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charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAIwktWkC/3XMza7CIBCG4VsxrMUMU8ppXXkfxgUtw+nEWgwY4 k9676IrTePy/ZLveYhEkSmJ7eohImVOHKYSer0S/WCnf5LsSgsENFABynyy4xh6mYbI01GC7tB b0zRWaVFO50ier29wfyg9cLqEeHv7Wb3Wn1RWEqQ2jrzXpu7+aHcPQzhZHjc8iReW8RPQCwALg E2PrXIGFMASqD6BdgFUBajrFrxrHCF138A8z0/7/oNpMAEAAA== X-Change-ID: 20260302-vmalloc-shrink-04b2fa688a14 To: Andrew Morton , Uladzislau Rezki Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alice Ryhl , Danilo Krummrich , Shivam Kalra X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1773479164; l=3149; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=FpWmOp0KrMNBjh4gR56azZfEz9z4IdeZPVymGFzqY4k=; b=e2prkkhIrcliRDFynHQBoXYTe7vpo2xtunw0OR910D+c/ibdQa4FAC33JhJx9Dnw8+zWOfr2I 7gP21Z3WRcJBPU2CGo4ZHCBDBbZ2zMk/fnYzChdxC5pZZZxefIbyydi X-Developer-Key: i=shivamkalra98@zohomail.in; a=ed25519; pk=9Q+S1LD/xjbjL7bEaLIlwRADBwU/6LJq7lYm8LFrkQE= X-Endpoint-Received: by B4 Relay for shivamkalra98@zohomail.in/20260212 with auth_id=633 X-Original-From: Shivam Kalra Reply-To: shivamkalra98@zohomail.in X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0411B40011 X-Stat-Signature: m5wzx16xhkepmaow6cbk1g1zcbij6t1t X-Rspam-User: X-HE-Tag: 1773479167-377491 X-HE-Meta: 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 8QltZBID LSEjrgymQD+jvh/SkM+0I2UFBZTZzgNxeN1631vGguMUKsoE+z2l7IdWIKmkbubF/djGMqBlXNdwKarln56EVG20q2eMYaJcDaJKGwu2tixZ2cUb8sFLj8Jjei4fULprvgtg/3JE6/KAa2sdpw0gZ12hP6+G7+AN5LWtO3Tb3vKpzNYB7AfkGxfCxbTJdIetBtIPA03T7tirOt4vma2C5dId47mb9aC7dZwk0VGA3uwWiEztfXVorKCDEyVqrz09pXRvuCAHUWd0l5EBfL4hWAbFU+RWtYBGm571glVcqCB8gqb0LU5+VeoJ6SG5shw/nVK6rtAtuvDAGT8XeE499bargJCBAibD0OlPpqnVyrPfiMPbHI8heYFT9Pnye9XW38mbz Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This series implements the TODO in vrealloc() to unmap and free unused pages when shrinking across a page boundary. Problem: When vrealloc() shrinks an allocation, it updates bookkeeping (requested_size, KASAN shadow) but does not free the underlying physical pages. This wastes memory for the lifetime of the allocation. Solution: - Patch 1: Extracts a vm_area_free_pages(vm, start, end) helper from vfree() that frees a range of pages with memcg and nr_vmalloc_pages accounting. Freed page pointers are set to NULL to prevent stale references. - Patch 2: Uses the helper to free tail pages when vrealloc() shrinks across a page boundary. Skips huge page allocations (page_order > 0) since compound pages cannot be partially freed. Also fixes the grow-in-place path to check vm->nr_pages instead of get_vm_area_size(), which reflects the virtual reservation and does not change on shrink. - Patch 3: Adds a vrealloc test case to lib/test_vmalloc that exercises grow-realloc, shrink-across-boundary, shrink-within-page, and grow-in-place paths with data integrity validation. The virtual address reservation is kept intact to preserve the range for potential future grow-in-place support. A concrete user is the Rust binder driver's KVVec::shrink_to [1], which performs explicit vrealloc() shrinks for memory reclamation. Tested: - KASAN KUnit (vmalloc_oob passes) - lib/test_vmalloc stress tests (3/3, 1M iterations each) - checkpatch, sparse, W=1, allmodconfig, coccicheck clean [1] https://lore.kernel.org/all/20260216-binder-shrink-vec-v3-v6-0-ece8e8593e53@zohomail.in/ Signed-off-by: Shivam Kalra --- Changes in v4: - Rename vmalloc_free_pages() to vm_area_free_pages() to align with vm_area_alloc_pages() (Uladzislau Rezki) - NULL out freed vm->pages[] entries to prevent stale pointers (Alice Ryhl) - Remove redundant if (vm->nr_pages) guard in vfree() (Uladzislau Rezki) - Add vrealloc test case to lib/test_vmalloc (new patch 3/3) - Link to v3: https://lore.kernel.org/r/20260309-vmalloc-shrink-v3-0-5590fd8de2eb@zohomail.in Changes in v3: - Restore the comment. - Rebase to the latest mm-new - Link to v2: https://lore.kernel.org/r/20260304-vmalloc-shrink-v2-0-28c291d60100@zohomail.in Changes in v2: - Updated the base-commit to mm-new - Fix conflicts after rebase - Ran `clang-format` on the changes made - Use a single `kasan_vrealloc` (Alice Ryhl) - Link to v1: https://lore.kernel.org/r/20260302-vmalloc-shrink-v1-0-46deff465b7e@zohomail.in --- Shivam Kalra (3): mm/vmalloc: extract vm_area_free_pages() helper from vfree() mm/vmalloc: free unused pages on vrealloc() shrink lib/test_vmalloc: add vrealloc test case lib/test_vmalloc.c | 52 ++++++++++++++++++++++++++++++++++++++++++ mm/vmalloc.c | 66 ++++++++++++++++++++++++++++++++++++++---------------- 2 files changed, 99 insertions(+), 19 deletions(-) --- base-commit: 593fab843afbd6800243552aebcc61d02d3cdcb2 change-id: 20260302-vmalloc-shrink-04b2fa688a14 Best regards, -- Shivam Kalra