commit 0fa99fdfe1b38da396d0b2d1496a823bcd0ebea0
Author: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Tue Mar 7 13:02:46 2023 -0500
maple_tree: fix mas_skip_node() end slot detection
Patch series "Fix mas_skip_node() for mas_empty_area()", v2.
mas_empty_area() was incorrectly returning an error when there was room.
The issue was tracked down to mas_skip_node() using the incorrect
end-of-slot count. Instead of using the nodes hard limit, the limit of
data should be used.
mas_skip_node() was also setting the min and max to that of the child
node, which was unnecessary. Within these limits being set, there was
also a bug that corrupted the maple state's max if the offset was set to
the maximum node pivot. The bug was without consequence unless there was
a sufficient gap in the next child node which would cause an error to be
returned.
This patch set fixes these errors by removing the limit setting from
mas_skip_node() and uses the mas_data_end() for slot limits, and adds
tests for all failures discovered.
This patch (of 2):
mas_skip_node() is used to move the maple state to the node with a higher
limit. It does this by walking up the tree and increasing the slot count.
Since slot count may not be able to be increased, it may need to walk up
multiple times to find room to walk right to a higher limit node. The
limit of slots that was being used was the node limit and not the last
location of data in the node. This would cause the maple state to be
shifted outside actual data and enter an error state, thus returning
-EBUSY.
The result of the incorrect error state means that mas_awalk() would
return an error instead of finding the allocation space.
The fix is to use mas_data_end() in mas_skip_node() to detect the nodes
data end point and continue walking the tree up until it is safe to move
to a node with a higher limit.
The walk up the tree also sets the maple state limits so remove the buggy
code from mas_skip_node(). Setting the limits had the unfortunate side
effect of triggering another bug if the parent node was full and the there
was no suitable gap in the second last child, but room in the next child.
mas_skip_node() may also be passed a maple state in an error state from
mas_anode_descend() when no allocations are available. Return on such an
error state immediately.
Link: https://lkml.kernel.org/r/20230307180247.2220303-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20230307180247.2220303-2-Liam.Howlett@oracle.com
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Snild Dolkow <snild@sony.com>
Link: https://lore.kernel.org/linux-mm/cb8dc31a-fef2-1d09-f133-e9f7b9f9e77a@sony.com/
Tested-by: Snild Dolkow <snild@sony.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
JIRA: https://issues.redhat.com/browse/RHEL-5595
Signed-off-by: Nico Pache <npache@redhat.com>
commit 44081c77e8a4aac9c5a010ed0d9ccdcf684041e1
Author: Arnd Bergmann <arnd@arndb.de>
Date: Tue Feb 14 11:30:24 2023 +0100
maple_tree: reduce stack usage with gcc-9 and earlier
gcc-10 changed the way inlining works to be less aggressive, but older
versions run into an oversized stack frame warning whenever
CONFIG_KASAN_STACK is enabled, as that forces variables from inlined
callees to be non-overlapping:
lib/maple_tree.c: In function 'mas_wr_bnode':
lib/maple_tree.c:4320:1: error: the frame size of 1424 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
Change the annotations on mas_store_b_node() and mas_commit_b_node()
to explicitly forbid inlining in this configuration, which is
the same behavior that newer versions already have.
Link: https://lkml.kernel.org/r/20230214103030.1051950-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Vernon Yang <vernon2gm@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 17dc622c7b0f94e49bed030726df4db12ecaa6b5
Author: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Fri Jan 20 11:26:07 2023 -0500
maple_tree: fix mas_prev() and mas_find() state handling
When mas_prev() does not find anything, set the state to MAS_NONE.
Handle the MAS_NONE in mas_find() like a MAS_START.
Link: https://lkml.kernel.org/r/20230120162650.984577-7-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: <syzbot+502859d610c661e56545@syzkaller.appspotmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 1202700c3f8cc5f7e4646c3cf05ee6f7c8bc6ccf
Author: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Fri Jan 20 11:26:06 2023 -0500
maple_tree: fix handle of invalidated state in mas_wr_store_setup()
If an invalidated maple state is encountered during write, reset the maple
state to MAS_START. This will result in a re-walk of the tree to the
correct location for the write.
Link: https://lore.kernel.org/all/20230107020126.1627-1-sj@kernel.org/
Link: https://lkml.kernel.org/r/20230120162650.984577-6-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 50e81c82ad947045c7ed26ddc9acb17276b653b6
Author: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Fri Jan 20 11:26:04 2023 -0500
maple_tree: reduce user error potential
When iterating, a user may operate on the tree and cause the maple state
to be altered and left in an unintuitive state. Detect this scenario and
correct it by setting to the limit and invalidating the state.
Link: https://lkml.kernel.org/r/20230120162650.984577-4-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit f942b0f0528d1198b94b8211c84d4f28a654c0ff
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Jan 11 21:53:48 2023 +0800
maple_tree: fix comment of mte_destroy_walk
The parameter name of maple tree is mt, make the comment be mt instead of
mn, and the separator between the parameter name and the description to be
: instead of -.
Link: https://lkml.kernel.org/r/20230111135348.803181-1-vernon2gm@gmail.com
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 541e06b772c1aaffb3b6a245ccface36d7107af2
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Thu Jan 5 16:05:34 2023 +0000
maple_tree: remove GFP_ZERO from kmem_cache_alloc() and kmem_cache_alloc_bulk()
Preallocations are common in the VMA code to avoid allocating under
certain locking conditions. The preallocations must also cover the
worst-case scenario. Removing the GFP_ZERO flag from the
kmem_cache_alloc() (and bulk variant) calls will reduce the amount of time
spent zeroing memory that may not be used. Only zero out the necessary
area to keep track of the allocations in the maple state. Zero the entire
node prior to using it in the tree.
This required internal changes to node counting on allocation, so the test
code is also updated.
This restores some micro-benchmark performance: up to +9% in mmtests mmap1
by my testing +10% to +20% in mmap, mmapaddr, mmapmany tests reported by
Red Hat
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2149636
Link: https://lkml.kernel.org/r/20230105160427.2988454-1-Liam.Howlett@oracle.com
Signed-off-by: Liam Howlett <Liam.Howlett@oracle.com>
Reported-by: Jirka Hladky <jhladky@redhat.com>
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit e11cb683b2ebc6699bc0ca200442f1b80a51553f
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Dec 21 14:00:58 2022 +0800
maple_tree: refine mab_calc_split function
Invert the conditional judgment of the mid_split, to focus the return
statement in the last statement, which is easier to understand and for
better readability.
Link: https://lkml.kernel.org/r/20221221060058.609003-8-vernon2gm@gmail.com
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 46b345848261009477552d654cb2f65000c30e4d
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Dec 21 14:00:57 2022 +0800
maple_tree: refine ma_state init from mas_start()
If mas->node is an MAS_START, there are three cases, and they all assign
different values to mas->node and mas->offset. So there is no need to set
them to a default value before updating.
Update them directly to make them easier to understand and for better
readability.
Link: https://lkml.kernel.org/r/20221221060058.609003-7-vernon2gm@gmail.com
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 84fd3e1ee395649ac45b7317d44c10b33d0dca79
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Dec 21 14:00:55 2022 +0800
maple_tree: use macro MA_ROOT_PARENT instead of number
When you need to compare whether node->parent is parent of the
root node, using macro MA_ROOT_PARENT is easier to understand
and for better readability.
Link: https://lkml.kernel.org/r/20221221060058.609003-5-vernon2gm@gmail.com
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit bd592703b81a95473f6a01fe731beccd0992236e
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Dec 21 14:00:54 2022 +0800
maple_tree: use mt_node_max() instead of direct operations mt_max[]
Use mt_node_max() to get the maximum number of slots for a node,
rather than direct operations mt_max[], makes it better portability.
Link: https://lkml.kernel.org/r/20221221060058.609003-4-vernon2gm@gmail.com
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit d56c593c8e128c42dc81707c07cbd5af41862214
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Dec 21 14:00:53 2022 +0800
maple_tree: remove extra return statement
For functions with a return type of void, it is unnecessary to
add a reurn statement at the end of the function, so drop it.
Link: https://lkml.kernel.org/r/20221221060058.609003-3-vernon2gm@gmail.com
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 831978e37e93bd3e36612917a4b193278950daff
Author: Vernon Yang <vernon2gm@gmail.com>
Date: Wed Dec 21 14:00:52 2022 +0800
maple_tree: remove extra space and blank line
Patch series "Clean up and refinement for maple tree", v2.
This patchset cleans up and refines some maple tree code. A few small
changes make the code easier to understand and for better readability.
This patch (of 7):
These extra space and blank lines are unnecessary, so drop them.
Link: https://lkml.kernel.org/r/20221221060058.609003-1-vernon2gm@gmail.com
Link: https://lkml.kernel.org/r/20221221060058.609003-2-vernon2gm@gmail.com
Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit ab6ef70a8b0d314c2160af70b0de984664d675e0
Author: Wei Yang <richard.weiyang@gmail.com>
Date: Sat Nov 12 23:43:08 2022 +0000
maple_tree: should get pivots boundary by type
We should get pivots boundary by type. Fixes a potential overindexing of
mt_pivots[].
Link: https://lkml.kernel.org/r/20221112234308.23823-1-richard.weiyang@gmail.com
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 7327e8111adb315423035fb5233533016dfd3f2e
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Wed Jan 11 20:02:07 2023 +0000
maple_tree: fix mas_empty_area_rev() lower bound validation
mas_empty_area_rev() was not correctly validating the start of a gap
against the lower limit. This could lead to the range starting lower than
the requested minimum.
Fix the issue by better validating a gap once one is found.
This commit also adds tests to the maple tree test suite for this issue
and tests the mas_empty_area() function for similar bound checking.
Link: https://lkml.kernel.org/r/20230111200136.1851322-1-Liam.Howlett@oracle.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216911
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: <amanieu@gmail.com>
Link: https://lore.kernel.org/linux-mm/0b9f5425-08d4-8013-aa4c-e620c3b10bb2@leemhuis.info/
Tested-by: Holger Hoffsttte <holger@applied-asynchrony.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 0abb964aae3da746ea2fd4301599a6fa26da58db
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Mon Dec 19 16:20:15 2022 +0000
maple_tree: fix mas_spanning_rebalance() on insufficient data
Mike Rapoport contacted me off-list with a regression in running criu.
Periodic tests fail with an RCU stall during execution. Although rare, it
is possible to hit this with other uses so this patch should be backported
to fix the regression.
This patchset adds the fix and a test case to the maple tree test
suite.
This patch (of 2):
An insufficient node was causing an out-of-bounds access on the node in
mas_leaf_max_gap(). The cause was the faulty detection of the new node
being a root node when overwriting many entries at the end of the tree.
Fix the detection of a new root and ensure there is sufficient data prior
to entering the spanning rebalance loop.
Link: https://lkml.kernel.org/r/20221219161922.2708732-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20221219161922.2708732-2-Liam.Howlett@oracle.com
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Mike Rapoport <rppt@kernel.org>
Tested-by: Mike Rapoport <rppt@kernel.org>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 6e7ba8b5e2380f941dda8a1025d70c5ce5b38982
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Fri Oct 28 14:45:34 2022 +0000
maple_tree: mte_set_full() and mte_clear_full() clang-analyzer clean up
mte_set_full() and mte_clear_full() were incorrectly setting a pointer to
a value without returning a result. Fix this by returning the modified
pointer to be use as necessary. Also add a third function to return if
the bit is set or not.
Link: https://lore.kernel.org/lkml/20221026120029.12555-1-lukas.bulwahn@gmail.com/
Link: https://lkml.kernel.org/r/20221028144520.2776767-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 7dc5ba6254bb242a9f45e43549171a2d84d25e6a
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Mon Nov 7 16:39:02 2022 +0000
maple_tree: don't set a new maximum on the node when not reusing nodes
In RCU mode, the node limits were being updated to the last pivot which
may not be correct and would cause the metadata to be set when it
shouldn't. Fix this by not setting a new limit in this case.
Link: https://lkml.kernel.org/r/20221107163857.867377-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 9bbba5633488ee3e2903647c3484c4390ff39ea7
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Mon Nov 7 16:38:35 2022 +0000
maple_tree: fix depth tracking in maple_state
It is possible to confuse the depth tracking in the maple state by
searching the same node for values. Fix the depth tracking by moving
where the depth is incremented closer to where the node changes level.
Also change the initial depth setting when using the root node.
Link: https://lkml.kernel.org/r/20221107163814.866612-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
Conflicts:
lib/Kconfig.debug: was not expecting TEST_XARRAY config
commit 120b116208a0877227fc82e3f0df81e7a3ed4ab1
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Fri Oct 28 18:04:30 2022 +0000
maple_tree: reorganize testing to restore module testing
Along the development cycle, the testing code support for module/in-kernel
compiles was removed. Restore this functionality by moving any internal
API tests to the userspace side, as well as threading tests. Fix the
lockdep issues and add a way to reduce memory usage so the tests can
complete with KASAN + memleak detection. Make the tests work on 32 bit
hosts where possible and detect 32 bit hosts in the radix test suite.
[akpm@linux-foundation.org: fix module export]
[akpm@linux-foundation.org: fix it some more]
[liam.howlett@oracle.com: fix compile warnings on 32bit build in check_find()]
Link: https://lkml.kernel.org/r/20221107203816.1260327-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20221028180415.3074673-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 9a887877ef981e5a185a84339603300cf2eb1900
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Wed Oct 26 15:14:31 2022 +0000
maple_tree: mas_anode_descend() clang-analyzer cleanup
clang-analyzer reported some Dead Stores in mas_anode_descend(). Upon
inspection, there were a few clean ups that would make the code cleaner:
The count variable was set from the mt_slots array and then updated but
never used again. Just use the array reference directly.
Also stop updating the type since it isn't used after the update.
Stop setting the gaps pointer to NULL at the start since it is always
set before the loop begins.
Link: https://lkml.kernel.org/r/20221026151413.4032730-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit c61b3a2b2d9bb36698f8c2f65aa41ba183815264
Author: Liam Howlett <liam.howlett@oracle.com>
Date: Wed Oct 26 15:13:29 2022 +0000
maple_tree: remove pointer to pointer use in mas_alloc_nodes()
There is a more direct and cleaner way of implementing the same functional
code. Remove the confusing and unnecessary use of pointers here.
Link: https://lkml.kernel.org/r/20221026151241.4031117-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
commit 1b9c918318476b4441ddd754ee6699b5367bb5ee
Author: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Date: Wed Oct 26 14:00:29 2022 +0200
lib: maple_tree: remove unneeded initialization in mtree_range_walk()
Before the do-while loop in mtree_range_walk(), the variables next, min,
max need to be initialized. The variables last, prev_min and prev_max are
set within the loop body before they are eventually used after exiting the
loop body.
As it is a do-while loop, the loop body is executed at least once, so the
variables last, prev_min and prev_max do not need to be initialized before
the loop body.
Remove unneeded initialization of last and prev_min.
The needless initialization was reported by clang-analyzer as Dead Stores.
As the compiler already identifies these assignments as unneeded, it
optimizes the assignments away. Hence:
No functional change. No change in object code.
Link: https://lkml.kernel.org/r/20221026120029.12555-2-lukas.bulwahn@gmail.com
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
Conflicts:
lib/Makefile: slight makefile conflict
commit 54a611b605901c7d5d05b6b8f5d04a6ceb0962aa
Author: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Tue Sep 6 19:48:39 2022 +0000
Maple Tree: add new data structure
Patch series "Introducing the Maple Tree"
The maple tree is an RCU-safe range based B-tree designed to use modern
processor cache efficiently. There are a number of places in the kernel
that a non-overlapping range-based tree would be beneficial, especially
one with a simple interface. If you use an rbtree with other data
structures to improve performance or an interval tree to track
non-overlapping ranges, then this is for you.
The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf
nodes. With the increased branching factor, it is significantly shorter
than the rbtree so it has fewer cache misses. The removal of the linked
list between subsequent entries also reduces the cache misses and the need
to pull in the previous and next VMA during many tree alterations.
The first user that is covered in this patch set is the vm_area_struct,
where three data structures are replaced by the maple tree: the augmented
rbtree, the vma cache, and the linked list of VMAs in the mm_struct. The
long term goal is to reduce or remove the mmap_lock contention.
The plan is to get to the point where we use the maple tree in RCU mode.
Readers will not block for writers. A single write operation will be
allowed at a time. A reader re-walks if stale data is encountered. VMAs
would be RCU enabled and this mode would be entered once multiple tasks
are using the mm_struct.
Davidlor said
: Yes I like the maple tree, and at this stage I don't think we can ask for
: more from this series wrt the MM - albeit there seems to still be some
: folks reporting breakage. Fundamentally I see Liam's work to (re)move
: complexity out of the MM (not to say that the actual maple tree is not
: complex) by consolidating the three complimentary data structures very
: much worth it considering performance does not take a hit. This was very
: much a turn off with the range locking approach, which worst case scenario
: incurred in prohibitive overhead. Also as Liam and Matthew have
: mentioned, RCU opens up a lot of nice performance opportunities, and in
: addition academia[1] has shown outstanding scalability of address spaces
: with the foundation of replacing the locked rbtree with RCU aware trees.
A similar work has been discovered in the academic press
https://pdos.csail.mit.edu/papers/rcuvm:asplos12.pdf
Sheer coincidence. We designed our tree with the intention of solving the
hardest problem first. Upon settling on a b-tree variant and a rough
outline, we researched ranged based b-trees and RCU b-trees and did find
that article. So it was nice to find reassurances that we were on the
right path, but our design choice of using ranges made that paper unusable
for us.
This patch (of 70):
The maple tree is an RCU-safe range based B-tree designed to use modern
processor cache efficiently. There are a number of places in the kernel
that a non-overlapping range-based tree would be beneficial, especially
one with a simple interface. If you use an rbtree with other data
structures to improve performance or an interval tree to track
non-overlapping ranges, then this is for you.
The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf
nodes. With the increased branching factor, it is significantly shorter
than the rbtree so it has fewer cache misses. The removal of the linked
list between subsequent entries also reduces the cache misses and the need
to pull in the previous and next VMA during many tree alterations.
The first user that is covered in this patch set is the vm_area_struct,
where three data structures are replaced by the maple tree: the augmented
rbtree, the vma cache, and the linked list of VMAs in the mm_struct. The
long term goal is to reduce or remove the mmap_lock contention.
The plan is to get to the point where we use the maple tree in RCU mode.
Readers will not block for writers. A single write operation will be
allowed at a time. A reader re-walks if stale data is encountered. VMAs
would be RCU enabled and this mode would be entered once multiple tasks
are using the mm_struct.
There is additional BUG_ON() calls added within the tree, most of which
are in debug code. These will be replaced with a WARN_ON() call in the
future. There is also additional BUG_ON() calls within the code which
will also be reduced in number at a later date. These exist to catch
things such as out-of-range accesses which would crash anyways.
Link: https://lkml.kernel.org/r/20220906194824.2110408-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220906194824.2110408-2-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166668
Signed-off-by: Nico Pache <npache@redhat.com>
Nico Pache