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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477bf1f365fsm3763665e9.8.2025.11.20.10.44.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Nov 2025 10:44:11 -0800 (PST) Date: Thu, 20 Nov 2025 18:44:09 +0000 From: David Laight To: Bart Van Assche Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, "James E.J. Bottomley" , "Martin K. Petersen" Subject: Re: [PATCH 26/44] drivers/scsi: use min() instead of min_t() Message-ID: <20251120184409.67db1c25@pumpkin> In-Reply-To: <2a8c62e1-6e29-4ac6-b661-7b5ec1763288@acm.org> References: <20251119224140.8616-1-david.laight.linux@gmail.com> <20251119224140.8616-27-david.laight.linux@gmail.com> <2a8c62e1-6e29-4ac6-b661-7b5ec1763288@acm.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 19 Nov 2025 15:09:02 -0800 Bart Van Assche wrote: > On 11/19/25 2:41 PM, david.laight.linux@gmail.com wrote: > > From: David Laight > > > > min_t(unsigned int, a, b) casts an 'unsigned long' to 'unsigned int'. > > Use min(a, b) instead as it promotes any 'unsigned int' to 'unsigned long' > > and so cannot discard significant bits. > > > > In this case the 'unsigned long' value is small enough that the result > > is ok. > > > > Detected by an extra check added to min_t(). > > > > Signed-off-by: David Laight > > --- > > drivers/scsi/hosts.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c > > index 17173239301e..b15896560cf6 100644 > > --- a/drivers/scsi/hosts.c > > +++ b/drivers/scsi/hosts.c > > @@ -247,7 +247,7 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev, > > shost->dma_dev = dma_dev; > > > > if (dma_dev->dma_mask) { > > - shost->max_sectors = min_t(unsigned int, shost->max_sectors, > > + shost->max_sectors = min(shost->max_sectors, > > dma_max_mapping_size(dma_dev) >> SECTOR_SHIFT); > > } > > So instead of the type cast performed by min_t() potentially discarding > bits, the assignment potentially discards bits. I'm not sure this is an > improvement. The assignment cant discard bits because shost->max_sectors is also on the RHS. In any case you'd need a 2TB mapping size to get an error. That probably cant happen for other reasons. The patch is remove a false positive for a check added to min_t(T, a, b) that sizeof (b) <= sizeof (T). David > > Thanks, > > Bart. >