libf2fs: increase robustness when called on root device

On some systems '/proc/mounts' contains the entry '/dev/root'
as alias for the root device, while that alias doesn't actually
exist as symlink in /dev.

/proc/mounts:
/dev/root / f2fs rw,noatime,background_gc=on,user_xattr,acl,inline_data,extent_cache,active_logs=6 0 0

mount:
/dev/mmcblk1p1 on / type f2fs (rw,noatime,background_gc=on,user_xattr,acl,inline_data,extent_cache,active_logs=6)

If the root device is mounted RO, and we try to scan it, via
'fsck.f2fs /dev/mmcblk1p1', then fsck.f2fs exits because it can't
find the entry in /proc/mounts.

Try harder to identify the root device of the system first, and
in case we are operating on it, check also for '/dev/root' in mounts.

Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
index 19ce250..bfe9b3f 100644 (file)
--- a/include/f2fs_fs.h
+++ b/include/f2fs_fs.h
@@ -279,6 +279,7 @@ struct f2fs_configuration {
        int32_t dump_fd;
        char *device_name;
        char *extension_list;
+       const char *rootdev_name;
        int dbg_lv;
        int trim;
        int func;

diff --git a/lib/libf2fs.c b/lib/libf2fs.c
index 2284a78..6140452 100644 (file)
--- a/lib/libf2fs.c
+++ b/lib/libf2fs.c
@@ -21,6 +21,7 @@
 #include <sys/ioctl.h>
 #include <scsi/sg.h>
 #include <linux/hdreg.h>
+#include <linux/limits.h>
 
 #include <f2fs_fs.h>
 
@@ -485,6 +486,53 @@ int f2fs_crc_valid(u_int32_t blk_crc, void *buf, int len)
 }
 
 /*
+ * try to identify the root device
+ */
+const char *get_rootdev()
+{
+       struct stat sb;
+       int fd, ret;
+       char buf[32];
+       char *uevent, *ptr;
+
+       static char rootdev[PATH_MAX + 1];
+
+       if (stat("/", &sb) == -1)
+               return NULL;
+
+       snprintf(buf, 32, "/sys/dev/block/%u:%u/uevent",
+               major(sb.st_dev), minor(sb.st_dev));
+
+       fd = open(buf, O_RDONLY);
+
+       if (fd < 0)
+               return NULL;
+
+       ret = lseek(fd, (off_t)0, SEEK_END);
+       (void)lseek(fd, (off_t)0, SEEK_SET);
+
+       if (ret == -1) {
+               close(fd);
+               return NULL;
+       }
+
+       uevent = malloc(ret + 1);
+       uevent[ret] = '\0';
+
+       ret = read(fd, uevent, ret);
+       close(fd);
+
+       ptr = strstr(uevent, "DEVNAME");
+       if (!ptr)
+               return NULL;
+
+       ret = sscanf(ptr, "DEVNAME=%s\n", buf);
+       snprintf(rootdev, PATH_MAX + 1, "/dev/%s", buf);
+
+       return rootdev;
+}
+
+/*
  * device information
  */
 void f2fs_init_configuration(void)
@@ -493,6 +541,7 @@ void f2fs_init_configuration(void)
        c.sector_size = DEFAULT_SECTOR_SIZE;
        c.sectors_per_blk = DEFAULT_SECTORS_PER_BLOCK;
        c.blks_per_seg = DEFAULT_BLOCKS_PER_SEGMENT;
+       c.rootdev_name = get_rootdev();
 
        /* calculated by overprovision ratio */
        c.reserved_segments = 0;
@@ -532,8 +581,12 @@ static int is_mounted(const char *mpt, const char *device)
 int f2fs_dev_is_umounted(void)
 {
        struct stat st_buf;
+       int is_rootdev = 0;
        int ret = 0;
 
+       if (c.rootdev_name && !strcmp(c.device_name, c.rootdev_name))
+               is_rootdev = 1;
+
        /*
         * try with /proc/mounts fist to detect RDONLY.
         * f2fs_stop_checkpoint makes RO in /proc/mounts while RW in /etc/mtab.
@@ -551,6 +604,19 @@ int f2fs_dev_is_umounted(void)
        }
 
        /*
+        * If we are supposed to operate on the root device, then
+        * also check the mounts for '/dev/root', which sometimes
+        * functions as an alias for the root device.
+        */
+       if (is_rootdev) {
+               ret = is_mounted("/proc/mounts", "/dev/root");
+               if (ret) {
+                       MSG(0, "Info: Mounted device!\n");
+                       return -1;
+               }
+       }
+
+       /*
         * If f2fs is umounted with -l, the process can still use
         * the file system. In this case, we should not format.
         */