From: James H Date: Tue, 26 Jul 2011 10:47:20 +0000 (+0100) Subject: Call exportfs -v once for NFS shares. X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=commitdiff_plain;h=5333eb0b3b18d345052b8cfaf41b90a0c5781fb8;p=zfs.git Call exportfs -v once for NFS shares. At the moment we call exportfs -v every time we check whether an NFS share is active. This happens every time you run a zfs or zpool command, making them extremely slow when you have a lot of exports. The time taken is approx O(n2) of the number of shares. This commit stores the output from exportfs -v in a temporary file and use this to speed up subsequent accesses. This mechanism is still too slow - if you have tens of thousands of NFS shares it will still be painful running ANY zfs/zpool command. Signed-off-by: Gunnar Beutner Signed-off-by: Brian Behlendorf Closes #341 --- diff --git a/lib/libshare/nfs.c b/lib/libshare/nfs.c index 60edaa2..4d13014 100644 --- a/lib/libshare/nfs.c +++ b/lib/libshare/nfs.c @@ -36,6 +36,12 @@ static sa_fstype_t *nfs_fstype; static boolean_t nfs_available; +/* + * nfs_exportfs_temp_fd refers to a temporary copy of the output + * from exportfs -v. + */ +static int nfs_exportfs_temp_fd = -1; + typedef int (*nfs_shareopt_callback_t)(const char *opt, const char *value, void *cookie); @@ -493,111 +499,62 @@ nfs_validate_shareopts(const char *shareopts) return SA_OK; } -/* - * TODO: Rather than invoking "exportfs -v" once for each share we should only - * call it once for all shares. - */ static boolean_t is_share_active(sa_share_impl_t impl_share) { - pid_t pid; - int rc, status; - int pipes[2]; - FILE *exportfs_stdout; char line[512]; char *tab, *cur; - boolean_t share_active = B_FALSE; + FILE *nfs_exportfs_temp_fp; - if (pipe(pipes) < 0) + if (nfs_exportfs_temp_fd < 0) return B_FALSE; - pid = fork(); + nfs_exportfs_temp_fp = fdopen(dup(nfs_exportfs_temp_fd), "r"); - if (pid < 0) + if (nfs_exportfs_temp_fp == NULL || + fseek(nfs_exportfs_temp_fp, 0, SEEK_SET) < 0) { + fclose(nfs_exportfs_temp_fp); return B_FALSE; + } - if (pid > 0) { - share_active = B_FALSE; - - exportfs_stdout = fdopen(pipes[0], "r"); - close(pipes[1]); + while (fgets(line, sizeof(line), nfs_exportfs_temp_fp) != NULL) { + /* + * exportfs uses separate lines for the share path + * and the export options when the share path is longer + * than a certain amount of characters; this ignores + * the option lines + */ + if (line[0] == '\t') + continue; - while (fgets(line, sizeof(line), exportfs_stdout) != NULL) { - if (share_active) - continue; + tab = strchr(line, '\t'); + if (tab != NULL) { + *tab = '\0'; + cur = tab - 1; + } else { /* - * exportfs uses separate lines for the share path - * and the export options when the share path is longer - * than a certain amount of characters; this ignores - * the option lines + * there's no tab character, which means the + * NFS options are on a separate line; we just + * need to remove the new-line character + * at the end of the line */ - if (line[0] == '\t') - continue; - - tab = strchr(line, '\t'); - - if (tab != NULL) { - *tab = '\0'; - cur = tab - 1; - } else { - /* - * there's no tab character, which means the - * NFS options are on a separate line; we just - * need to remove the new-line character - * at the end of the line - */ - cur = line + strlen(line) - 1; - } - - /* remove trailing spaces and new-line characters */ - while (cur >= line && - (*cur == ' ' || *cur == '\n')) - *cur-- = '\0'; - - if (strcmp(line, impl_share->sharepath) == 0) { - share_active = B_TRUE; - - /* - * We can't break here just yet, otherwise - * exportfs might die due to write() failing - * with EPIPE once we've closed the pipe file - * descriptor - we need to read until EOF - * occurs on the stdout pipe. - */ - } + cur = line + strlen(line) - 1; } - fclose(exportfs_stdout); + /* remove trailing spaces and new-line characters */ + while (cur >= line && (*cur == ' ' || *cur == '\n')) + *cur-- = '\0'; - while ((rc = waitpid(pid, &status, 0)) <= 0 && errno == EINTR) - ; /* empty loop body */ - - if (rc <= 0) - return B_FALSE; - - if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) - return B_FALSE; - - return share_active; + if (strcmp(line, impl_share->sharepath) == 0) { + fclose(nfs_exportfs_temp_fp); + return B_TRUE; + } } - /* child */ - - /* exportfs -v */ - - close(pipes[0]); - - if (dup2(pipes[1], STDOUT_FILENO) < 0) - exit(1); - - rc = execlp("/usr/sbin/exportfs", "exportfs", "-v", NULL); - - if (rc < 0) { - exit(1); - } + fclose(nfs_exportfs_temp_fp); - exit(0); + return B_FALSE; } static int @@ -654,11 +611,40 @@ static const sa_share_ops_t nfs_shareops = { .clear_shareopts = nfs_clear_shareopts, }; +/* + * nfs_check_exportfs() checks that the exportfs command runs + * and also maintains a temporary copy of the output from + * exportfs -v. + * To update this temporary copy simply call this function again. + * + * TODO : Use /var/lib/nfs/etab instead of our private copy. + * But must implement locking to prevent concurrent access. + * + * TODO : The temporary file descriptor is never closed since + * there is no libshare_nfs_fini() function. + */ static int nfs_check_exportfs(void) { pid_t pid; - int rc, status, null_fd; + int rc, status; + static char nfs_exportfs_tempfile[] = "/tmp/exportfs.XXXXXX"; + + /* + * Close any existing temporary copies of output from exportfs. + * We have already called unlink() so file will be deleted. + */ + if (nfs_exportfs_temp_fd >= 0) + close(nfs_exportfs_temp_fd); + + nfs_exportfs_temp_fd = mkstemp(nfs_exportfs_tempfile); + + if (nfs_exportfs_temp_fd < 0) + return SA_SYSTEM_ERR; + + unlink(nfs_exportfs_tempfile); + + fcntl(nfs_exportfs_temp_fd, F_SETFD, FD_CLOEXEC); pid = fork(); @@ -680,14 +666,12 @@ nfs_check_exportfs(void) /* child */ - null_fd = open("/dev/null", O_RDONLY); + /* exportfs -v */ - if (null_fd < 0 || dup2(null_fd, 1) < 0 || dup2(null_fd, 2) < 0) + if (dup2(nfs_exportfs_temp_fd, STDOUT_FILENO) < 0) exit(1); - close(null_fd); - - rc = execlp("/usr/sbin/exportfs", "exportfs", NULL); + rc = execlp("/usr/sbin/exportfs", "exportfs", "-v", NULL); if (rc < 0) { exit(1);