* [PATCH] Btrfs-progs: loopback files cannot be used if the path is too long @ 2012-10-12 13:55 nirbheek.chauhan 2012-10-12 13:55 ` [PATCH] Btrfs-progs: fix resolving of loop devices nirbheek.chauhan 0 siblings, 1 reply; 3+ messages in thread From: nirbheek.chauhan @ 2012-10-12 13:55 UTC (permalink / raw) To: linux-btrfs; +Cc: Nirbheek Chauhan From: Nirbheek Chauhan <nirbheek.chauhan@collabora.co.uk> If the path to a given loopback file is longer than 64 characters, none of the Btrfs-progs tools can use it. This is because the size of loopinfo.lo_name returned by the LOOP_GET_STATUS ioctl is 64. The attached patch fixes this by fetching the backing file for a loopback device from /sys/block; which is how `losetup` from util-linux does it as well. Nirbheek Chauhan (1): Btrfs-progs: fix resolving of loop devices utils.c | 26 ++++++++++++++------------ 1 files changed, 14 insertions(+), 12 deletions(-) -- 1.7.8.6 ^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] Btrfs-progs: fix resolving of loop devices 2012-10-12 13:55 [PATCH] Btrfs-progs: loopback files cannot be used if the path is too long nirbheek.chauhan @ 2012-10-12 13:55 ` nirbheek.chauhan 2012-10-23 9:53 ` Hector Oron 0 siblings, 1 reply; 3+ messages in thread From: nirbheek.chauhan @ 2012-10-12 13:55 UTC (permalink / raw) To: linux-btrfs; +Cc: Nirbheek Chauhan From: Nirbheek Chauhan <nirbheek.chauhan@collabora.co.uk> The LOOP_GET_STATUS ioctl truncates filenames to 64 characters. We should get the backing file for a given loop device from /sys/. This is how losetup does it as well. --- utils.c | 26 ++++++++++++++------------ 1 files changed, 14 insertions(+), 12 deletions(-) diff --git a/utils.c b/utils.c index 205e667..cdd6f7d 100644 --- a/utils.c +++ b/utils.c @@ -20,6 +20,7 @@ #define __USE_XOPEN2K #include <stdio.h> #include <stdlib.h> +#include <string.h> #ifndef __CHECKER__ #include <sys/ioctl.h> #include <sys/mount.h> @@ -651,21 +652,22 @@ int is_loop_device (const char* device) { * the associated file (e.g. /images/my_btrfs.img) */ int resolve_loop_device(const char* loop_dev, char* loop_file, int max_len) { - int loop_fd; - int ret_ioctl; - struct loop_info loopinfo; + int ret; + FILE *f; + char fmt[20]; + char p[PATH_MAX]; + char real_loop_dev[PATH_MAX]; - if ((loop_fd = open(loop_dev, O_RDONLY)) < 0) + if (!realpath(loop_dev, real_loop_dev)) + return -errno; + snprintf(p, PATH_MAX, "/sys/block/%s/loop/backing_file", strrchr(real_loop_dev, '/')); + if (!(f = fopen(p, "r"))) return -errno; - ret_ioctl = ioctl(loop_fd, LOOP_GET_STATUS, &loopinfo); - close(loop_fd); - - if (ret_ioctl == 0) { - strncpy(loop_file, loopinfo.lo_name, max_len); - if (max_len > 0) - loop_file[max_len-1] = 0; - } else + snprintf(fmt, 20, "%%%i[^\n]", max_len-1); + ret = fscanf(f, fmt, loop_file); + fclose(f); + if (ret == EOF) return -errno; return 0; -- 1.7.8.6 ^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH] Btrfs-progs: fix resolving of loop devices 2012-10-12 13:55 ` [PATCH] Btrfs-progs: fix resolving of loop devices nirbheek.chauhan @ 2012-10-23 9:53 ` Hector Oron 0 siblings, 0 replies; 3+ messages in thread From: Hector Oron @ 2012-10-23 9:53 UTC (permalink / raw) To: linux-btrfs; +Cc: nirbheek.chauhan From: Nirbheek Chauhan <nirbheek.chauhan <at> collabora.co.uk> If the path to a given loopback file is longer than 64 characters, none of the Btrfs-progs tools can use it. This is because the size of loopinfo.lo_name returned by the LOOP_GET_STATUS ioctl is 64. The attached patch fixes this by fetching the backing file for a loopback device from /sys/block; which is how `losetup` from util-linux does it as well. Nirbheek Chauhan (1): Btrfs-progs: fix resolving of loop devices utils.c | 26 ++++++++++++++------------ 1 files changed, 14 insertions(+), 12 deletions(-) Tested-By: Hector Oron <hector.oron@collabora.co.uk> diff --git a/utils.c b/utils.c index 205e667..cdd6f7d 100644 --- a/utils.c +++ b/utils.c @@ -20,6 +20,7 @@ #define __USE_XOPEN2K #include <stdio.h> #include <stdlib.h> +#include <string.h> #ifndef __CHECKER__ #include <sys/ioctl.h> #include <sys/mount.h> @@ -651,21 +652,22 @@ int is_loop_device (const char* device) { * the associated file (e.g. /images/my_btrfs.img) */ int resolve_loop_device(const char* loop_dev, char* loop_file, int max_len) { - int loop_fd; - int ret_ioctl; - struct loop_info loopinfo; + int ret; + FILE *f; + char fmt[20]; + char p[PATH_MAX]; + char real_loop_dev[PATH_MAX]; - if ((loop_fd = open(loop_dev, O_RDONLY)) < 0) + if (!realpath(loop_dev, real_loop_dev)) + return -errno; + snprintf(p, PATH_MAX, "/sys/block/%s/loop/backing_file", strrchr(real_loop_dev, '/')); + if (!(f = fopen(p, "r"))) return -errno; - ret_ioctl = ioctl(loop_fd, LOOP_GET_STATUS, &loopinfo); - close(loop_fd); - - if (ret_ioctl == 0) { - strncpy(loop_file, loopinfo.lo_name, max_len); - if (max_len > 0) - loop_file[max_len-1] = 0; - } else + snprintf(fmt, 20, "%%%i[^\n]", max_len-1); + ret = fscanf(f, fmt, loop_file); + fclose(f); + if (ret == EOF) return -errno; return 0; -- 1.7.8.6 ^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2012-10-23 9:54 UTC | newest] Thread overview: 3+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-10-12 13:55 [PATCH] Btrfs-progs: loopback files cannot be used if the path is too long nirbheek.chauhan 2012-10-12 13:55 ` [PATCH] Btrfs-progs: fix resolving of loop devices nirbheek.chauhan 2012-10-23 9:53 ` Hector Oron
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