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Howlett" , Vlastimil Babka , Harry Yoo , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250619075040.796047-1-ye.liu@linux.dev> <9454603f-c187-4386-8244-69f304197954@arm.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ye Liu In-Reply-To: <9454603f-c187-4386-8244-69f304197954@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A204E4000F X-Stat-Signature: qfztqepja3mkqqwdniy84ga55wu56udh X-Rspam-User: X-HE-Tag: 1750321754-635712 X-HE-Meta: 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 P0FhYThi XOdVX7LqO5FaOltWAzVNOBYkr2mOrtttk3/cm8aXejv6MR3YfOhOWSgKgpHE3kvnaKXj7zvUOdOU2SGNwYzRAhgJxl9YxpWvEDY2nS1/3Uz+DW8HFgSP+fe8GWpGaC/sZVGCQ9MqAHpYiv6OvP/bzHkky1oBGMQa9CNsjT7CXxoL4riZlZnUAbSo757Zl3qmTYbjYJIOz9lrmiV8MAr7wpBclj3c1EscxjwUVY9nUykZZGnycJnPIzW9J5OJqBdf6hOkwFUIrg05eDlzdyd4R+46Stfsx000De1+s 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: Hi Lorenzo and Dev, Thanks for your feedback. I understand all your points and will drop this patch. Best regards, Ye Liu On 2025/6/19 16:17, Dev Jain wrote: > > On 19/06/25 1:20 pm, Ye Liu wrote: >> From: Ye Liu >> >> Add NULL pointer checks for rmap_one callback in rmap_walk operations >> to prevent potential NULL pointer dereferences. Also clean up some >> code by removing redundant comments and caching folio_nr_pages(). >> >> Signed-off-by: Ye Liu >> --- > > Don't really see the point of this patch. The rmap_one call back will > always be there as we need a way to define how to unmap/do the reverse > map walk for one VMA at a time. And the folio_nr_pages() will probably > get cached by the compiler anyways. > >>   mm/ksm.c  |  2 +- >>   mm/rmap.c | 14 +++++++------- >>   2 files changed, 8 insertions(+), 8 deletions(-) >> >> diff --git a/mm/ksm.c b/mm/ksm.c >> index 18b3690bb69a..22ad069d1860 100644 >> --- a/mm/ksm.c >> +++ b/mm/ksm.c >> @@ -3068,7 +3068,7 @@ void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc) >>               if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) >>                   continue; >>   -            if (!rwc->rmap_one(folio, vma, addr, rwc->arg)) { >> +            if (rwc->rmap_one && !rwc->rmap_one(folio, vma, addr, rwc->arg)) { >>                   anon_vma_unlock_read(anon_vma); >>                   return; >>               } >> diff --git a/mm/rmap.c b/mm/rmap.c >> index fb63d9256f09..17d43d104a0d 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1202,8 +1202,7 @@ int mapping_wrprotect_range(struct address_space *mapping, pgoff_t pgoff, >>       if (!mapping) >>           return 0; >>   -    __rmap_walk_file(/* folio = */NULL, mapping, pgoff, nr_pages, &rwc, >> -             /* locked = */false); >> +    __rmap_walk_file(NULL, mapping, pgoff, nr_pages, &rwc, false); >>         return state.cleaned; >>   } >> @@ -2806,6 +2805,7 @@ static void rmap_walk_anon(struct folio *folio, >>       struct anon_vma *anon_vma; >>       pgoff_t pgoff_start, pgoff_end; >>       struct anon_vma_chain *avc; >> +    unsigned long nr_pages; >>         if (locked) { >>           anon_vma = folio_anon_vma(folio); >> @@ -2817,13 +2817,13 @@ static void rmap_walk_anon(struct folio *folio, >>       if (!anon_vma) >>           return; >>   +    nr_pages = folio_nr_pages(folio); >>       pgoff_start = folio_pgoff(folio); >> -    pgoff_end = pgoff_start + folio_nr_pages(folio) - 1; >> +    pgoff_end = pgoff_start + nr_pages - 1; >>       anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, >>               pgoff_start, pgoff_end) { >>           struct vm_area_struct *vma = avc->vma; >> -        unsigned long address = vma_address(vma, pgoff_start, >> -                folio_nr_pages(folio)); >> +        unsigned long address = vma_address(vma, pgoff_start, nr_pages); >>             VM_BUG_ON_VMA(address == -EFAULT, vma); >>           cond_resched(); >> @@ -2831,7 +2831,7 @@ static void rmap_walk_anon(struct folio *folio, >>           if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) >>               continue; >>   -        if (!rwc->rmap_one(folio, vma, address, rwc->arg)) >> +        if (rwc->rmap_one && !rwc->rmap_one(folio, vma, address, rwc->arg)) >>               break; >>           if (rwc->done && rwc->done(folio)) >>               break; >> @@ -2894,7 +2894,7 @@ static void __rmap_walk_file(struct folio *folio, struct address_space *mapping, >>           if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) >>               continue; >>   -        if (!rwc->rmap_one(folio, vma, address, rwc->arg)) >> +        if (rwc->rmap_one && !rwc->rmap_one(folio, vma, address, rwc->arg)) >>               goto done; >>           if (rwc->done && rwc->done(folio)) >>               goto done;