From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754082AbcDKLKV (ORCPT ); Mon, 11 Apr 2016 07:10:21 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35027 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753476AbcDKLIl (ORCPT ); Mon, 11 Apr 2016 07:08:41 -0400 From: Michal Hocko To: Cc: Andrew Morton , LKML , Michal Hocko , "Theodore Ts'o" Subject: [PATCH 19/19] jbd2: get rid of superfluous __GFP_REPEAT Date: Mon, 11 Apr 2016 13:08:12 +0200 Message-Id: <1460372892-8157-20-git-send-email-mhocko@kernel.org> X-Mailer: git-send-email 2.8.0.rc3 In-Reply-To: <1460372892-8157-1-git-send-email-mhocko@kernel.org> References: <1460372892-8157-1-git-send-email-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko jbd2_alloc is explicit about its allocation preferences wrt. the allocation size. Sub page allocations go to the slab allocator and larger are using either the page allocator or vmalloc. This is all good but the logic is unnecessarily complex. 1) as per Ted, the vmalloc fallback is a left-over: : jbd2_alloc is only passed in the bh->b_size, which can't be > : PAGE_SIZE, so the code path that calls vmalloc() should never get : called. When we conveted jbd2_alloc() to suppor sub-page size : allocations in commit d2eecb039368, there was an assumption that it : could be called with a size greater than PAGE_SIZE, but that's : certaily not true today. Moreover vmalloc allocation might even lead to a deadlock because the callers expect GFP_NOFS context while vmalloc is GFP_KERNEL. 2) __GFP_REPEAT for requests <= PAGE_ALLOC_COSTLY_ORDER is ignored since the flag was introduced. Let's simplify the code flow and use the slab allocator for sub-page requests and the page allocator for others. Even though order > 0 is not currently used as per above leave that option open. Cc: "Theodore Ts'o" Signed-off-by: Michal Hocko --- fs/jbd2/journal.c | 32 +++++++------------------------- 1 file changed, 7 insertions(+), 25 deletions(-) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 435f0b26ac20..bd7c31d8c05e 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -2328,18 +2328,10 @@ void *jbd2_alloc(size_t size, gfp_t flags) BUG_ON(size & (size-1)); /* Must be a power of 2 */ - flags |= __GFP_REPEAT; - if (size == PAGE_SIZE) - ptr = (void *)__get_free_pages(flags, 0); - else if (size > PAGE_SIZE) { - int order = get_order(size); - - if (order < 3) - ptr = (void *)__get_free_pages(flags, order); - else - ptr = vmalloc(size); - } else + if (size < PAGE_SIZE) ptr = kmem_cache_alloc(get_slab(size), flags); + else + ptr = (void *)__get_free_pages(flags, get_order(size)); /* Check alignment; SLUB has gotten this wrong in the past, * and this can lead to user data corruption! */ @@ -2350,20 +2342,10 @@ void *jbd2_alloc(size_t size, gfp_t flags) void jbd2_free(void *ptr, size_t size) { - if (size == PAGE_SIZE) { - free_pages((unsigned long)ptr, 0); - return; - } - if (size > PAGE_SIZE) { - int order = get_order(size); - - if (order < 3) - free_pages((unsigned long)ptr, order); - else - vfree(ptr); - return; - } - kmem_cache_free(get_slab(size), ptr); + if (size < PAGE_SIZE) + kmem_cache_free(get_slab(size), ptr); + else + free_pages((unsigned long)ptr, get_order(size)); }; /* -- 2.8.0.rc3 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f54.google.com (mail-wm0-f54.google.com [74.125.82.54]) by kanga.kvack.org (Postfix) with ESMTP id E3F6C6B0005 for ; Mon, 11 Apr 2016 07:14:12 -0400 (EDT) Received: by mail-wm0-f54.google.com with SMTP id v188so81693300wme.1 for ; Mon, 11 Apr 2016 04:14:12 -0700 (PDT) Received: from mail-wm0-f66.google.com (mail-wm0-f66.google.com. [74.125.82.66]) by mx.google.com with ESMTPS id xy1si26291424wjc.0.2016.04.11.04.08.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Apr 2016 04:08:40 -0700 (PDT) Received: by mail-wm0-f66.google.com with SMTP id l6so20397625wml.3 for ; Mon, 11 Apr 2016 04:08:40 -0700 (PDT) From: Michal Hocko Subject: [PATCH 19/19] jbd2: get rid of superfluous __GFP_REPEAT Date: Mon, 11 Apr 2016 13:08:12 +0200 Message-Id: <1460372892-8157-20-git-send-email-mhocko@kernel.org> In-Reply-To: <1460372892-8157-1-git-send-email-mhocko@kernel.org> References: <1460372892-8157-1-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Andrew Morton , LKML , Michal Hocko , Theodore Ts'o From: Michal Hocko jbd2_alloc is explicit about its allocation preferences wrt. the allocation size. Sub page allocations go to the slab allocator and larger are using either the page allocator or vmalloc. This is all good but the logic is unnecessarily complex. 1) as per Ted, the vmalloc fallback is a left-over: : jbd2_alloc is only passed in the bh->b_size, which can't be > : PAGE_SIZE, so the code path that calls vmalloc() should never get : called. When we conveted jbd2_alloc() to suppor sub-page size : allocations in commit d2eecb039368, there was an assumption that it : could be called with a size greater than PAGE_SIZE, but that's : certaily not true today. Moreover vmalloc allocation might even lead to a deadlock because the callers expect GFP_NOFS context while vmalloc is GFP_KERNEL. 2) __GFP_REPEAT for requests <= PAGE_ALLOC_COSTLY_ORDER is ignored since the flag was introduced. Let's simplify the code flow and use the slab allocator for sub-page requests and the page allocator for others. Even though order > 0 is not currently used as per above leave that option open. Cc: "Theodore Ts'o" Signed-off-by: Michal Hocko --- fs/jbd2/journal.c | 32 +++++++------------------------- 1 file changed, 7 insertions(+), 25 deletions(-) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 435f0b26ac20..bd7c31d8c05e 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -2328,18 +2328,10 @@ void *jbd2_alloc(size_t size, gfp_t flags) BUG_ON(size & (size-1)); /* Must be a power of 2 */ - flags |= __GFP_REPEAT; - if (size == PAGE_SIZE) - ptr = (void *)__get_free_pages(flags, 0); - else if (size > PAGE_SIZE) { - int order = get_order(size); - - if (order < 3) - ptr = (void *)__get_free_pages(flags, order); - else - ptr = vmalloc(size); - } else + if (size < PAGE_SIZE) ptr = kmem_cache_alloc(get_slab(size), flags); + else + ptr = (void *)__get_free_pages(flags, get_order(size)); /* Check alignment; SLUB has gotten this wrong in the past, * and this can lead to user data corruption! */ @@ -2350,20 +2342,10 @@ void *jbd2_alloc(size_t size, gfp_t flags) void jbd2_free(void *ptr, size_t size) { - if (size == PAGE_SIZE) { - free_pages((unsigned long)ptr, 0); - return; - } - if (size > PAGE_SIZE) { - int order = get_order(size); - - if (order < 3) - free_pages((unsigned long)ptr, order); - else - vfree(ptr); - return; - } - kmem_cache_free(get_slab(size), ptr); + if (size < PAGE_SIZE) + kmem_cache_free(get_slab(size), ptr); + else + free_pages((unsigned long)ptr, get_order(size)); }; /* -- 2.8.0.rc3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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