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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 <gunnar@beutner.name>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #341
This commit is contained in:
James H 2011-07-26 11:47:20 +01:00 committed by Brian Behlendorf
parent 77999e804f
commit 5333eb0b3b
1 changed files with 74 additions and 90 deletions
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118
lib/libshare/nfs.c
View File

@ -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);
@ -493,39 +499,25 @@ 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), exportfs_stdout) != NULL) {
if (share_active)
continue;
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
@ -551,53 +543,18 @@ is_share_active(sa_share_impl_t impl_share)
}
/* remove trailing spaces and new-line characters */
while (cur >= line &&
(*cur == ' ' || *cur == '\n'))
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.
*/
fclose(nfs_exportfs_temp_fp);
return B_TRUE;
}
}
fclose(exportfs_stdout);
fclose(nfs_exportfs_temp_fp);
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;
}
/* 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);
}
exit(0);
}
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);