libmount: add mount support for loopdevs

Signed-off-by: Karel Zak <kzak@redhat.com>

7 files changed, 261 insertions, 26 deletions

diff --git a/libmount/src/Makefile.am b/libmount/src/Makefile.am
index 56b0c207d..5525ba279 100644
--- a/libmount/src/Makefile.am
+++ b/libmount/src/Makefile.am
@@ -13,13 +13,17 @@ libmount_la_SOURCES =	mountP.h version.c utils.c test.c init.c cache.c \
 			optstr.c optmap.c iter.c lock.c \
 			fs.c tab.c tab_parse.c tab_update.c tab_diff.c \
 			context.c context_mount.c context_umount.c \
+			context_loopdev.c \
 			$(mountinc_HEADERS) \
 			$(top_srcdir)/lib/at.c \
 			$(top_srcdir)/include/list.h \
 			$(top_srcdir)/lib/mangle.c \
 			$(top_srcdir)/lib/canonicalize.c \
 			$(top_srcdir)/lib/strutils.c \
-			$(top_srcdir)/lib/env.c
+			$(top_srcdir)/lib/env.c \
+			$(top_srcdir)/lib/loopdev.c \
+			$(top_srcdir)/lib/sysfs.c \
+			$(top_srcdir)/lib/linux_version.c
 
 nodist_libmount_la_SOURCES = mountP.h
 
diff --git a/libmount/src/cache.c b/libmount/src/cache.c
index 4775069c0..907e048d0 100644
--- a/libmount/src/cache.c
+++ b/libmount/src/cache.c
@@ -237,7 +237,6 @@ static int mnt_cache_get_probe(struct libmnt_cache *cache, const char *devname,
 	blkid_probe pr = cache ? cache->pr : NULL;
 
 	assert(devname);
-	assert(res);
 
 	if (cache && cache->pr && (!cache->filename ||
 				   strcmp(devname, cache->filename))) {
@@ -260,7 +259,8 @@ static int mnt_cache_get_probe(struct libmnt_cache *cache, const char *devname,
 
 	}
 
-	*res = pr;
+	if (res)
+		*res = pr;
 	return 0;
 }
 
@@ -277,7 +277,6 @@ static int mnt_cache_get_probe(struct libmnt_cache *cache, const char *devname,
 int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname)
 {
 	int i, ntags = 0, rc;
-	blkid_probe pr;
 	const char *tags[] = { "LABEL", "UUID", "TYPE" };
 
 	assert(cache);
@@ -298,7 +297,7 @@ int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname)
 			return 0;
 	}
 
-	rc = mnt_cache_get_probe(cache, devname, &pr);
+	rc = mnt_cache_get_probe(cache, devname, NULL);
 	if (rc)
 		return rc;
 
diff --git a/libmount/src/context.c b/libmount/src/context.c
index 6b0edc55b..d65c8f152 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -61,6 +61,7 @@ struct libmnt_context *mnt_new_context(void)
 
 	cxt->syscall_status = 1;	/* not called yet */
 	cxt->helper_exec_status = 1;
+	cxt->loopdev_fd = -1;
 
 	/* if we're really root and aren't running setuid */
 	cxt->restricted = (uid_t) 0 == ruid && ruid == euid ? 0 : 1;
@@ -90,8 +91,6 @@ void mnt_free_context(struct libmnt_context *cxt)
 
 	mnt_reset_context(cxt);
 
-	DBG(CXT, mnt_debug_h(cxt, "free"));
-
 	free(cxt->fstype_pattern);
 	free(cxt->optstr_pattern);
 
@@ -100,9 +99,11 @@ void mnt_free_context(struct libmnt_context *cxt)
 	if (!(cxt->flags & MNT_FL_EXTERN_CACHE))
 		mnt_free_cache(cxt->cache);
 
+	mnt_context_clear_loopdev(cxt);
 	mnt_free_lock(cxt->lock);
 	mnt_free_update(cxt->update);
 
+	DBG(CXT, mnt_debug_h(cxt, "free"));
 	free(cxt);
 }
 
@@ -133,6 +134,11 @@ int mnt_reset_context(struct libmnt_context *cxt)
 	if (!cxt)
 		return -EINVAL;
 
+	DBG(CXT, mnt_debug_h(cxt,
+		"reset [status=%d %s]",
+		mnt_context_get_status(cxt),
+		mnt_context_get_status(cxt) == 0 ? "FAILED" : "SUCCESS"));
+
 	fl = cxt->flags;
 
 	if (!(cxt->flags & MNT_FL_EXTERN_FS))
@@ -933,21 +939,6 @@ int mnt_context_get_user_mflags(struct libmnt_context *cxt, unsigned long *flags
 	return rc;
 }
 
-static int is_loop(struct libmnt_context *cxt)
-{
-	unsigned long fl = 0;
-
-	if (cxt->user_mountflags & MNT_MS_LOOP)
-		return 1;
-	if (!mnt_context_get_mflags(cxt, &fl) && (fl & MNT_MS_LOOP))
-		return 1;
-
-	/* TODO:
-	 *	- support MNT_MS_{OFFSET,SIZELIMIT,ENCRYPTION}
-	 */
-	return 0;
-}
-
 /**
  * mnt_context_set_mountdata:
  * @cxt: mount context
@@ -1037,11 +1028,14 @@ int mnt_context_prepare_srcpath(struct libmnt_context *cxt)
 	/*
 	 * Initialize loop device
 	 */
-	if (is_loop(cxt)) {
-		; /* TODO */
+	if (mnt_context_is_loopdev(cxt)) {
+		rc = mnt_context_setup_loopdev(cxt);
+		if (rc)
+			return rc;
 	}
 
-	DBG(CXT, mnt_debug_h(cxt, "final srcpath '%s'", path));
+	DBG(CXT, mnt_debug_h(cxt, "final srcpath '%s'",
+				mnt_fs_get_source(cxt->fs)));
 	return 0;
 }
 
@@ -1474,7 +1468,7 @@ int mnt_context_apply_fstab(struct libmnt_context *cxt)
  * mnt_context_get_status:
  * @cxt: mount context
  *
- * Returns: 0 if /sbin/mount.type or mount(2) syscall was successfull.
+ * Returns: 1 if /sbin/mount.type or mount(2) syscall was successfull.
  */
 int mnt_context_get_status(struct libmnt_context *cxt)
 {
diff --git a/libmount/src/context_loopdev.c b/libmount/src/context_loopdev.c
new file mode 100644
index 000000000..6ed0df13e
--- /dev/null
+++ b/libmount/src/context_loopdev.c
@@ -0,0 +1,227 @@
+/*
+ * Copyright (C) 2011 Karel Zak <kzak@redhat.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ */
+
+/*
+ * DOCS: - "lo@" prefix for fstype is unsupported
+ *	 - encyption= mount option for loop device is unssuported
+ */
+
+#include <blkid.h>
+
+#include "mountP.h"
+#include "loopdev.h"
+#include "linux_version.h"
+
+
+int mnt_context_is_loopdev(struct libmnt_context *cxt)
+{
+	const char *type, *src;
+	int fl;
+
+	assert(cxt);
+	/* The mount flags have to be merged, otherwise we have to use
+	 * expensive mnt_context_get_user_mflags() instead of cxt->user_mountflags. */
+	assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
+
+	if (!cxt->fs)
+		return 0;
+	src = mnt_fs_get_srcpath(cxt->fs);
+	if (!src)
+		return 0;		/* backing file not set */
+
+	if (cxt->user_mountflags & (MNT_MS_LOOP |
+				    MNT_MS_OFFSET |
+				    MNT_MS_SIZELIMIT))
+		return 1;
+
+	if (cxt->mountflags & (MS_BIND | MS_MOVE | MS_PROPAGATION))
+		return 0;
+
+	/* Automatically create a loop device from a regular file if a filesystem
+	 * is not specified or the filesystem is known for libblkid (these
+	 * filesystems work with block devices only).
+	 *
+	 * Note that there is not a restriction (on kernel side) that prevents regular
+	 * file as a mount(2) source argument. A filesystem that is able to mount
+	 * regular files could be implemented.
+	 */
+	type = mnt_fs_get_fstype(cxt->fs);
+	fl = __mnt_fs_get_flags(cxt->fs);
+
+	if (!(fl && (MNT_FS_PSEUDO | MNT_FS_NET | MNT_FS_SWAP)) &&
+	    (!type || strcmp(type, "auto") == 0 || blkid_known_fstype(type))) {
+		struct stat st;
+
+		if (stat(src, &st) || !S_ISREG(st.st_mode))
+			return 0;
+	}
+
+	return 1;
+}
+
+int mnt_context_setup_loopdev(struct libmnt_context *cxt)
+{
+	const char *backing_file;
+	char *loopdev = NULL;
+	size_t len;
+	struct loopdev_cxt lc;
+	int rc, lo_flags = 0;
+
+	assert(cxt);
+	assert(cxt->fs);
+	assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
+
+	backing_file = mnt_fs_get_srcpath(cxt->fs);
+	if (!backing_file)
+		return -EINVAL;
+
+	DBG(CXT, mnt_debug_h(cxt, "trying to setup loopdev for %s", backing_file));
+
+	if (cxt->mountflags & MS_RDONLY) {
+		DBG(CXT, mnt_debug_h(cxt, "enabling READ-ONLY flag"));
+		lo_flags |= LO_FLAGS_READ_ONLY;
+	}
+	loopcxt_init(&lc, 0);
+
+	
+	if ((cxt->user_mountflags & MNT_MS_LOOP) &&
+	    mnt_fs_get_option(cxt->fs, "loop", &loopdev, &len) == 0 && loopdev) {
+
+		char *tmp = strndup(loopdev, len);
+		if (!tmp)
+			rc = -ENOMEM;
+		else {
+			rc = loopcxt_set_device(&lc, tmp);
+			free(tmp);
+		}
+	}
+
+	/* since 2.6.37 we don't have to store backing filename to mtab
+	 * because kernel provides the name in /sys.
+	 */
+	if (get_linux_version() >= KERNEL_VERSION(2, 6, 37) ||
+	    !cxt->mtab_writable) {
+		DBG(CXT, mnt_debug_h(cxt, "enabling AUTOCLEAR flag"));
+		lo_flags |= LO_FLAGS_AUTOCLEAR;
+	}
+
+	do {
+		/* found free device */
+		if (!loopdev) {
+			rc = loopcxt_find_unused(&lc);
+			if (rc)
+				goto done;
+			DBG(CXT, mnt_debug_h(cxt, "trying to use %s",
+						loopcxt_get_device(&lc)));
+		}
+
+		/* set device attributes */
+		rc = loopcxt_set_backing_file(&lc, backing_file);
+		if (rc)
+			goto done;
+
+		loopcxt_set_flags(&lc, lo_flags);
+
+		/* setup the device */
+		rc = loopcxt_setup_device(&lc);
+		if (!rc)
+			break;		/* success */
+
+		if (loopdev || rc != -EBUSY) {
+			DBG(CXT, mnt_debug_h(cxt, "failed to setup device"));
+			break;
+		}
+		DBG(CXT, mnt_debug_h(cxt, "loopdev stolen...trying again"));
+	} while (1);
+
+	if (!rc)
+		rc = mnt_fs_set_source(cxt->fs, loopcxt_get_device(&lc));
+
+	if (!rc) {
+		/* success */
+		cxt->flags |= MNT_FL_LOOPDEV_READY;
+
+		if ((cxt->user_mountflags & MNT_MS_LOOP) &&
+		    loopcxt_is_autoclear(&lc))
+			/*
+			 * autoclear flag accepted by kernel, don't store
+			 * the "loop=" option to mtab.
+			 */
+			cxt->user_mountflags &= ~MNT_MS_LOOP;
+
+		if (!(cxt->mountflags & MS_RDONLY) &&
+		    loopcxt_is_readonly(&lc))
+			/*
+			 * mount planned read-write, but loopdev is read-only,
+			 * let's fix mount options...
+			 */
+			cxt->mountflags |= MS_RDONLY;
+
+
+		/* we have to keep the device open until mount(1),
+		 * otherwise it will auto-cleared by kernel
+		 */
+		cxt->loopdev_fd = loopcxt_get_fd(&lc);
+		loopcxt_set_fd(&lc, -1, 0);
+	}
+done:
+	loopcxt_deinit(&lc);
+	return rc;
+}
+
+/*
+ * Deletes loop device
+ */
+int mnt_context_delete_loopdev(struct libmnt_context *cxt)
+{
+	const char *src;
+	int rc;
+
+	assert(cxt);
+	assert(cxt->fs);
+
+	src = mnt_fs_get_srcpath(cxt->fs);
+	if (!src)
+		return -EINVAL;
+
+	if (cxt->loopdev_fd > -1)
+		close(cxt->loopdev_fd);
+
+	rc = loopdev_delete(src);
+	cxt->flags &= ~MNT_FL_LOOPDEV_READY;
+	cxt->loopdev_fd = -1;
+
+	DBG(CXT, mnt_debug_h(cxt, "loopdev deleted [rc=%d]", rc));
+	return rc;
+}
+
+/*
+ * Clears loopdev stuff in context, should be called after
+ * failed or successful mount(2).
+ */
+int mnt_context_clear_loopdev(struct libmnt_context *cxt)
+{
+	assert(cxt);
+
+	if (mnt_context_get_status(cxt) == 0 &&
+	    (cxt->flags & MNT_FL_LOOPDEV_READY)) {
+		/*
+		 * mount(2) failed, delete loopdev
+		 */
+		mnt_context_delete_loopdev(cxt);
+
+	} else if (cxt->loopdev_fd > -1) {
+		/*
+		 * mount(2) success, close the device
+		 */
+		DBG(CXT, mnt_debug_h(cxt, "closing loopdev FD"));
+		close(cxt->loopdev_fd);
+	}
+	cxt->loopdev_fd = -1;
+	return 0;
+}
+
diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index 15222083f..18d0739ca 100644
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -466,6 +466,8 @@ extern int mnt_context_set_syscall_status(struct libmnt_context *cxt, int status
 #define MNT_MS_UHELPER  (1 << 11)
 #define MNT_MS_HELPER   (1 << 12)
 #define MNT_MS_XCOMMENT (1 << 13)
+#define MNT_MS_OFFSET   (1 << 14)
+#define MNT_MS_SIZELIMIT (1 << 15)
 
 /*
  * mount(2) MS_* masks (MNT_MAP_LINUX map)
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 0a8c7522c..8c63fbd4e 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -259,6 +259,7 @@ struct libmnt_context
 	struct libmnt_table *mtab;	/* mtab entries */
 
 	int	optsmode;	/* fstab optstr mode MNT_OPTSMODE_{AUTO,FORCE,IGNORE} */
+	int	loopdev_fd;	/* open loopdev */
 
 	unsigned long	mountflags;	/* final mount(2) flags */
 	const void	*mountdata;	/* final mount(2) data, string or binary data */
@@ -309,6 +310,7 @@ struct libmnt_context
 #define MNT_FL_SAVED_USER	(1 << 23)
 #define MNT_FL_PREPARED		(1 << 24)
 #define MNT_FL_HELPER		(1 << 25)	/* [u]mount.<type> */
+#define MNT_FL_LOOPDEV_READY	(1 << 26)	/* /dev/loop<N> initialized by library */
 
 /* default flags */
 #define MNT_FL_DEFAULT		0
@@ -349,6 +351,11 @@ extern int mnt_context_update_tabs(struct libmnt_context *cxt);
 extern int mnt_context_umount_setopt(struct libmnt_context *cxt, int c, char *arg);
 extern int mnt_context_mount_setopt(struct libmnt_context *cxt, int c, char *arg);
 
+extern int mnt_context_is_loopdev(struct libmnt_context *cxt);
+extern int mnt_context_setup_loopdev(struct libmnt_context *cxt);
+extern int mnt_context_delete_loopdev(struct libmnt_context *cxt);
+extern int mnt_context_clear_loopdev(struct libmnt_context *cxt);
+
 /* tab_update.c */
 extern struct libmnt_fs *mnt_update_get_fs(struct libmnt_update *upd);
 extern int mnt_update_set_filename(struct libmnt_update *upd,
diff --git a/libmount/src/optmap.c b/libmount/src/optmap.c
index 7db6d0314..1ee55222a 100644
--- a/libmount/src/optmap.c
+++ b/libmount/src/optmap.c
@@ -151,6 +151,8 @@ static const struct libmnt_optmap userspace_opts_map[] =
    { "x-",      MNT_MS_XCOMMENT, MNT_NOMTAB | MNT_PREFIX }, /* x- options */
 
    { "loop[=]", MNT_MS_LOOP },                             /* use the loop device */
+   { "offset=", MNT_MS_OFFSET, MNT_NOMTAB },		   /* loop device offset */
+   { "sizelimit=", MNT_MS_SIZELIMIT, MNT_NOMTAB },	   /* loop device size limit */
 
    { "nofail",  MNT_MS_NOFAIL, MNT_NOMTAB },               /* Do not fail if ENOENT on dev */