Messages in this thread Patch in this message | | | Subject | [PATCH] fs: avoid unecessary smp_wmb() in dup_fd() | From | Eric Dumazet <> | Date | Sat, 07 May 2011 08:30:01 +0200 |
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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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