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| author | Lokesh Gidra <lokeshgidra@google.com> | 2024-03-08 10:59:56 -0800 |
|---|---|---|
| committer | Jhih-Chen Huang <jhihchen@google.com> | 2024-03-27 08:38:58 +0000 |
| commit | b26824bed88d7ef26dcfc12d6ccc9a5176df6fa1 (patch) | |
| tree | 8172b241082c95c249e58ebfa69e369612c4bf08 | |
| parent | a439a1a38751f18efe2639142b03864df13bc5e3 (diff) | |
| download | common-b26824bed88d7ef26dcfc12d6ccc9a5176df6fa1.tar.gz | |
ANDROID: userfaultfd: abort uffdio ops if mmap_lock is contendedandroid13-5.10-2024-03_r2
Check if the mmap_lock is contended when looping over the pages that
are requested to be filled. When it is observed, we rely on the already
existing mechanism to return bytes copied/filled and -EAGAIN as error.
This helps by avoiding contention of mmap_lock for long running
userfaultfd operations. The userspace can perform other tasks before
retrying the operation for the remaining pages.
Bug: 320478828
Bug: 331535903
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:6bc28fdfeec3373198d11fae1c9663a598ddb05c)
Merged-In: I6d485fd03c96a826956ee3962e58058be3cf81c1
Change-Id: I6d485fd03c96a826956ee3962e58058be3cf81c1
| -rw-r--r-- | mm/userfaultfd.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 7e7fee431873..e8e8a7951c4a 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -664,6 +664,15 @@ retry: if (unlikely(err == -ENOENT)) { void *page_kaddr; + /* + * Return early due to mmap_lock contention only after + * some pages are copied to ensure that jank sensitive + * threads don't keep retrying for progress-critical + * pages. + */ + if (copied && mmap_lock_is_contended(dst_mm)) + break; + mmap_read_unlock(dst_mm); BUG_ON(!page); @@ -688,6 +697,9 @@ retry: if (fatal_signal_pending(current)) err = -EINTR; + + if (mmap_lock_is_contended(dst_mm)) + err = -EAGAIN; } if (err) break; |