Date: Sun, 17 May 98 03:38:48 +0100 (BST) From: iedowse@maths.tcd.ie To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: bin/6658: -stable getcwd(3) performs unnecessary lstats Message-ID: <9805170338.aa14317@walton.maths.tcd.ie>
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>Number: 6658
>Category: bin
>Synopsis: -stable getcwd(3) performs unnecessary lstats
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Sat May 16 19:40:03 PDT 1998
>Last-Modified:
>Originator: Ian Dowse
>Organization:
School of Mathematics,
Trinity College Dublin
>Release: FreeBSD 2.2.6-STABLE i386
>Environment:
FreeBSD 2.2.6-STABLE
>Description:
getcwd(3) in -stable does a lot of lstat'ing every time it crosses
a mount point. This can really slow down its operation if it has
to lstat nfs disks or slow devices. The usual suggested workaround
of putting all 'slow' filesystems in separate directories is not
ideal.
The path component that getcwd does all these lstats to find can
virtually always be obtained using statfs(2) at a much lower cost.
The patch below makes getcwd first try statfs, and then resort to
the old method if this fails (I'm not convinced that statfs will
get the correct answer in absolutely every situation).
This PR can of course be ignored if a getcwd syscall is likely to
appear soon in -stable.
>How-To-Repeat:
Run sh with cwd in filesystem /f1 while nfs filesystem /f2 is not
responding.
>Fix:
*** /usr/src/lib/libc/gen/getcwd.c Thu Mar 26 09:22:48 1998
--- getcwd.c Sun May 17 03:30:24 1998
***************
*** 36,41 ****
--- 36,42 ----
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
+ #include <sys/mount.h>
#include <sys/stat.h>
#include <errno.h>
***************
*** 169,175 ****
if (dp->d_fileno == ino)
break;
}
! } else
for (;;) {
if (!(dp = readdir(dir)))
goto notfound;
--- 170,193 ----
if (dp->d_fileno == ino)
break;
}
! } else {
! struct statfs sfs;
! char *dirname;
!
! if (!statfs(".", &sfs) &&
! (dirname = rindex(sfs.f_mntonname, '/')))
! while((dp = readdir(dir))) {
! if (ISDOT(dp))
! continue;
! bcopy(dp->d_name, bup, dp->d_namlen+1);
! if (!strcmp(dirname + 1, dp->d_name) &&
! !lstat(up, &s) &&
! s.st_dev == dev &&
! s.st_ino == ino)
! goto found;
! }
! rewinddir(dir);
!
for (;;) {
if (!(dp = readdir(dir)))
goto notfound;
***************
*** 187,193 ****
--- 205,213 ----
if (s.st_dev == dev && s.st_ino == ino)
break;
}
+ }
+ found:
/*
* Check for length of the current name, preceding slash,
* leading slash.
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