg() was a little too magic in turning ZERO entries into NULL,
and would leave the entry set to the ZERO entry instead of releasing
it for future use. After careful review of existing users of
xa_cmpxchg(), change the semantics so that it does not translate either
incoming argument from NULL into ZERO entries.
Add several tests to the test-suite to make sure this problem doesn't
come back.
Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
