On 2/11/13 7:25 PM, Tsutomu Itoh wrote:
> Currently, the following commands succeed.
>
> # cat /proc/swaps
> Filename Type Size Used
> Priority
> /dev/sda3 partition 8388604 0 -1
> /dev/sdc8 partition 9765884 0 -2
> # mkfs.btrfs /dev/sdc8
>
> WARNING! - Btrfs v0.20-rc1-165-g82ac345 IS EXPERIMENTAL
> WARNING! - see http://btrfs.wiki.kernel.org before using
>
> fs created label (null) on /dev/sdc8
> nodesize 4096 leafsize 4096 sectorsize 4096 size 9.31GB
> Btrfs v0.20-rc1-165-g82ac345
> # btrfs fi sh /dev/sdc8
> Label: none uuid: fc0bdbd0-7eed-460f-b4e9-131273b66df2
> Total devices 1 FS bytes used 28.00KB
> devid 1 size 9.31GB used 989.62MB path /dev/sdc8
>
> Btrfs v0.20-rc1-165-g82ac345
> #
>
> But we should check out the swap device. So fixed it.
I guess it's nice to parse /proc/swaps to be able to offer the
helpful error message in this case. (though I wonder how long
/proc/swaps will be available, and in this format? Does it count
as ABI?)
Your implementation looks just like the one in e2fsprogs, so it should
work fine.
But I also wonder if overall it would be safest to open the device O_EXCL,
which would fail with EBUSY if it were in use for swap, or mounted,
or opened O_EXCL by another process for any other reason:
[root@host tmp]# cat /proc/swaps
Filename Type Size Used Priority
/dev/sda3 partition 2048280 822616 -1
[root@host tmp]# strace -e open ./test
open("/etc/ld.so.cache", O_RDONLY) = 3
open("/lib64/libc.so.6", O_RDONLY) = 3
open("/dev/sda3", O_RDWR|O_EXCL) = -1 EBUSY (Device or resource busy)
open: Device or resource busy
-Eric
> Signed-off-by: Tsutomu Itoh <t-i...@jp.fujitsu.com>
> ---
> (this patch is based on Chris's raid56-experimental branch)
> ---
> mkfs.c | 18 ++++++++++++++++++
> utils.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
> utils.h | 1 +
> 3 files changed, 68 insertions(+)
>
> diff --git a/mkfs.c b/mkfs.c
> index 2d3c2af..fdc3373 100644
> --- a/mkfs.c
> +++ b/mkfs.c
> @@ -1366,6 +1366,15 @@ int main(int ac, char **av)
>
> if (source_dir == 0) {
> file = av[optind++];
> + ret = is_swap_device(file);
> + if (ret < 0) {
> + fprintf(stderr, "error checking %s status\n", file);
> + exit(1);
> + }
> + if (ret == 1) {
> + fprintf(stderr, "%s is a swap device\n", file);
> + exit(1);
> + }
> ret = check_mounted(file);
> if (ret < 0) {
> fprintf(stderr, "error checking %s mount status\n",
> file);
> @@ -1461,6 +1470,15 @@ int main(int ac, char **av)
> int old_mixed = mixed;
>
> file = av[optind++];
> + ret = is_swap_device(file);
> + if (ret < 0) {
> + fprintf(stderr, "error checking %s status\n", file);
> + exit(1);
> + }
> + if (ret == 1) {
> + fprintf(stderr, "%s is a swap device\n", file);
> + exit(1);
> + }
> ret = check_mounted(file);
> if (ret < 0) {
> fprintf(stderr, "error checking %s mount status\n",
> diff --git a/utils.c b/utils.c
> index f9ee812..0c551a0 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -1386,3 +1386,52 @@ int get_fs_info(int fd, char *path, struct
> btrfs_ioctl_fs_info_args *fi_args,
>
> return 0;
> }
> +
> +/*
> + * Checks if the swap device or not.
> + * Returns 1 if the swap device, < 0 on error or 0 if not the swap device.
> + */
> +int is_swap_device(const char *file)
> +{
> + FILE *f;
> + struct stat st_buf;
> + char buf[1024];
> + char *cp;
> + dev_t rdev;
> + int ret = 0;
> +
> + if (stat(file, &st_buf) < 0)
> + return -errno;
> + if (!S_ISBLK(st_buf.st_mode))
> + return 0;
> +
> + rdev = st_buf.st_rdev;
> +
> + if ((f = fopen("/proc/swaps", "r")) == NULL)
> + return -errno;
> +
> + /* skip the first line */
> + if (fgets(buf, sizeof(buf), f) == NULL)
> + goto out;
> +
> + while (fgets(buf, sizeof(buf), f) != NULL) {
> + if ((cp = strchr(buf, ' ')) != NULL)
> + *cp = 0;
> + if ((cp = strchr(buf, '\t')) != NULL)
> + *cp = 0;
> + if (strcmp(file, buf) == 0) {
> + ret = 1;
> + break;
> + }
> + if ((stat(buf, &st_buf) == 0) && S_ISBLK(st_buf.st_mode) &&
> + rdev == st_buf.st_rdev) {
> + ret = 1;
> + break;
> + }
> + }
> +
> +out:
> + fclose(f);
> +
> + return ret;
> +}
> diff --git a/utils.h b/utils.h
> index bbcaf6a..60a0fea 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -55,6 +55,7 @@ int get_fs_info(int fd, char *path, struct
> btrfs_ioctl_fs_info_args *fi_args,
> struct btrfs_ioctl_dev_info_args **di_ret);
>
> char *__strncpy__null(char *dest, const char *src, size_t n);
> +int is_swap_device(const char *file);
> /* Helper to always get proper size of the destination string */
> #define strncpy_null(dest, src) __strncpy__null(dest, src, sizeof(dest))
>
>
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