Commit eb095c14 authored Mar 06, 2020 by Zhouyi Zhou Committed by Trond Myklebust Mar 16, 2020

NFS:remove redundant call to nfs_do_access



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@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

parent 68e9a246

fs/nfs/dir.c

+1 −8

Original line number	Diff line number	Diff line
		@@ -2759,14 +2759,7 @@ force_lookup:
		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);
		}
		out:
		if (!res && (mask & MAY_EXEC))
		res = nfs_execute_ok(inode, mask);

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