diff options
Diffstat (limited to 'support/export/xtab.c')
| -rw-r--r-- | support/export/xtab.c | 47 |
1 files changed, 46 insertions, 1 deletions
diff --git a/support/export/xtab.c b/support/export/xtab.c index 3ef3661..d9265a2 100644 --- a/support/export/xtab.c +++ b/support/export/xtab.c @@ -18,6 +18,8 @@ #include "xio.h" #include "xlog.h" +static void cond_rename(char *newfile, char *oldfile); + static int xtab_read(char *xtab, int is_export) { @@ -104,7 +106,7 @@ xtab_write(char *xtab, char *xtabtmp, int is_export) } endexportent(); - rename(xtabtmp, xtab); + cond_rename(xtabtmp, xtab); xfunlock(lockid); @@ -142,3 +144,46 @@ xtab_append(nfs_export *exp) exp->m_xtabent = 1; } +/* + * rename newfile onto oldfile unless + * they are identical + */ +static void cond_rename(char *newfile, char *oldfile) +{ + int nfd, ofd; + char nbuf[4096], obuf[4096]; + int ncnt, ocnt; + + nfd = open(newfile, 0); + if (nfd < 0) + return; + ofd = open(oldfile, 0); + if (ofd < 0) { + close(nfd); + rename(newfile, oldfile); + return; + } + + do { + ncnt = read(nfd, nbuf, sizeof(nbuf)); + if (ncnt < 0) + break; + ocnt = read(ofd, obuf, sizeof(obuf)); + if (ocnt < 0) + break; + if (ncnt != ocnt) + break; + if (ncnt == 0) { + close(nfd); + close(ofd); + unlink(newfile); + return; + } + } while (memcmp(obuf, nbuf, ncnt) == 0); + + /* some mis-match */ + close(nfd); + close(ofd); + rename(newfile, oldfile); + return; +} |