ee416b3fe3
- gfs2_grow: Don't try to open an empty string - libgfs2: Add lgfs2 open mnt functions - Switch is pathname mounted callers to lgfs2 open mnt - libgfs2 Remove is pathname mounted Resolves: bz#1079286
142 lines
4.3 KiB
Diff
142 lines
4.3 KiB
Diff
commit 25c6e51bb4d083eb341bbc8541bb2ad278988f10
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Author: Andrew Price <anprice@redhat.com>
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Date: Sat Nov 16 02:10:52 2013 -0600
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libgfs2: Add lgfs2_open_mnt* functions
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lgfs2_open_mnt is a replacement for is_pathname_mounted which tries to reduce
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races by opening paths speculatively and passing back the open fds once they're
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known to be correct. lgfs2_open_mnt_{dev,dir} build on this to provide a
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convenient way to open just the device or mount directory relating to a path
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which could be either.
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Signed-off-by: Andrew Price <anprice@redhat.com>
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diff --git a/gfs2/libgfs2/libgfs2.h b/gfs2/libgfs2/libgfs2.h
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index f864a08..3e5d09c 100644
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--- a/gfs2/libgfs2/libgfs2.h
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+++ b/gfs2/libgfs2/libgfs2.h
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@@ -12,6 +12,7 @@
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#include <linux/limits.h>
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#include <endian.h>
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#include <byteswap.h>
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+#include <mntent.h>
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#include <linux/gfs2_ondisk.h>
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#include "osi_list.h"
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@@ -715,6 +716,9 @@ extern int compute_heightsize(struct gfs2_sbd *sdp, uint64_t *heightsize,
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uint32_t *maxheight, uint32_t bsize1, int diptrs, int inptrs);
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extern int compute_constants(struct gfs2_sbd *sdp);
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extern int is_pathname_mounted(char *path_name, char *device_name, int *ro_mount);
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+extern int lgfs2_open_mnt(const char *path, int dirflags, int *dirfd, int devflags, int *devfd, struct mntent **mnt);
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+extern int lgfs2_open_mnt_dev(const char *path, int flags, struct mntent **mnt);
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+extern int lgfs2_open_mnt_dir(const char *path, int flags, struct mntent **mnt);
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extern int find_gfs2_meta(struct gfs2_sbd *sdp);
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extern int dir_exists(const char *dir);
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extern int mount_gfs2_meta(struct gfs2_sbd *sdp);
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diff --git a/gfs2/libgfs2/misc.c b/gfs2/libgfs2/misc.c
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index 7f500e6..195b983 100644
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--- a/gfs2/libgfs2/misc.c
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+++ b/gfs2/libgfs2/misc.c
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@@ -163,6 +163,100 @@ int is_pathname_mounted(char *path_name, char *device_name, int *ro_mount)
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return 1; /* mounted */
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}
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+/* Returns 0 if fd1 and fd2 refer to the same device/file, 1 otherwise, or -1 on error */
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+static int fdcmp(int fd1, int fd2)
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+{
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+ struct stat st1, st2;
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+ if ((fstat(fd1, &st1) != 0) || (fstat(fd2, &st2) != 0))
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+ return -1;
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+ if (S_ISBLK(st1.st_mode) && S_ISBLK(st2.st_mode)) {
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+ if (st1.st_rdev == st2.st_rdev) {
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+ return 0;
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+ }
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+ } else if ((st1.st_dev == st2.st_dev) && (st1.st_ino == st2.st_ino)) {
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+ return 0;
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+ }
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+ return 1;
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+}
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+
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+int lgfs2_open_mnt(const char *path, int dirflags, int *dirfd, int devflags, int *devfd, struct mntent **mnt)
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+{
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+ FILE *fp = setmntent("/proc/mounts", "r");
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+ if (fp == NULL) {
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+ perror("open: /proc/mounts");
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+ return 1;
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+ }
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+ /* Assume path is mount point until we know better. */
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+ *dirfd = open(path, dirflags);
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+ if (*dirfd < 0)
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+ return 1;
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+
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+ while ((*mnt = getmntent(fp)) != NULL) {
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+ int fd;
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+ if (strcmp((*mnt)->mnt_type, "gfs2") != 0)
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+ continue;
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+ *devfd = open((*mnt)->mnt_fsname, devflags);
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+ /* Defer checking *devfd until later: whether it's ok to ignore
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+ * the error depends on whether we find the mount point. */
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+
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+ if (strcmp(path, (*mnt)->mnt_dir) == 0)
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+ break;
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+ if (strcmp(path, (*mnt)->mnt_fsname) == 0 || fdcmp(*dirfd, *devfd) == 0) {
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+ /* We have a match but our above assumption was
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+ incorrect and *dirfd is actually the device. */
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+ close(*dirfd);
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+ *dirfd = open((*mnt)->mnt_dir, dirflags);
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+ break;
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+ }
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+
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+ fd = open((*mnt)->mnt_dir, dirflags);
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+ if (fd >= 0) {
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+ int diff = fdcmp(*dirfd, fd);
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+ close(fd);
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+ if (diff == 0)
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+ break;
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+ }
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+ if (*devfd >= 0)
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+ close(*devfd);
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+ }
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+ endmntent(fp);
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+ if (*mnt == NULL) {
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+ close(*dirfd);
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+ return 0; /* Success. Answer is no. Both fds closed. */
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+ }
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+ if (*dirfd < 0) {
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+ close(*devfd);
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+ return 1;
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+ }
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+ if (*devfd < 0) {
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+ close(*dirfd);
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+ return 1;
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+ }
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+ return 0; /* Success. Answer is yes. Both fds open. */
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+}
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+
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+int lgfs2_open_mnt_dev(const char *path, int flags, struct mntent **mnt)
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+{
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+ int dirfd = -1;
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+ int devfd = -1;
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+ if (lgfs2_open_mnt(path, O_RDONLY, &dirfd, flags, &devfd, mnt) != 0)
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+ return -1;
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+ if (*mnt != NULL)
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+ close(dirfd);
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+ return devfd;
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+}
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+
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+int lgfs2_open_mnt_dir(const char *path, int flags, struct mntent **mnt)
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+{
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+ int dirfd = -1;
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+ int devfd = -1;
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+ if (lgfs2_open_mnt(path, flags, &dirfd, O_RDONLY, &devfd, mnt) != 0)
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+ return -1;
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+ if (*mnt != NULL)
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+ close(devfd);
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+ return dirfd;
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+}
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+
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static int lock_for_admin(struct gfs2_sbd *sdp)
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{
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int error;
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