[PATCH] fs: avoid unecessary smp_wmb() in dup_fd()

[Eric Dumazet]

While copying old_fds array to new_fds, we dont need
rcu_assign_pointer() and its smp_wmb(), since we are the only thread
populating new_fds at this point.

A bit later, rcu_assign_pointer(newf->fdt, new_fdt) makes sure
our writes are committed to memory before new_fds content is visible to
other threads.

This removes following sparse warning :

fs/file.c:371:3: warning: incorrect type in assignment (different
address spaces)
fs/file.c:371:3:    expected struct file *<noident>
fs/file.c:371:3:    got struct file [noderef] <asn:4>*<noident>

Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Matthew Wilcox <matthew@xxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Changli Gao <xiaosuo@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
 fs/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/file.c b/fs/file.c
index 4c6992d..8320a8e 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -368,7 +368,7 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 			 */
 			FD_CLR(open_files - i, new_fdt->open_fds);
 		}
-		rcu_assign_pointer(*new_fds++, f);
+		*new_fds++ = f;
 	}
 	spin_unlock(&oldf->file_lock);
 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/