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charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIABwOuWkC/3XOwU7EIBDG8VfZcBYzTAHbPfkexgOUwU7sFgOGq Ju+u+yeaojH/yTfL3MVhTJTEefTVWSqXDhtLczDScyL295IcmgtENDCACjrxa1rmmVZMm/vErT H6Ow4OqVFG31kivx1B19eWy9cPlP+vvtV3a7/UlVJkNoGilFb45/o+Sct6eJ4feRN3LCKR0B3A DYAxxknFSwogB4YjsDUAUMDjJkghjEQku8BfQBU/4FuwKzaFLw32pi/wL7vvydWuwxxAQAA 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=1773735454; l=3389; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=RisNgPVkJ2DmLymS1Pnu8hBXRm1dphIY+WY3EUkz0dk=; b=vq8rG2UAkpSPEXrOKqhYAZXPkT4gBEYlpeIhxkGE+9c/VjX8AxjbATOPskhzKea5U6KtWKBwo FXHzsHuk6hCAw/2Pa0y968p1hcZpT2I/DAXRTtmtwk4sJf340RJY6aY 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-Queue-Id: 965D44000D X-Rspamd-Server: rspam07 X-Stat-Signature: jobdsf5e5bwz9ubgwo8b56q19ntik6sn X-Rspam-User: X-HE-Tag: 1773735459-189313 X-HE-Meta: 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 kpDbgbG3 w2eRgz0v48kKvxuEiMWJm/ZmOMiQe/Pp6ChkoUu1DufvH4I5NBcR9Mb9j02R2enGMdMis+s5AZLYD1TZA2RJuwY+kzhjjU10ORDGbTST8RGMldlFUnmHl6//FLkE9e3J4j9jmHG7G53TFio4rKxOIKteAi6Yw/SwC3md5M1X2uTYCuJ2bLS5ZHcmakbnEuQXA85jMUk1iDMQaWNJCFcyBz6ZeJf7yhMqLhdIwh4HOenHXbPCobrgPzN7T6RhRd9YcFtCoxTRet/eTU1ZqGLkPkwW6ZXbk6T4sw1tELZuisq9pnad9QgVKIY4p2k8MZFNcdDTeQBMnG1a3aEMfMN4ikHaA1KdpzoIa8hyPHU6VP6qgJneNGcj5tuBBRrg1xJxK/IFs 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. Allocations with VM_FLUSH_RESET_PERMS are also skipped. 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 v5: - Skip vrealloc shrink for VM_FLUSH_RESET_PERMS (Uladzislau Rezki) - Link to v4: https://lore.kernel.org/r/20260314-vmalloc-shrink-v4-0-c1e2e0bb5455@zohomail.in 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 | 67 ++++++++++++++++++++++++++++++++++++++---------------- 2 files changed, 100 insertions(+), 19 deletions(-) --- base-commit: 7d47a508dfdc335c107fb00b4d9ef46488281a52 change-id: 20260302-vmalloc-shrink-04b2fa688a14 Best regards, -- Shivam Kalra