ping
On 3/6/20, Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> wrote:
> In function nfs_permission:
> 1. the rcu_read_lock and rcu_read_unlock around nfs_do_access
> is unnecessary because the rcu critical data structure is already
> protected in subsidiary function nfs_access_get_cached_rcu. No other
> data structure needs rcu_read_lock in nfs_do_access.
>
> 2. call nfs_do_access once is enough, because:
> 2-1. when mask has MAY_NOT_BLOCK bit
> The second call to nfs_do_access will not happen.
>
> 2-2. when mask has no MAY_NOT_BLOCK bit
> The second call to nfs_do_access will happen if res == -ECHILD, which
> means the first nfs_do_access goes out after statement if (!may_block).
> The second call to nfs_do_access will go through this procedure once
> again except continue the work after if (!may_block).
> But above work can be performed by only one call to nfs_do_access
> without mangling the mask flag.
>
> Tested in x86_64
> Signed-off-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
> ---
> fs/nfs/dir.c | 9 +--------
> 1 files changed, 1 insertions(+), 8 deletions(-)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 193d6fb..37b0c10 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -2732,14 +2732,7 @@ int nfs_permission(struct inode *inode, int mask)
> if (!NFS_PROTO(inode)->access)
> goto out_notsup;
>
> - /* Always try fast lookups first */
> - rcu_read_lock();
> - res = nfs_do_access(inode, cred, mask|MAY_NOT_BLOCK);
> - rcu_read_unlock();
> - if (res == -ECHILD && !(mask & MAY_NOT_BLOCK)) {
> - /* Fast lookup failed, try the slow way */
> - res = nfs_do_access(inode, cred, mask);
> - }
> + res = nfs_do_access(inode, cred, mask);
> out:
> if (!res && (mask & MAY_EXEC))
> res = nfs_execute_ok(inode, mask);
> --
> 1.7.1
>
>
