tag | 02ab7a3b7c128faac6158bdc4a424abdbb06f6fe | |
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tagger | Howard Chen <howardsoc@google.com> | Tue Nov 14 09:48:37 2023 +0800 |
object | c8a4222899da9a7daeb3efa374b2cd5493fbd905 |
android14-6.1 July 2023 release 11 Artifacts: https://ci.android.com/builds/submitted/11084377/kernel_aarch64/latest
commit | c8a4222899da9a7daeb3efa374b2cd5493fbd905 | [log] [tgz] |
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author | Suren Baghdasaryan <surenb@google.com> | Sat Jul 08 12:12:12 2023 -0700 |
committer | Will Deacon <willdeacon@google.com> | Fri Nov 10 11:15:59 2023 +0000 |
tree | 61c6c8387cf3df36ed2b77cd6ca08940879153fe | |
parent | 6864d7f28cd6a3da50ee3640ecb3c0fba67a6896 [diff] |
UPSTREAM: fork: lock VMAs of the parent process when forking When forking a child process, the parent write-protects anonymous pages and COW-shares them with the child being forked using copy_present_pte(). We must not take any concurrent page faults on the source vma's as they are being processed, as we expect both the vma and the pte's behind it to be stable. For example, the anon_vma_fork() expects the parents vma->anon_vma to not change during the vma copy. A concurrent page fault on a page newly marked read-only by the page copy might trigger wp_page_copy() and a anon_vma_prepare(vma) on the source vma, defeating the anon_vma_clone() that wasn't done because the parent vma originally didn't have an anon_vma, but we now might end up copying a pte entry for a page that has one. Before the per-vma lock based changes, the mmap_lock guaranteed exclusion with concurrent page faults. But now we need to do a vma_start_write() to make sure no concurrent faults happen on this vma while it is being processed. This fix can potentially regress some fork-heavy workloads. Kernel build time did not show noticeable regression on a 56-core machine while a stress test mapping 10000 VMAs and forking 5000 times in a tight loop shows ~5% regression. If such fork time regression is unacceptable, disabling CONFIG_PER_VMA_LOCK should restore its performance. Further optimizations are possible if this regression proves to be problematic. Bug: 310069501 Suggested-by: David Hildenbrand <david@redhat.com> Reported-by: Jiri Slaby <jirislaby@kernel.org> Closes: https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51b@kernel.org/ Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com> Closes: https://lore.kernel.org/all/b198d649-f4bf-b971-31d0-e8433ec2a34c@applied-asynchrony.com/ Reported-by: Jacob Young <jacobly.alt@gmail.com> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217624 Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling first") Cc: stable@vger.kernel.org Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> (cherry picked from commit fb49c455323ff8319a123dd312be9082c49a23a5) Change-Id: Ic5aa9dc51a888b5b0319ec4ec6d2941424573ca0 Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@google.com> (cherry picked from commit 0d9960403cb0fa936ab8dc34462ec446f3699c2e)
BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.
EXPORT_SYMBOL_GPL()
require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.
scripts/checkpatch.pl
UPSTREAM:
, BACKPORT:
, FROMGIT:
, FROMLIST:
, or ANDROID:
.Change-Id:
tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)Bug:
tag.Signed-off-by:
tag by the author and the submitterAdditional requirements are listed below based on patch type
UPSTREAM:
, BACKPORT:
UPSTREAM:
.(cherry picked from commit ...)
lineimportant patch from upstream This is the detailed description of the important patch Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
UPSTREAM: important patch from upstream This is the detailed description of the important patch Signed-off-by: Fred Jones <fred.jones@foo.org> Bug: 135791357 Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01 (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1) Signed-off-by: Joe Smith <joe.smith@foo.org>
BACKPORT:
instead of UPSTREAM:
.UPSTREAM:
(cherry picked from commit ...)
lineBACKPORT: important patch from upstream This is the detailed description of the important patch Signed-off-by: Fred Jones <fred.jones@foo.org> Bug: 135791357 Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01 (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1) [joe: Resolved minor conflict in drivers/foo/bar.c ] Signed-off-by: Joe Smith <joe.smith@foo.org>
FROMGIT:
, FROMLIST:
,FROMGIT:
(cherry picked from commit <sha1> <repo> <branch>)
. This must be a stable maintainer branch (not rebased, so don't use linux-next
for example).BACKPORT: FROMGIT:
important patch from upstream This is the detailed description of the important patch Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
FROMGIT: important patch from upstream This is the detailed description of the important patch Signed-off-by: Fred Jones <fred.jones@foo.org> Bug: 135791357 (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch) Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01 Signed-off-by: Joe Smith <joe.smith@foo.org>
FROMLIST:
Link:
tag with a link to the submittal on lore.kernel.orgBug:
tag with the Android bug (required for patches not accepted into a maintainer tree)BACKPORT: FROMLIST:
FROMLIST: important patch from upstream This is the detailed description of the important patch Signed-off-by: Fred Jones <fred.jones@foo.org> Bug: 135791357 Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/ Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01 Signed-off-by: Joe Smith <joe.smith@foo.org>
ANDROID:
ANDROID:
Fixes:
tag that cites the patch with the bugANDROID: fix android-specific bug in foobar.c This is the detailed description of the important fix Fixes: 1234abcd2468 ("foobar: add cool feature") Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01 Signed-off-by: Joe Smith <joe.smith@foo.org>
ANDROID:
Bug:
tag with the Android bug (required for android-specific features)