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b=InvYwEaia1IxbLmUgiGxnrWQRZ/rw2K4n0gteTimX4S4DUqQW627G5DkgcDXlU6et cEDQUQTNrDyjZif+fbxy0WDKsYJntWW/sBg1lzxTTYmMtMsV6b7/pX8jSvLqEC2L/b JxVtBmf3ejggShlMihKUo531xnJtIBknzfbaK9h5fec6uu2ni++CO8k3kV80JohozP J1UA6nLVlZeVkAqiqnJwClVZWd7Y3rd0kIF3jayLNAj2SzDGiSXmj91UuhTnVjJ54t 7bvZG1Oz7RkNLPtZFq5PKyXeZ+GGq4IP3fkQsdJUj00BfvLzIZigLnPRiyE0KtqEcG xxx+qhItT4rUQ== Date: Tue, 26 May 2026 17:38:24 +0300 From: Mike Rapoport To: David Laight Cc: Song Liu , Yu Kuai , Li Nan , Xiao Ni , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-raid@vger.kernel.org Subject: Re: [PATCH 2/2] lib/raid6: use kmalloc() in raid6_select_algo() Message-ID: References: <20260520-lib-v1-0-cb3045bef2d8@kernel.org> <20260520-lib-v1-2-cb3045bef2d8@kernel.org> <20260520140657.2b5b5f3b@pumpkin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260520140657.2b5b5f3b@pumpkin> X-Rspamd-Server: rspam11 X-Stat-Signature: 6ag8hdkboq9oz8fhkdg679mb6bi716gk X-Rspamd-Queue-Id: 50F4920011 X-Rspam-User: X-HE-Tag: 1779806312-501564 X-HE-Meta: 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 VDvWkblk uZqQaDknG2XOclZtBJitrwUNrfh6CK0CvAOu0symXT1kCRTIb+T3F2NazVHWSbIfZ+Vs24y37ZWVBsPMwPGu5/bKohbRIKDmTlANV32/4EKll4PwhSzwRbI481zaKQS20cs5BTzlMIq8yUsdy/VIunCZOtlDNRJg1jiEnsZ0dX9QATGIqzcK2/hWVBJZriVOk2cnBCqo0oxS6v2GKpf0IMSq31fPjLGpI1ERGy67j0n8VdDliorlNZVehyS/vqPhsZQusMvDJs456rv/qR3iG/HXpafB0rnO4w7758BozvrTJNtYUQwgAbrgeYMaec3hgKXElAcEeYBzoxiJagXR33M+nCQty9tRN6lzDen8Wm7mYUzJnIQT7iC9n0/o7ak/nKXhHgSvb/vk4BVTyxO0+ejCT8eVBj5bjwD1z Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, May 20, 2026 at 02:06:57PM +0100, David Laight wrote: > On Wed, 20 May 2026 11:17:52 +0300 > "Mike Rapoport (Microsoft)" wrote: > > > raid6_select_algo() allocates an order 3 (8 pages) buffer that is used > > as a scratch area for selection of the best algorithm. > > Should this code really be using a 4k buffer rather than a PAGE_SIZE one? Why? > -- David > > > > > For such large allocations kmalloc() would fall back to alloc_pages() but > > still kmalloc() is a better API as it does not require unnecessary > > castings and may provide more debugging possibilities. > > > > Replace __get_free_pages() call with kmalloc(). > > > > Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com > > Signed-off-by: Mike Rapoport (Microsoft) > > --- > > lib/raid6/algos.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c > > index 799e0e5eac26..89e627c62e30 100644 > > --- a/lib/raid6/algos.c > > +++ b/lib/raid6/algos.c > > @@ -12,6 +12,7 @@ > > */ > > > > #include > > +#include > > #ifndef __KERNEL__ > > #include > > #include > > @@ -129,7 +130,6 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = { > > #endif > > > > #define RAID6_TEST_DISKS 8 > > -#define RAID6_TEST_DISKS_ORDER 3 > > > > static inline const struct raid6_recov_calls *raid6_choose_recov(void) > > { > > @@ -250,7 +250,7 @@ int __init raid6_select_algo(void) > > int i, cycle; > > > > /* prepare the buffer and fill it circularly with gfmul table */ > > - disk_ptr = (char *)__get_free_pages(GFP_KERNEL, RAID6_TEST_DISKS_ORDER); > > + disk_ptr = kmalloc(PAGE_SIZE * RAID6_TEST_DISKS, GFP_KERNEL); > > if (!disk_ptr) { > > pr_err("raid6: Yikes! No memory available.\n"); > > return -ENOMEM; > > @@ -275,7 +275,7 @@ int __init raid6_select_algo(void) > > /* select raid recover functions */ > > rec_best = raid6_choose_recov(); > > > > - free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER); > > + kfree(disk_ptr); > > > > return gen_best && rec_best ? 0 : -EINVAL; > > } > > > > -- Sincerely yours, Mike.