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Groups > linux.kernel > #1660000

[RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject [RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage
Date 2017-06-07 18:30 +0200
Message-ID <tPM0j-zo-39@gated-at.bofh.it> (permalink)
References <tPM0i-zo-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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While we could replace the smp_mb__before_spinlock() with the new
smp_mb__after_spinlock(), the normal pattern is to use
smp_store_release() to publish an object that is used for
lockless_dereference() -- and mirrors the regular rcu_assign_pointer()
/ rcu_dereference() patterns.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 fs/overlayfs/readdir.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -446,14 +446,14 @@ static int ovl_dir_fsync(struct file *fi
 
 			ovl_path_upper(dentry, &upperpath);
 			realfile = ovl_path_open(&upperpath, O_RDONLY);
-			smp_mb__before_spinlock();
+
 			inode_lock(inode);
 			if (!od->upperfile) {
 				if (IS_ERR(realfile)) {
 					inode_unlock(inode);
 					return PTR_ERR(realfile);
 				}
-				od->upperfile = realfile;
+				smp_store_release(&od->upperfile, realfile);
 			} else {
 				/* somebody has beaten us to it */
 				if (!IS_ERR(realfile))

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Thread

[RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 2/5] locking: Introduce smp_mb__after_spinlock(). Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
    Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Will Deacon <will.deacon@arm.com> - 2017-06-09 16:50 +0200
      Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Peter Zijlstra <peterz@infradead.org> - 2017-06-09 20:50 +0200
  [RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 4/5] locking: Remove smp_mb__before_spinlock() Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
    Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 02:40 +0200
      Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 09:00 +0200
        Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 09:40 +0200
          Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 10:00 +0200
            Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 10:30 +0200
            Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Michael Ellerman <mpe@ellerman.id.au> - 2017-06-08 12:00 +0200
              Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 12:10 +0200
                Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 14:50 +0200
                Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 15:20 +0200
                Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 15:50 +0200
  Re: [RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Will Deacon <will.deacon@arm.com> - 2017-06-09 17:00 +0200

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