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charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAHRSxmkC/3XPy07DMBAF0F+pvMZoPPErXfEfqAs/xsQiTVCCo kKVf8fpysiwvCPdo7l3ttKSaWXn050ttOU1z1MJ9unEwuCmN+I5lswQUEMHyLerG8c58HVY8vT OQXpMTlvrhGSl9LFQyrcH+Hopecjr57x8PfxNHNd/qU1w4FJHSklq5Q29fM/DfHV5fM4TO7ANa 0A2ABYAbcBeRA0CoAW6GugboCuAUj2kaCMh+RaQFSDaD2QBgihV8F5JpVpA1YBpAFUA75NPSga F+g9AVwCKBtAFAI3BGW8CeWwBUwPtBHNMANLoLalou9/Avu8/RnKjjzQCAAA= 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=1774604917; l=5566; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=+TJvotV/1YDLcmByd8IU2fgFVMxaHE1F+vCxCRlc09c=; b=w0rxUYcQMKZaAz/3JxUGKLJy3ZCYctCWHyCgW4Q5EzLD31GSyDpeUBhVVGq0SCvdAVgxq1pgS bFuDYcx3bgnDTr7LmRw/vRIRjD/LyIejbcVO7KOIPc5hSmYPq2LyDGJ 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: rspam12 X-Stat-Signature: qc91p16hhdngfy6f34zh8yojccwy1gxo X-Rspamd-Queue-Id: 2D565A000D X-Rspam-User: X-HE-Tag: 1774604921-624748 X-HE-Meta: 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 5Jo9+qVN ix+LFNx70cOeThMyLsXgEAxLSLpjTBcBJFueOejGspdQq7MG8wzl/Q7Y5zeK0HwrRfAB2sPBIoXMPWhWczrSnCtQ9x2DoTYGGkUqlKPeCcm6FZ0hY9QTRcxpZLoPps0BRye8L8OwwiG8LVqzMcftRtLYs+ySnQHKTx2AxowHK3Nc180bvXK6zJXJW+TXiaOc56GXbJxCL0Mwmld0ViBgb0uVAJzObShAN+YH4DpZiDQ3YzJIGUuCd+n6mpHYH4L3BVA7mtpb7bvQoaqve1YKjlAeepmX1u1feGP011D0hM2cOqMkNw7YwyCpMO1mQg4WoPNjdLyPfLcgMYyTSzZNT4V6ZTjLjkS0tHNiLZm9u9T+XvaOKxdftfgwDRzoXuYifZO210uMV0cZMOLQf7FdSLyp5SNqI8czEE4Y8364Ik7X7TQoG/HiK+a4WLpoMGIgjc3Hx 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_idx, end_idx) 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: 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. This is a prerequisite for shrinking. - Patch 3: Zeros newly exposed memory on vrealloc() grow if __GFP_ZERO is requested, preventing stale data leaks from previously shrunk regions. - Patch 4: Protects /proc/vmallocinfo readers with READ_ONCE() to safely handle concurrent decreases to vm->nr_pages and NULL page pointers. - Patch 5: Uses the helper to free tail pages when vrealloc() shrinks across a page boundary. Skips huge page allocations, VM_FLUSH_RESET_PERMS, and VM_USERMAP. Updates Kmemleak tracking of the allocation. - Patch 6: Adds a vrealloc test case to lib/test_vmalloc that exercises grow-realloc, shrink-across-boundary, shrink-within-page, and grow-in-place paths. 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/ Suggested-by: Danilo Krummrich Signed-off-by: Shivam Kalra --- Changes in v8: - Strip the KASAN tag from the pointer before addr_to_node() to avoid acquiring the wrong node lock (Sashiko). - Rebase to latest mm-new. - Link to v7: https://lore.kernel.org/r/20260324-vmalloc-shrink-v7-0-c0e62b8e5d83@zohomail.in Changes in v7: - Fix NULL pointer dereference in shrink path (Sashiko) - Acquire vn->busy.lock when updating vm->nr_pages to synchronize with concurrent readers (Uladzislau Rezki) - Use READ_ONCE in vmalloc_dump_obj (Sashiko) - Skip shrink path on GFP_NIO or GFP_NOFS. (Sashiko) - Fix Overflow issue for large allocations. (Sashiko) - Use vrealloc instead of vmalloc in vrealloc test. - Link to v6: https://lore.kernel.org/r/20260321-vmalloc-shrink-v6-0-062ca7b7ceb2@zohomail.in Changes in v6: - Fix VM_USERMAP crash by explicitly bypassing early in the shrink path if the flag is set.(Sashiko) - Fix Kmemleak scanner panic by calling kmemleak_free_part() to update tracking on shrink.(Sashiko) - Fix /proc/vmallocinfo race condition by protecting vm->nr_pages access with READ_ONCE()/WRITE_ONCE() for concurrent readers.(Sashiko) - Fix stale data leak on grow-after-shrink by enforcing mandatory zeroing of the newly exposed memory.(Sashiko) - Fix memory leaks in vrealloc_test() by using a temporary pointer to preserve and free the original allocation upon failure.(Sashiko) - Rename vmalloc_free_pages parameters from start/end to start_idx/end_idx for better clarity.(Uladzislau Rezki) - Link to v5: https://lore.kernel.org/r/20260317-vmalloc-shrink-v5-0-bbfbf54c5265@zohomail.in - Link to Sashiko: https://sashiko.dev/#/patchset/20260317-vmalloc-shrink-v5-0-bbfbf54c5265%40zohomail.in 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 (6): mm/vmalloc: extract vm_area_free_pages() helper from vfree() mm/vmalloc: fix vrealloc() grow-in-place check mm/vmalloc: zero newly exposed memory on vrealloc() grow mm/vmalloc: use READ_ONCE() for vmalloc nr_pages status readers mm/vmalloc: free unused pages on vrealloc() shrink lib/test_vmalloc: add vrealloc test case lib/test_vmalloc.c | 62 +++++++++++++++++++++++ mm/vmalloc.c | 143 ++++++++++++++++++++++++++++++++++++++++++----------- 2 files changed, 175 insertions(+), 30 deletions(-) --- base-commit: f46991f1780ef97efff3b668627b763581032067 change-id: 20260302-vmalloc-shrink-04b2fa688a14 Best regards, -- Shivam Kalra