Author: kib
Date: Sun Jan 1 23:51:18 2012
New Revision: 229248
URL: http://svn.freebsd.org/changeset/base/229248
Log:
MFC r228306:
Most users of pipe(2) do not call fstat(2) on the returned pipe descriptors.
Optimize for the case, by lazily allocating the pipe inode number at the
fstat(2) time.
Modified:
stable/9/sys/kern/sys_pipe.c
Directory Properties:
stable/9/sys/ (props changed)
Modified: stable/9/sys/kern/sys_pipe.c
==============================================================================
--- stable/9/sys/kern/sys_pipe.c Sun Jan 1 23:49:11 2012
(r229247)
+++ stable/9/sys/kern/sys_pipe.c Sun Jan 1 23:51:18 2012
(r229248)
@@ -569,12 +569,7 @@ pipe_create(pipe, backing)
/* If we're not backing this pipe, no need to do anything. */
error = 0;
}
- if (error == 0) {
- pipe->pipe_ino = alloc_unr(pipeino_unr);
- if (pipe->pipe_ino == -1)
- /* pipeclose will clear allocated kva */
- error = ENOMEM;
- }
+ pipe->pipe_ino = -1;
return (error);
}
@@ -1398,16 +1393,40 @@ pipe_stat(fp, ub, active_cred, td)
struct ucred *active_cred;
struct thread *td;
{
- struct pipe *pipe = fp->f_data;
+ struct pipe *pipe;
+ int new_unr;
#ifdef MAC
int error;
+#endif
+ pipe = fp->f_data;
PIPE_LOCK(pipe);
+#ifdef MAC
error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
- PIPE_UNLOCK(pipe);
- if (error)
+ if (error) {
+ PIPE_UNLOCK(pipe);
return (error);
+ }
#endif
+ /*
+ * Lazily allocate an inode number for the pipe. Most pipe
+ * users do not call fstat(2) on the pipe, which means that
+ * postponing the inode allocation until it is must be
+ * returned to userland is useful. If alloc_unr failed,
+ * assign st_ino zero instead of returning an error.
+ * Special pipe_ino values:
+ * -1 - not yet initialized;
+ * 0 - alloc_unr failed, return 0 as st_ino forever.
+ */
+ if (pipe->pipe_ino == (ino_t)-1) {
+ new_unr = alloc_unr(pipeino_unr);
+ if (new_unr != -1)
+ pipe->pipe_ino = new_unr;
+ else
+ pipe->pipe_ino = 0;
+ }
+ PIPE_UNLOCK(pipe);
+
bzero(ub, sizeof(*ub));
ub->st_mode = S_IFIFO;
ub->st_blksize = PAGE_SIZE;
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