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([2409:40c1:2022:5af0:565b:1ce7:b5ad:c8ae]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c825378fd56sm2014106a12.8.2026.05.07.04.49.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 May 2026 04:49:20 -0700 (PDT) From: Jill Ravaliya To: akpm@linux-foundation.org, urezki@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jill Ravaliya Subject: [PATCH 1/2] mm/vmalloc: free unused pages when shrinking vrealloc() allocation Date: Thu, 7 May 2026 17:18:53 +0530 Message-ID: <20260507114854.41117-1-jillravaliya@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A157F4000F X-Rspam-User: X-Stat-Signature: m4yhet1ztzjhxcmwx5s45h6c1tc4nn8r X-HE-Tag: 1778154562-528026 X-HE-Meta: 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 537+6Uy7 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: vrealloc() shrink path zeros unused memory and updates vm->requested_size, but never frees the physical pages, removes page table mappings, or flushes the TLB for the unused range. When a caller shrinks a vmalloc allocation, physical pages backing the unused portion remain allocated until vfree() is eventually called, wasting real RAM. Fix this by unmapping the unused virtual range using vunmap_range() which also flushes the TLB, freeing each unused physical page back to the buddy allocator, and updating vm->nr_pages to reflect the new page count. Signed-off-by: Jill Ravaliya --- mm/vmalloc.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index aa08651ec..a8cedfc5d 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4336,6 +4336,27 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align memset((void *)p + size, 0, old_size - size); vm->requested_size = size; kasan_vrealloc(p, old_size, size); + + /* Shrink the vm_area: unmap and free unused pages. */ + if (size < alloced_size) { + unsigned long new_nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT; + unsigned long i; + + /* Unmap unused virtual range and flush TLB. */ + vunmap_range((unsigned long)p + PAGE_ALIGN(size), + (unsigned long)p + alloced_size); + + /* Free unused physical pages back to buddy allocator. */ + for (i = new_nr_pages; i < vm->nr_pages; i++) { + mod_lruvec_page_state(vm->pages[i], + NR_VMALLOC, -1); + __free_page(vm->pages[i]); + vm->pages[i] = NULL; + } + + vm->nr_pages = new_nr_pages; + } + return (void *)p; } -- 2.43.0