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From:   Michel Lespinasse <michel@lespinasse.org>
To:     Linux-MM <linux-mm@kvack.org>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     kernel-team@fb.com, Laurent Dufour <ldufour@linux.ibm.com>,
        Jerome Glisse <jglisse@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Michal Hocko <mhocko@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Matthew Wilcox <willy@infradead.org>,
        Liam Howlett <liam.howlett@oracle.com>,
        Rik van Riel <riel@surriel.com>,
        Paul McKenney <paulmck@kernel.org>,
        Song Liu <songliubraving@fb.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Minchan Kim <minchan@google.com>,
        Joel Fernandes <joelaf@google.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Michel Lespinasse <michel@lespinasse.org>
Subject: [PATCH v2 09/35] mm: add do_handle_mm_fault()
Date:   Fri, 28 Jan 2022 05:09:40 -0800
Message-Id: <20220128131006.67712-10-michel@lespinasse.org>
In-Reply-To: <20220128131006.67712-1-michel@lespinasse.org>
References: <20220128131006.67712-1-michel@lespinasse.org>
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Add a new do_handle_mm_fault function, which extends the existing
handle_mm_fault() API by adding an mmap sequence count, to be used
in the FAULT_FLAG_SPECULATIVE case.

In the initial implementation, FAULT_FLAG_SPECULATIVE always fails
(by returning VM_FAULT_RETRY).

The existing handle_mm_fault() API is kept as a wrapper around
do_handle_mm_fault() so that we do not have to immediately update
every handle_mm_fault() call site.

Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
---
 include/linux/mm.h | 12 +++++++++---
 mm/memory.c        | 10 +++++++---
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7f7aa3f0a396..4600dbb98cef 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1851,9 +1851,15 @@ int generic_error_remove_page(struct address_space *mapping, struct page *page);
 int invalidate_inode_page(struct page *page);
 
 #ifdef CONFIG_MMU
-extern vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
-				  unsigned long address, unsigned int flags,
-				  struct pt_regs *regs);
+extern vm_fault_t do_handle_mm_fault(struct vm_area_struct *vma,
+		unsigned long address, unsigned int flags,
+		unsigned long seq, struct pt_regs *regs);
+static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
+		unsigned long address, unsigned int flags,
+		struct pt_regs *regs)
+{
+	return do_handle_mm_fault(vma, address, flags, 0, regs);
+}
 extern int fixup_user_fault(struct mm_struct *mm,
 			    unsigned long address, unsigned int fault_flags,
 			    bool *unlocked);
diff --git a/mm/memory.c b/mm/memory.c
index f83e06b1dafb..aa24cd8c06e9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4761,11 +4761,15 @@ static inline void mm_account_fault(struct pt_regs *regs,
  * The mmap_lock may have been released depending on flags and our
  * return value.  See filemap_fault() and __folio_lock_or_retry().
  */
-vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
-			   unsigned int flags, struct pt_regs *regs)
+vm_fault_t do_handle_mm_fault(struct vm_area_struct *vma,
+		unsigned long address, unsigned int flags,
+		unsigned long seq, struct pt_regs *regs)
 {
 	vm_fault_t ret;
 
+	if (flags & FAULT_FLAG_SPECULATIVE)
+		return VM_FAULT_RETRY;
+
 	__set_current_state(TASK_RUNNING);
 
 	count_vm_event(PGFAULT);
@@ -4807,7 +4811,7 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 
 	return ret;
 }
-EXPORT_SYMBOL_GPL(handle_mm_fault);
+EXPORT_SYMBOL_GPL(do_handle_mm_fault);
 
 #ifndef __PAGETABLE_P4D_FOLDED
 /*
-- 
2.20.1