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Subject[PATCH] fs: avoid unecessary smp_wmb() in dup_fd()
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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@gmail.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: linux-fsdevel@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Changli Gao <xiaosuo@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
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);




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