[RHEL8,COMMIT] mm: introduce FAULT_FLAG_INTERRUPTIBLE

Submitted by Konstantin Khorenko on April 20, 2020, 7:34 a.m.

Details

Message ID 202004200734.03K7YK2f016014@finist_co8.work.ct
State New
Series "Series without cover letter"
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Commit Message

Konstantin Khorenko April 20, 2020, 7:34 a.m.
The commit is pushed to "branch-rh8-4.18.0-80.1.2.vz8.3.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-80.1.2.vz8.3.6
------>
commit 8fc57248b43caed9c2db6d64ce54780ba8c1c046
Author: Peter Xu <peterx@redhat.com>
Date:   Mon Apr 20 10:34:19 2020 +0300

    mm: introduce FAULT_FLAG_INTERRUPTIBLE
    
    handle_userfaultfd() is currently the only one place in the kernel page
    fault procedures that can respond to non-fatal userspace signals.  It was
    trying to detect such an allowance by checking against USER & KILLABLE
    flags, which was "un-official".
    
    In this patch, we introduced a new flag (FAULT_FLAG_INTERRUPTIBLE) to show
    that the fault handler allows the fault procedure to respond even to
    non-fatal signals.  Meanwhile, add this new flag to the default fault
    flags so that all the page fault handlers can benefit from the new flag.
    With that, replacing the userfault check to this one.
    
    Since the line is getting even longer, clean up the fault flags a bit too
    to ease TTY users.
    
    Although we've got a new flag and applied it, we shouldn't have any
    functional change with this patch so far.
    
    Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Peter Xu <peterx@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Tested-by: Brian Geffon <bgeffon@google.com>
    Reviewed-by: David Hildenbrand <david@redhat.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Bobby Powers <bobbypowers@gmail.com>
    Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
    Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Jerome Glisse <jglisse@redhat.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
    Cc: Martin Cracauer <cracauer@cons.org>
    Cc: Marty McFadden <mcfadden8@llnl.gov>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Maya Gokhale <gokhale2@llnl.gov>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Mike Kravetz <mike.kravetz@oracle.com>
    Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
    Cc: Pavel Emelyanov <xemul@openvz.org>
    Link: http://lkml.kernel.org/r/20200220195348.16302-1-peterx@redhat.com
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    
    https://jira.sw.ru/browse/PSBM-102938
    (cherry picked from commit c270a7eedcf278304e05ebd2c96807487c97db61)
    Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 fs/userfaultfd.c   |  4 +---
 include/linux/mm.h | 39 ++++++++++++++++++++++++++++-----------
 2 files changed, 29 insertions(+), 14 deletions(-)

Patch hide | download patch | download mbox

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 905bad9139bb..ebabf5983830 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -455,9 +455,7 @@  int handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	uwq.ctx = ctx;
 	uwq.waken = false;
 
-	return_to_userland =
-		(vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) ==
-		(FAULT_FLAG_USER|FAULT_FLAG_KILLABLE);
+	return_to_userland = vmf->flags & FAULT_FLAG_INTERRUPTIBLE;
 	blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
 			 TASK_KILLABLE;
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 060408343ac6..927059b8d679 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -312,22 +312,38 @@  extern unsigned int kobjsize(const void *objp);
  */
 extern pgprot_t protection_map[16];
 
-#define FAULT_FLAG_WRITE	0x01	/* Fault was a write access */
-#define FAULT_FLAG_MKWRITE	0x02	/* Fault was mkwrite of existing pte */
-#define FAULT_FLAG_ALLOW_RETRY	0x04	/* Retry fault if blocking */
-#define FAULT_FLAG_RETRY_NOWAIT	0x08	/* Don't drop mmap_sem and wait when retrying */
-#define FAULT_FLAG_KILLABLE	0x10	/* The fault task is in SIGKILL killable region */
-#define FAULT_FLAG_TRIED	0x20	/* Second try */
-#define FAULT_FLAG_USER		0x40	/* The fault originated in userspace */
-#define FAULT_FLAG_REMOTE	0x80	/* faulting for non current tsk/mm */
-#define FAULT_FLAG_INSTRUCTION  0x100	/* The fault was during an instruction fetch */
+/**
+ * Fault flag definitions.
+ *
+ * @FAULT_FLAG_WRITE: Fault was a write fault.
+ * @FAULT_FLAG_MKWRITE: Fault was mkwrite of existing PTE.
+ * @FAULT_FLAG_ALLOW_RETRY: Allow to retry the fault if blocked.
+ * @FAULT_FLAG_RETRY_NOWAIT: Don't drop mmap_sem and wait when retrying.
+ * @FAULT_FLAG_KILLABLE: The fault task is in SIGKILL killable region.
+ * @FAULT_FLAG_TRIED: The fault has been tried once.
+ * @FAULT_FLAG_USER: The fault originated in userspace.
+ * @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
+ * @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
+ * @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
+ */
+#define FAULT_FLAG_WRITE			0x01
+#define FAULT_FLAG_MKWRITE			0x02
+#define FAULT_FLAG_ALLOW_RETRY			0x04
+#define FAULT_FLAG_RETRY_NOWAIT			0x08
+#define FAULT_FLAG_KILLABLE			0x10
+#define FAULT_FLAG_TRIED			0x20
+#define FAULT_FLAG_USER				0x40
+#define FAULT_FLAG_REMOTE			0x80
+#define FAULT_FLAG_INSTRUCTION  		0x100
+#define FAULT_FLAG_INTERRUPTIBLE		0x200
 
 /*
  * The default fault flags that should be used by most of the
  * arch-specific page fault handlers.
  */
 #define FAULT_FLAG_DEFAULT  (FAULT_FLAG_ALLOW_RETRY | \
-			     FAULT_FLAG_KILLABLE)
+			     FAULT_FLAG_KILLABLE | \
+			     FAULT_FLAG_INTERRUPTIBLE)
 
 #define FAULT_FLAG_TRACE \
 	{ FAULT_FLAG_WRITE,		"WRITE" }, \
@@ -338,7 +354,8 @@  extern pgprot_t protection_map[16];
 	{ FAULT_FLAG_TRIED,		"TRIED" }, \
 	{ FAULT_FLAG_USER,		"USER" }, \
 	{ FAULT_FLAG_REMOTE,		"REMOTE" }, \
-	{ FAULT_FLAG_INSTRUCTION,	"INSTRUCTION" }
+	{ FAULT_FLAG_INSTRUCTION,	"INSTRUCTION" }, \
+	{ FAULT_FLAG_INTERRUPTIBLE,	"INTERRUPTIBLE" }
 
 /*
  * vm_fault is filled by the the pagefault handler and passed to the vma's