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Petersen" Cc: Brian King , Hannes Reinecke , "James E.J. Bottomley" , Matthew Wilcox , Wen Xiong , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, Hannes Reinecke , John Garry Subject: Re: [PATCH v2 0/4] scsi: replace __get_free_pages() with kmalloc() Message-ID: References: <20260704-b4-scsi-v2-0-7d2d21a810de@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260704-b4-scsi-v2-0-7d2d21a810de@kernel.org> X-Rspamd-Queue-Id: 879FF14000C X-Stat-Signature: ce7idttse1g8huuzwpbxw1ybq4q5upnm X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1784551436-201934 X-HE-Meta: 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 M+FkuVFz 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Gentle ping. On Sat, Jul 04, 2026 at 09:13:33AM +0300, Mike Rapoport (Microsoft) wrote: > This is a (small) part of larger work of replacing page allocator calls > with kmalloc. > > My initial intention a few month ago was to remove ugly casts [1], but then > willy pointed out that Linus objected to something like this [2] and it > looks like more than a decade old technical debt. > > Largely, anything that doesn't need struct page (or a memdesc in the > future) should just use kmalloc() or kvmalloc() to allocate memory. > kmalloc() guarantees alignment, physical contiguity and working > virt_to_phys() and beside nicer API that returns void * on alloc and > doesn't require to know the allocation size on free, kmalloc() provides > better debugging capabilities than page allocator. > > Another thing is that touching these allocation sites gives the reviewers > opportunity to see if a PAGE_SIZE buffer is actually needed or maybe > another size is appropriate. > > For larger allocations that don't need physically contiguous memory > kvmalloc() can be a better option that __get_free_pages() because under > memory pressure it's is easier to allocate several order-0 pages than a > physically contiguous chunk with the same number of pages. > > And last, but not least, removing needless calls to page allocator should > help with memdesc (aka project folio) conversion. There will be way less > places to audit to see if the user was actually using struct page. > > Also in git: > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/scsi > > [1] https://lore.kernel.org/all/20251018093002.3660549-1-rppt@kernel.org/ > [2] https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@mail.gmail.com/ > > --- > v2 changes: > * replace GFP_ATOMIC with GFP_NOIO in ipr driver > > v1: https://patch.msgid.link/20260630-b4-scsi-v1-0-494fb37ebe7b@kernel.org > > --- > Mike Rapoport (Microsoft) (4): > scsi: target: file: use kmalloc() to allocate temporary protection buffer > scsi: proc: use kmalloc() in proc writers > scsi: ipr: use kmalloc() to allocate IPR dump buffer memory > scsi: sym53c8xx_2: replace __get_free_pages() with kmalloc() > > drivers/scsi/ipr.c | 4 ++-- > drivers/scsi/scsi_devinfo.c | 5 +++-- > drivers/scsi/scsi_proc.c | 9 +++++---- > drivers/scsi/sym53c8xx_2/sym_hipd.h | 4 ++-- > drivers/target/target_core_file.c | 4 ++-- > 5 files changed, 14 insertions(+), 12 deletions(-) > --- > base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 > change-id: 20260611-b4-scsi-d0b0eb4895f4 > > -- > Sincerely yours, > Mike. > -- Sincerely yours, Mike.