From e905a3656199b6f544127b4ffb8b2d2744b53638 Mon Sep 17 00:00:00 2001 From: Milan Broz Date: Sun, 13 Mar 2011 23:51:33 +0000 Subject: [PATCH] Prefer sysfs when reading backing file. git-svn-id: https://cryptsetup.googlecode.com/svn/trunk@457 36d66b0a-2a48-0410-832c-cd162a569da5 --- lib/utils_loop.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/lib/utils_loop.c b/lib/utils_loop.c index d628470..65656bb 100644 --- a/lib/utils_loop.c +++ b/lib/utils_loop.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -120,7 +121,7 @@ int crypt_loop_detach(const char *loop) return r; } -char *crypt_loop_backing_file(const char *loop) +static char *_ioctl_backing_file(const char *loop) { struct loop_info64 lo64 = {0}; int loop_fd; @@ -142,6 +143,38 @@ char *crypt_loop_backing_file(const char *loop) return strdup((char*)lo64.lo_file_name); } +static char *_sysfs_backing_file(const char *loop) +{ + struct stat st; + char buf[PATH_MAX]; + size_t len; + int fd; + + if (stat(loop, &st) || !S_ISBLK(st.st_mode)) + return NULL; + + snprintf(buf, sizeof(buf), "/sys/dev/block/%d:%d/loop/backing_file", + major(st.st_rdev), minor(st.st_rdev)); + + fd = open(buf, O_RDONLY); + if (fd < 0) + return NULL; + + len = read(fd, buf, PATH_MAX); + close(fd); + if (len < 2) + return NULL; + + buf[len - 1] = '\0'; + return strdup(buf); +} + +char *crypt_loop_backing_file(const char *loop) +{ + char *bf = _sysfs_backing_file(loop); + return bf ?: _ioctl_backing_file(loop); +} + int crypt_loop_device(const char *loop) { struct stat st; -- 2.7.4