[libpas] large_utility_aligned_allocator unconditionally calls give_back on allocation failure

[sosukesuzuki]

eccbe3f

[libpas] `large_utility_aligned_allocator` unconditionally calls give_back on allocation failure
https://bugs.webkit.org/show_bug.cgi?id=314368

Reviewed by Yusuke Suzuki.

large_utility_aligned_allocator's setup path only calls
pas_physical_page_sharing_pool_take_later when
pas_large_utility_free_heap_talks_to_large_sharing_pool is set, but the
failure path called pas_physical_page_sharing_pool_give_back
unconditionally. With the flag off, every failed allocation drifts
pas_physical_page_sharing_pool_balance upward by aligned_size, hiding
reclaimable pages from the scavenger.

Add the missing guard and a regression test that drives the failure path
with an always-failing memory source and checks the balance stays at zero
in both flag states.

* Source/bmalloc/libpas/src/libpas/pas_large_free_heap_helpers.c:
(large_utility_aligned_allocator):
* Source/bmalloc/libpas/src/test/LargeFreeHeapTests.cpp:
(std::failingMemorySource):
(std::testGiveBackGuardOnAllocationFailure):
(addLargeFreeHeapTests):

Canonical link: https://commits.webkit.org/312942@main

e952e5a

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	❌ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 api-mac-debug	✅ 🛠 gtk3-libwebrtc
✅ 🛠 🧪 jsc	✅ 🧪 api-ios	✅ 🧪 mac-wk1	✅ 🛠 gtk
✅ 🛠 🧪 jsc-debug-arm64		✅ 🧪 mac-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 api-gtk
✅ 🛠 🧪 merge	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🛠 playstation
	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2	✅ 🛠 jsc-armv7
	✅ 🛠 tv		✅ 🧪 jsc-armv7-tests
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash e952e5a)

Details

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	❌ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 api-mac-debug	✅ 🛠 gtk3-libwebrtc
✅ 🛠 🧪 jsc	✅ 🧪 api-ios	✅ 🧪 mac-wk1	✅ 🛠 gtk
✅ 🛠 🧪 jsc-debug-arm64		✅ 🧪 mac-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 api-gtk
✅ 🛠 🧪 merge	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🛠 playstation
	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2	✅ 🛠 jsc-armv7
	✅ 🛠 tv		✅ 🧪 jsc-armv7-tests
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[Constellation]

r=me
While pas_large_utility_free_heap_talks_to_large_sharing_pool is always true on the actual production environment, anyway, this is nice to fix!

[webkit-commit-queue]

Committed 312942@main (eccbe3f): https://commits.webkit.org/312942@main

Reviewed commits have been landed. Closing PR #64521 and removing active labels.