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[79.242.57.127]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42ca3a3cc31sm94306155e9.24.2024.09.09.01.04.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Sep 2024 01:04:43 -0700 (PDT) Message-ID: <2bb87247-9212-426b-aaa7-e101f25d38ca@redhat.com> Date: Mon, 9 Sep 2024 10:04:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -v3 2/3] resource: Make alloc_free_mem_region() works for iomem_resource To: "Huang, Ying" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, Dan Williams , Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Ira Weiny , Alistair Popple , Andy Shevchenko , Bjorn Helgaas , Baoquan He References: <20240906030713.204292-1-ying.huang@intel.com> <20240906030713.204292-3-ying.huang@intel.com> <28bbd51b-cc47-4468-9523-45dab25d20dd@redhat.com> <878qw11f05.fsf@yhuang6-desk2.ccr.corp.intel.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ij6gg3kkz4dqoouaeikkgsgh3ueqtc14 X-Rspamd-Queue-Id: 29D0C40010 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1725869087-864572 X-HE-Meta: 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 /KnQbDRB 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09.09.24 09:07, Huang, Ying wrote: > Hi, David, > > David Hildenbrand writes: > >> On 06.09.24 05:07, Huang Ying wrote: >>> During developing a kunit test case for region_intersects(), some fake >>> resources need to be inserted into iomem_resource. To do that, a >>> resource hole needs to be found first in iomem_resource. >>> However, alloc_free_mem_region() cannot work for iomem_resource now. >>> Because the start address to check cannot be 0 to detect address >>> wrapping 0 in gfr_continue(), while iomem_resource.start == 0. To >>> make alloc_free_mem_region() works for iomem_resource, gfr_start() is >>> changed to avoid to return 0 even if base->start == 0. We don't need >>> to check 0 as start address. >>> Signed-off-by: "Huang, Ying" >>> Cc: Dan Williams >>> Cc: David Hildenbrand >>> Cc: Davidlohr Bueso >>> Cc: Jonathan Cameron >>> Cc: Dave Jiang >>> Cc: Alison Schofield >>> Cc: Vishal Verma >>> Cc: Ira Weiny >>> Cc: Alistair Popple >>> Cc: Andy Shevchenko >>> Cc: Bjorn Helgaas >>> Cc: Baoquan He >>> --- >>> kernel/resource.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> diff --git a/kernel/resource.c b/kernel/resource.c >>> index 235dc77f8add..035ef16c1a66 100644 >>> --- a/kernel/resource.c >>> +++ b/kernel/resource.c >>> @@ -1873,7 +1873,7 @@ static resource_size_t gfr_start(struct resource *base, resource_size_t size, >>> return end - size + 1; >>> } >>> - return ALIGN(base->start, align); >> >> You should add a comment here. But I do find what you are doing here >> quite confusing. > > Sure. And sorry for confusing words. > >> Above you write: "We don't need to check 0 as start address." -- why? >> To make the code extra confusing? :) > > After the change, we will not return "0" from gfr_start(). So we cannot > check "0" as start address. And I think nobody need to check "0", so it > should be OK to do that. > >> /* Never return address 0, because XXX. */ >> if (!base->start) >> return align; >> return ALIGN(base->start, align); >> >> >> And i still haven't understood XXX. For whom exactly is address 0 a problem? > > Because the following lines in gfr_continue() > > /* > * In the ascend case be careful that the last increment by > * @size did not wrap 0. > */ > return addr > addr - size && > addr <= min_t(resource_size_t, base->end, > (1ULL << MAX_PHYSMEM_BITS) - 1); > > If addr == 0, then addr < addr - size. gfr_continue() will return > false, and we will not check any address. Thanks, that makes things cleaner. I think it might be better to just rework the retying logic, to detect wraps based on the old and new address. That would require a bit more work, something like that should probably handle all possible corner case. Dan wrote that code, so I'll leave it up to him to decide how to handle that :) diff --git a/kernel/resource.c b/kernel/resource.c index 9f747bb7cd031..2cd054c8277e8 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1819,40 +1819,48 @@ EXPORT_SYMBOL(resource_list_free); #define GFR_REQUEST_REGION (1UL << 1) #define GFR_DEFAULT_ALIGN (1UL << PA_SECTION_SHIFT) -static resource_size_t gfr_start(struct resource *base, resource_size_t size, - resource_size_t align, unsigned long flags) +static bool gfr_start(struct resource *base, resource_size_t *addr, + resource_size_t size, resource_size_t align, unsigned long flags) { + resource_size_t start_addr; + if (flags & GFR_DESCENDING) { resource_size_t end; end = min_t(resource_size_t, base->end, (1ULL << MAX_PHYSMEM_BITS) - 1); - return end - size + 1; + start_addr = end - size + 1; + if (start_addr > end || start_addr < base->start) + return false; + } else { + start_addr = ALIGN(base->start, align); + if (start_addr < base->start || start_addr > base->end) + return false; } - - return ALIGN(base->start, align); + *addr = start_addr; + return true; } -static bool gfr_continue(struct resource *base, resource_size_t addr, - resource_size_t size, unsigned long flags) +static bool gfr_continue(struct resource *base, resource_size_t *addr, + resource_size_t align, unsigned long flags) { - if (flags & GFR_DESCENDING) - return addr > size && addr >= base->start; - /* - * In the ascend case be careful that the last increment by - * @size did not wrap 0. - */ - return addr > addr - size && - addr <= min_t(resource_size_t, base->end, - (1ULL << MAX_PHYSMEM_BITS) - 1); -} + resource_size_t new_addr; -static resource_size_t gfr_next(resource_size_t addr, resource_size_t size, - unsigned long flags) -{ - if (flags & GFR_DESCENDING) - return addr - size; - return addr + size; + if (flags & GFR_DESCENDING) { + new_addr = *addr - align; + if (new_addr > *addr || new_addr < base->start) + return false; + } else { + resource_size_t end; + + end = min_t(resource_size_t, base->end, + (1ULL << MAX_PHYSMEM_BITS) - 1); + new_addr = *addr + align; + if (new_addr < *addr || new_addr > end) + return false; + } + *addr = new_addr; + return true; } static void remove_free_mem_region(void *_res) @@ -1893,9 +1901,9 @@ get_free_mem_region(struct device *dev, struct resource *base, } write_lock(&resource_lock); - for (addr = gfr_start(base, size, align, flags); - gfr_continue(base, addr, align, flags); - addr = gfr_next(addr, align, flags)) { + if (!gfr_start(base, &addr, size, align, flags)) + goto unlock; + do { if (__region_intersects(base, addr, size, 0, IORES_DESC_NONE) != REGION_DISJOINT) continue; @@ -1939,7 +1947,8 @@ get_free_mem_region(struct device *dev, struct resource *base, } return res; - } + } while (gfr_continue(base, &addr, align, flags)); +unlock: write_unlock(&resource_lock); if (flags & GFR_REQUEST_REGION) { -- 2.46.0 -- Cheers, David / dhildenb