* [PATCH v2] ubifs: allow userspace to map mounts to volumes
@ 2017-05-29 7:22 Rabin Vincent
2017-05-29 11:50 ` Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes) Richard Weinberger
0 siblings, 1 reply; 5+ messages in thread
From: Rabin Vincent @ 2017-05-29 7:22 UTC (permalink / raw
To: dedekind1, richard, adrian.hunter; +Cc: linux-mtd, linux-kernel, Rabin Vincent
From: Rabin Vincent <rabinv@axis.com>
There currently appears to be no way for userspace to find out the
underlying volume number for a mounted ubifs file system, since ubifs
uses anonymous block devices. The volume name is present in
/proc/mounts but UBI volumes can be renamed after the volume has been
mounted.
To remedy this, provide a directory in /sys/fs/ubifs named after the
underlying anonymous block device's number (obtainable by userspace via
stat(2)) and provide a link named "ubi" to the underlying UBI volume.
# mount | head -1
ubi0:rootfs on / type ubifs (rw,relatime)
# ubirename /dev/ubi0 rootfs foo
# mount | head -1
ubi0:rootfs on / type ubifs (rw,relatime)
# stat /
File: /
Size: 1520 Blocks: 0 IO Block: 4096 directory
Device: dh/13d Inode: 1 Links: 18
...
# ls -l /sys/fs/ubifs/
drwxr-xr-x 2 root root 0 May 23 09:57 0:13
drwxr-xr-x 2 root root 0 May 23 09:57 0:17
# ls -l /sys/fs/ubifs/0\:13/
lrwxrwxrwx 1 root root 0 May 23 11:45 ubi
-> ../../../devices/virtual/ubi/ubi0/ubi0_10
Signed-off-by: Rabin Vincent <rabinv@axis.com>
---
v2: export symbol to fix module build
Documentation/ABI/testing/sysfs-fs-ubifs | 6 +++
drivers/mtd/ubi/kapi.c | 13 +++++++
fs/ubifs/Makefile | 2 +-
fs/ubifs/super.c | 16 +++++++-
fs/ubifs/sysfs.c | 66 ++++++++++++++++++++++++++++++++
fs/ubifs/sysfs.h | 11 ++++++
fs/ubifs/ubifs.h | 7 ++++
include/linux/mtd/ubi.h | 3 ++
8 files changed, 122 insertions(+), 2 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-fs-ubifs
create mode 100644 fs/ubifs/sysfs.c
create mode 100644 fs/ubifs/sysfs.h
diff --git a/Documentation/ABI/testing/sysfs-fs-ubifs b/Documentation/ABI/testing/sysfs-fs-ubifs
new file mode 100644
index 0000000..1735859
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-fs-ubifs
@@ -0,0 +1,6 @@
+What: /sys/fs/ubifs/<disk>/ubi
+Date: May 2017
+Description:
+ This symbolic link points to the file system's underlying UBI
+ volume. The <disk> is the major:minor numbers of the anonymous
+ block device backing the file system.
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index d4b2e87..395dae6 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -107,6 +107,19 @@ void ubi_get_volume_info(struct ubi_volume_desc *desc,
EXPORT_SYMBOL_GPL(ubi_get_volume_info);
/**
+ * ubi_volume_kobject - get kobject for a UBI volume.
+ * @desc: volume descriptor
+ *
+ * Retrieves a pointer to the struct kobject underlying the UBI volume.
+ * The caller must hold a reference to the UBI volume.
+ */
+struct kobject *ubi_volume_kobj(struct ubi_volume_desc *desc)
+{
+ return &desc->vol->dev.kobj;
+}
+EXPORT_SYMBOL_GPL(ubi_volume_kobj);
+
+/**
* ubi_open_volume - open UBI volume.
* @ubi_num: UBI device number
* @vol_id: volume ID
diff --git a/fs/ubifs/Makefile b/fs/ubifs/Makefile
index 6f3251c..7bf4689 100644
--- a/fs/ubifs/Makefile
+++ b/fs/ubifs/Makefile
@@ -4,5 +4,5 @@ ubifs-y += shrinker.o journal.o file.o dir.o super.o sb.o io.o
ubifs-y += tnc.o master.o scan.o replay.o log.o commit.o gc.o orphan.o
ubifs-y += budget.o find.o tnc_commit.o compress.o lpt.o lprops.o
ubifs-y += recovery.o ioctl.o lpt_commit.o tnc_misc.o xattr.o debug.o
-ubifs-y += misc.o
+ubifs-y += sysfs.o misc.o
ubifs-$(CONFIG_UBIFS_FS_ENCRYPTION) += crypto.o
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index cf4cc99..fdcfefe 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1164,6 +1164,10 @@ static int mount_ubifs(struct ubifs_info *c)
if (err)
return err;
+ err = ubifs_sysfs_register(c);
+ if (err)
+ goto out_debugging;
+
err = check_volume_empty(c);
if (err)
goto out_free;
@@ -1496,6 +1500,8 @@ static int mount_ubifs(struct ubifs_info *c)
vfree(c->ileb_buf);
vfree(c->sbuf);
kfree(c->bottom_up_buf);
+ ubifs_sysfs_unregister(c);
+out_debugging:
ubifs_debugging_exit(c);
return err;
}
@@ -1536,6 +1542,7 @@ static void ubifs_umount(struct ubifs_info *c)
vfree(c->sbuf);
kfree(c->bottom_up_buf);
ubifs_debugging_exit(c);
+ ubifs_sysfs_unregister(c);
}
/**
@@ -2271,14 +2278,20 @@ static int __init ubifs_init(void)
if (err)
goto out_compr;
+ err = ubifs_sysfs_init();
+ if (err)
+ goto out_dbg;
+
err = register_filesystem(&ubifs_fs_type);
if (err) {
pr_err("UBIFS error (pid %d): cannot register file system, error %d",
current->pid, err);
- goto out_dbg;
+ goto out_sysfs;
}
return 0;
+out_sysfs:
+ ubifs_sysfs_exit();
out_dbg:
dbg_debugfs_exit();
out_compr:
@@ -2308,6 +2321,7 @@ static void __exit ubifs_exit(void)
rcu_barrier();
kmem_cache_destroy(ubifs_inode_slab);
unregister_filesystem(&ubifs_fs_type);
+ ubifs_sysfs_exit();
}
module_exit(ubifs_exit);
diff --git a/fs/ubifs/sysfs.c b/fs/ubifs/sysfs.c
new file mode 100644
index 0000000..8f2cba1
--- /dev/null
+++ b/fs/ubifs/sysfs.c
@@ -0,0 +1,66 @@
+#include <linux/fs.h>
+
+#include "ubifs.h"
+
+static struct kset *ubifs_kset;
+
+static void ubifs_sb_release(struct kobject *kobj)
+{
+ struct ubifs_info *c = container_of(kobj, struct ubifs_info, kobj);
+
+ complete(&c->kobj_unregister);
+}
+
+static struct kobj_type ubifs_sb_ktype = {
+ .sysfs_ops = &kobj_sysfs_ops,
+ .release = ubifs_sb_release,
+};
+
+int ubifs_sysfs_register(struct ubifs_info *c)
+{
+ dev_t devt = c->vfs_sb->s_dev;
+ int ret;
+
+ c->kobj.kset = ubifs_kset;
+ init_completion(&c->kobj_unregister);
+
+ ret = kobject_init_and_add(&c->kobj, &ubifs_sb_ktype, NULL,
+ "%u:%u", MAJOR(devt), MINOR(devt));
+ if (ret)
+ goto out_put;
+
+ ret = sysfs_create_link(&c->kobj, ubi_volume_kobj(c->ubi), "ubi");
+ if (ret)
+ goto out_del;
+
+ return 0;
+
+out_del:
+ kobject_del(&c->kobj);
+out_put:
+ kobject_put(&c->kobj);
+ wait_for_completion(&c->kobj_unregister);
+ return ret;
+}
+
+void ubifs_sysfs_unregister(struct ubifs_info *c)
+{
+ sysfs_remove_link(&c->kobj, "ubi");
+ kobject_del(&c->kobj);
+ kobject_put(&c->kobj);
+ wait_for_completion(&c->kobj_unregister);
+}
+
+int __init ubifs_sysfs_init(void)
+{
+ ubifs_kset = kset_create_and_add("ubifs", NULL, fs_kobj);
+ if (!ubifs_kset)
+ return -ENOMEM;
+
+ return 0;
+}
+
+void ubifs_sysfs_exit(void)
+{
+ kset_unregister(ubifs_kset);
+}
diff --git a/fs/ubifs/sysfs.h b/fs/ubifs/sysfs.h
new file mode 100644
index 0000000..4b7e70b
--- /dev/null
+++ b/fs/ubifs/sysfs.h
@@ -0,0 +1,11 @@
+#ifndef __UBIFS_SYSFS_H__
+#define __UBIFS_SYSFS_H__
+
+struct ubifs_info;
+
+int ubifs_sysfs_init(void);
+void ubifs_sysfs_exit(void);
+int ubifs_sysfs_register(struct ubifs_info *c);
+void ubifs_sysfs_unregister(struct ubifs_info *c);
+
+#endif
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 298b4d8..3a3154f 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -43,7 +43,10 @@
#else
#include <linux/fscrypt_notsupp.h>
#endif
+#include <linux/sysfs.h>
+#include <linux/completion.h>
#include <linux/random.h>
+#include "sysfs.h"
#include "ubifs-media.h"
/* Version of this UBIFS implementation */
@@ -1216,6 +1219,8 @@ struct ubifs_debug_info;
* @mount_opts: UBIFS-specific mount options
*
* @dbg: debugging-related information
+ * @kobj: kobject for /sys/fs/ubifs/
+ * @kobj_unregister: completion to unregister sysfs kobject
*/
struct ubifs_info {
struct super_block *vfs_sb;
@@ -1446,6 +1451,8 @@ struct ubifs_info {
struct ubifs_mount_opts mount_opts;
struct ubifs_debug_info *dbg;
+ struct kobject kobj;
+ struct completion kobj_unregister;
};
extern struct list_head ubifs_infos;
diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
index 1e271cb..d35e84f 100644
--- a/include/linux/mtd/ubi.h
+++ b/include/linux/mtd/ubi.h
@@ -26,6 +26,8 @@
#include <linux/scatterlist.h>
#include <mtd/ubi-user.h>
+struct kobject;
+
/* All voumes/LEBs */
#define UBI_ALL -1
@@ -241,6 +243,7 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode);
struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
int mode);
struct ubi_volume_desc *ubi_open_volume_path(const char *pathname, int mode);
+struct kobject *ubi_volume_kobj(struct ubi_volume_desc *desc);
int ubi_register_volume_notifier(struct notifier_block *nb,
int ignore_existing);
--
2.1.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes)
2017-05-29 7:22 [PATCH v2] ubifs: allow userspace to map mounts to volumes Rabin Vincent
@ 2017-05-29 11:50 ` Richard Weinberger
2017-05-29 12:08 ` Al Viro
0 siblings, 1 reply; 5+ messages in thread
From: Richard Weinberger @ 2017-05-29 11:50 UTC (permalink / raw
To: Rabin Vincent, dedekind1, adrian.hunter
Cc: linux-mtd, linux-kernel, Rabin Vincent, linux-fsdevel,
Christoph Hellwig, Al Viro
CC'ing VFS folks
Am 29.05.2017 um 09:22 schrieb Rabin Vincent:
> From: Rabin Vincent <rabinv@axis.com>
>
> There currently appears to be no way for userspace to find out the
> underlying volume number for a mounted ubifs file system, since ubifs
> uses anonymous block devices. The volume name is present in
> /proc/mounts but UBI volumes can be renamed after the volume has been
> mounted.
>
> To remedy this, provide a directory in /sys/fs/ubifs named after the
> underlying anonymous block device's number (obtainable by userspace via
> stat(2)) and provide a link named "ubi" to the underlying UBI volume.
I wonder whether it would make more sense to just assign the character device
number of the UBI volume to ->s_dev.
Then userspace can query the underlying device without additional sysfs
magic.
Sure if userspace expects a block number from UBIFS it will get confused.
Comments?
> # mount | head -1
> ubi0:rootfs on / type ubifs (rw,relatime)
> # ubirename /dev/ubi0 rootfs foo
> # mount | head -1
> ubi0:rootfs on / type ubifs (rw,relatime)
> # stat /
> File: /
> Size: 1520 Blocks: 0 IO Block: 4096 directory
> Device: dh/13d Inode: 1 Links: 18
> ...
> # ls -l /sys/fs/ubifs/
> drwxr-xr-x 2 root root 0 May 23 09:57 0:13
> drwxr-xr-x 2 root root 0 May 23 09:57 0:17
> # ls -l /sys/fs/ubifs/0\:13/
> lrwxrwxrwx 1 root root 0 May 23 11:45 ubi
> -> ../../../devices/virtual/ubi/ubi0/ubi0_10
>
> Signed-off-by: Rabin Vincent <rabinv@axis.com>
> ---
> v2: export symbol to fix module build
>
> Documentation/ABI/testing/sysfs-fs-ubifs | 6 +++
> drivers/mtd/ubi/kapi.c | 13 +++++++
> fs/ubifs/Makefile | 2 +-
> fs/ubifs/super.c | 16 +++++++-
> fs/ubifs/sysfs.c | 66 ++++++++++++++++++++++++++++++++
> fs/ubifs/sysfs.h | 11 ++++++
> fs/ubifs/ubifs.h | 7 ++++
> include/linux/mtd/ubi.h | 3 ++
> 8 files changed, 122 insertions(+), 2 deletions(-)
> create mode 100644 Documentation/ABI/testing/sysfs-fs-ubifs
> create mode 100644 fs/ubifs/sysfs.c
> create mode 100644 fs/ubifs/sysfs.h
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-ubifs b/Documentation/ABI/testing/sysfs-fs-ubifs
> new file mode 100644
> index 0000000..1735859
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-fs-ubifs
> @@ -0,0 +1,6 @@
> +What: /sys/fs/ubifs/<disk>/ubi
> +Date: May 2017
> +Description:
> + This symbolic link points to the file system's underlying UBI
> + volume. The <disk> is the major:minor numbers of the anonymous
> + block device backing the file system.
> diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
> index d4b2e87..395dae6 100644
> --- a/drivers/mtd/ubi/kapi.c
> +++ b/drivers/mtd/ubi/kapi.c
> @@ -107,6 +107,19 @@ void ubi_get_volume_info(struct ubi_volume_desc *desc,
> EXPORT_SYMBOL_GPL(ubi_get_volume_info);
>
> /**
> + * ubi_volume_kobject - get kobject for a UBI volume.
> + * @desc: volume descriptor
> + *
> + * Retrieves a pointer to the struct kobject underlying the UBI volume.
> + * The caller must hold a reference to the UBI volume.
> + */
> +struct kobject *ubi_volume_kobj(struct ubi_volume_desc *desc)
> +{
> + return &desc->vol->dev.kobj;
> +}
> +EXPORT_SYMBOL_GPL(ubi_volume_kobj);
> +
> +/**
> * ubi_open_volume - open UBI volume.
> * @ubi_num: UBI device number
> * @vol_id: volume ID
> diff --git a/fs/ubifs/Makefile b/fs/ubifs/Makefile
> index 6f3251c..7bf4689 100644
> --- a/fs/ubifs/Makefile
> +++ b/fs/ubifs/Makefile
> @@ -4,5 +4,5 @@ ubifs-y += shrinker.o journal.o file.o dir.o super.o sb.o io.o
> ubifs-y += tnc.o master.o scan.o replay.o log.o commit.o gc.o orphan.o
> ubifs-y += budget.o find.o tnc_commit.o compress.o lpt.o lprops.o
> ubifs-y += recovery.o ioctl.o lpt_commit.o tnc_misc.o xattr.o debug.o
> -ubifs-y += misc.o
> +ubifs-y += sysfs.o misc.o
> ubifs-$(CONFIG_UBIFS_FS_ENCRYPTION) += crypto.o
> diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
> index cf4cc99..fdcfefe 100644
> --- a/fs/ubifs/super.c
> +++ b/fs/ubifs/super.c
> @@ -1164,6 +1164,10 @@ static int mount_ubifs(struct ubifs_info *c)
> if (err)
> return err;
>
> + err = ubifs_sysfs_register(c);
> + if (err)
> + goto out_debugging;
> +
> err = check_volume_empty(c);
> if (err)
> goto out_free;
> @@ -1496,6 +1500,8 @@ static int mount_ubifs(struct ubifs_info *c)
> vfree(c->ileb_buf);
> vfree(c->sbuf);
> kfree(c->bottom_up_buf);
> + ubifs_sysfs_unregister(c);
> +out_debugging:
> ubifs_debugging_exit(c);
> return err;
> }
> @@ -1536,6 +1542,7 @@ static void ubifs_umount(struct ubifs_info *c)
> vfree(c->sbuf);
> kfree(c->bottom_up_buf);
> ubifs_debugging_exit(c);
> + ubifs_sysfs_unregister(c);
> }
>
> /**
> @@ -2271,14 +2278,20 @@ static int __init ubifs_init(void)
> if (err)
> goto out_compr;
>
> + err = ubifs_sysfs_init();
> + if (err)
> + goto out_dbg;
> +
> err = register_filesystem(&ubifs_fs_type);
> if (err) {
> pr_err("UBIFS error (pid %d): cannot register file system, error %d",
> current->pid, err);
> - goto out_dbg;
> + goto out_sysfs;
> }
> return 0;
>
> +out_sysfs:
> + ubifs_sysfs_exit();
> out_dbg:
> dbg_debugfs_exit();
> out_compr:
> @@ -2308,6 +2321,7 @@ static void __exit ubifs_exit(void)
> rcu_barrier();
> kmem_cache_destroy(ubifs_inode_slab);
> unregister_filesystem(&ubifs_fs_type);
> + ubifs_sysfs_exit();
> }
> module_exit(ubifs_exit);
>
> diff --git a/fs/ubifs/sysfs.c b/fs/ubifs/sysfs.c
> new file mode 100644
> index 0000000..8f2cba1
> --- /dev/null
> +++ b/fs/ubifs/sysfs.c
> @@ -0,0 +1,66 @@
> +#include <linux/fs.h>
> +
> +#include "ubifs.h"
> +
> +static struct kset *ubifs_kset;
> +
> +static void ubifs_sb_release(struct kobject *kobj)
> +{
> + struct ubifs_info *c = container_of(kobj, struct ubifs_info, kobj);
> +
> + complete(&c->kobj_unregister);
> +}
> +
> +static struct kobj_type ubifs_sb_ktype = {
> + .sysfs_ops = &kobj_sysfs_ops,
> + .release = ubifs_sb_release,
> +};
> +
> +int ubifs_sysfs_register(struct ubifs_info *c)
> +{
> + dev_t devt = c->vfs_sb->s_dev;
> + int ret;
> +
> + c->kobj.kset = ubifs_kset;
> + init_completion(&c->kobj_unregister);
> +
> + ret = kobject_init_and_add(&c->kobj, &ubifs_sb_ktype, NULL,
> + "%u:%u", MAJOR(devt), MINOR(devt));
> + if (ret)
> + goto out_put;
> +
> + ret = sysfs_create_link(&c->kobj, ubi_volume_kobj(c->ubi), "ubi");
> + if (ret)
> + goto out_del;
> +
> + return 0;
> +
> +out_del:
> + kobject_del(&c->kobj);
> +out_put:
> + kobject_put(&c->kobj);
> + wait_for_completion(&c->kobj_unregister);
> + return ret;
> +}
> +
> +void ubifs_sysfs_unregister(struct ubifs_info *c)
> +{
> + sysfs_remove_link(&c->kobj, "ubi");
> + kobject_del(&c->kobj);
> + kobject_put(&c->kobj);
> + wait_for_completion(&c->kobj_unregister);
> +}
> +
> +int __init ubifs_sysfs_init(void)
> +{
> + ubifs_kset = kset_create_and_add("ubifs", NULL, fs_kobj);
> + if (!ubifs_kset)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +void ubifs_sysfs_exit(void)
> +{
> + kset_unregister(ubifs_kset);
> +}
> diff --git a/fs/ubifs/sysfs.h b/fs/ubifs/sysfs.h
> new file mode 100644
> index 0000000..4b7e70b
> --- /dev/null
> +++ b/fs/ubifs/sysfs.h
> @@ -0,0 +1,11 @@
> +#ifndef __UBIFS_SYSFS_H__
> +#define __UBIFS_SYSFS_H__
> +
> +struct ubifs_info;
> +
> +int ubifs_sysfs_init(void);
> +void ubifs_sysfs_exit(void);
> +int ubifs_sysfs_register(struct ubifs_info *c);
> +void ubifs_sysfs_unregister(struct ubifs_info *c);
> +
> +#endif
> diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
> index 298b4d8..3a3154f 100644
> --- a/fs/ubifs/ubifs.h
> +++ b/fs/ubifs/ubifs.h
> @@ -43,7 +43,10 @@
> #else
> #include <linux/fscrypt_notsupp.h>
> #endif
> +#include <linux/sysfs.h>
> +#include <linux/completion.h>
> #include <linux/random.h>
> +#include "sysfs.h"
> #include "ubifs-media.h"
>
> /* Version of this UBIFS implementation */
> @@ -1216,6 +1219,8 @@ struct ubifs_debug_info;
> * @mount_opts: UBIFS-specific mount options
> *
> * @dbg: debugging-related information
> + * @kobj: kobject for /sys/fs/ubifs/
> + * @kobj_unregister: completion to unregister sysfs kobject
> */
> struct ubifs_info {
> struct super_block *vfs_sb;
> @@ -1446,6 +1451,8 @@ struct ubifs_info {
> struct ubifs_mount_opts mount_opts;
>
> struct ubifs_debug_info *dbg;
> + struct kobject kobj;
> + struct completion kobj_unregister;
> };
>
> extern struct list_head ubifs_infos;
> diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
> index 1e271cb..d35e84f 100644
> --- a/include/linux/mtd/ubi.h
> +++ b/include/linux/mtd/ubi.h
> @@ -26,6 +26,8 @@
> #include <linux/scatterlist.h>
> #include <mtd/ubi-user.h>
>
> +struct kobject;
> +
> /* All voumes/LEBs */
> #define UBI_ALL -1
>
> @@ -241,6 +243,7 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode);
> struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
> int mode);
> struct ubi_volume_desc *ubi_open_volume_path(const char *pathname, int mode);
> +struct kobject *ubi_volume_kobj(struct ubi_volume_desc *desc);
>
> int ubi_register_volume_notifier(struct notifier_block *nb,
> int ignore_existing);
>
Thanks,
//richard
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes)
2017-05-29 11:50 ` Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes) Richard Weinberger
@ 2017-05-29 12:08 ` Al Viro
2017-05-29 14:33 ` Rabin Vincent
0 siblings, 1 reply; 5+ messages in thread
From: Al Viro @ 2017-05-29 12:08 UTC (permalink / raw
To: Richard Weinberger
Cc: Rabin Vincent, dedekind1, adrian.hunter, linux-mtd, linux-kernel,
Rabin Vincent, linux-fsdevel, Christoph Hellwig
On Mon, May 29, 2017 at 01:50:30PM +0200, Richard Weinberger wrote:
> CC'ing VFS folks
>
> Am 29.05.2017 um 09:22 schrieb Rabin Vincent:
> > From: Rabin Vincent <rabinv@axis.com>
> >
> > There currently appears to be no way for userspace to find out the
> > underlying volume number for a mounted ubifs file system, since ubifs
> > uses anonymous block devices. The volume name is present in
> > /proc/mounts but UBI volumes can be renamed after the volume has been
> > mounted.
> >
> > To remedy this, provide a directory in /sys/fs/ubifs named after the
> > underlying anonymous block device's number (obtainable by userspace via
> > stat(2)) and provide a link named "ubi" to the underlying UBI volume.
>
> I wonder whether it would make more sense to just assign the character device
> number of the UBI volume to ->s_dev.
> Then userspace can query the underlying device without additional sysfs
> magic.
>
> Sure if userspace expects a block number from UBIFS it will get confused.
>
> Comments?
Userspace sure as hell does. st_dev in stat(2) is a block device number;
moreover, there might _be_ a block device with the same number at the same
time - even mounted. Why not make ->show_options() print the currently
valid volume name, anyway? That would seem to be the obvious approach...
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes)
2017-05-29 12:08 ` Al Viro
@ 2017-05-29 14:33 ` Rabin Vincent
2017-05-29 19:37 ` Richard Weinberger
0 siblings, 1 reply; 5+ messages in thread
From: Rabin Vincent @ 2017-05-29 14:33 UTC (permalink / raw
To: Al Viro, Richard Weinberger
Cc: dedekind1, adrian.hunter, linux-mtd, linux-kernel, linux-fsdevel,
Christoph Hellwig
On Mon, May 29, 2017 at 01:08:25PM +0100, Al Viro wrote:
> Userspace sure as hell does. st_dev in stat(2) is a block device number;
> moreover, there might _be_ a block device with the same number at the same
> time - even mounted. Why not make ->show_options() print the currently
> valid volume name, anyway? That would seem to be the obvious approach...
The following patch works for me, if it's OK to show options that can't
actually be used when mounting:
8<-----------------------
>From 19797334f9c87a2e0c90fe2c93f29cce397b6230 Mon Sep 17 00:00:00 2001
From: Rabin Vincent <rabinv@axis.com>
Date: Mon, 29 May 2017 16:08:44 +0200
Subject: [PATCH v3] ubifs: allow userspace to map mounts to volumes
There currently appears to be no way for userspace to find out the
underlying volume number for a mounted ubifs file system, since ubifs
uses anonymous block devices. The volume name is present in
/proc/mounts but UBI volumes can be renamed after the volume has been
mounted.
To remedy this, show the UBI number and UBI volume number as part of the
options visible under /proc/mounts.
# mount -t ubifs ubi:baz x
# mount
ubi:baz on /root/x type ubifs (rw,relatime,ubi=0,vol=2)
# ubirename /dev/ubi0 baz bazz
# mount
ubi:baz on /root/x type ubifs (rw,relatime,ubi=0,vol=2)
# ubinfo -d 0 -n 2
Volume ID: 2 (on ubi0)
Type: dynamic
Alignment: 1
Size: 67 LEBs (1063424 bytes, 1.0 MiB)
State: OK
Name: bazz
Character device major/minor: 254:3
Signed-off-by: Rabin Vincent <rabinv@axis.com>
---
fs/ubifs/super.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index cf4cc99..4b54186 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -446,6 +446,8 @@ static int ubifs_show_options(struct seq_file *s, struct dentry *root)
ubifs_compr_name(c->mount_opts.compr_type));
}
+ seq_printf(s, ",ubi=%d,vol=%d", c->vi.ubi_num, c->vi.vol_id);
+
return 0;
}
--
2.1.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes)
2017-05-29 14:33 ` Rabin Vincent
@ 2017-05-29 19:37 ` Richard Weinberger
0 siblings, 0 replies; 5+ messages in thread
From: Richard Weinberger @ 2017-05-29 19:37 UTC (permalink / raw
To: Rabin Vincent, Al Viro
Cc: dedekind1, adrian.hunter, linux-mtd, linux-kernel, linux-fsdevel,
Christoph Hellwig
Rabin,
Am 29.05.2017 um 16:33 schrieb Rabin Vincent:
> On Mon, May 29, 2017 at 01:08:25PM +0100, Al Viro wrote:
>> Userspace sure as hell does. st_dev in stat(2) is a block device number;
>> moreover, there might _be_ a block device with the same number at the same
>> time - even mounted. Why not make ->show_options() print the currently
>> valid volume name, anyway? That would seem to be the obvious approach...
>
> The following patch works for me, if it's OK to show options that can't
> actually be used when mounting:
Good that this very small changes fulfils your use case. :-)
I'd accept and ignore ubi= and vol= parameters.
i.e.
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index cf4cc99b75b5..50cebbe35c38 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -931,6 +933,7 @@ enum {
Opt_chk_data_crc,
Opt_no_chk_data_crc,
Opt_override_compr,
+ Opt_ignore,
Opt_err,
};
@@ -942,6 +945,8 @@ static const match_table_t tokens = {
{Opt_chk_data_crc, "chk_data_crc"},
{Opt_no_chk_data_crc, "no_chk_data_crc"},
{Opt_override_compr, "compr=%s"},
+ {Opt_ignore, "ubi=%s"},
+ {Opt_ignore, "vol=%s"},
{Opt_err, NULL},
};
@@ -1042,6 +1047,8 @@ static int ubifs_parse_options(struct ubifs_info *c, char *options,
c->default_compr = c->mount_opts.compr_type;
break;
}
+ case Opt_ignore:
+ break;
default:
{
unsigned long flag;
Thanks,
//richard
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-05-29 19:37 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-05-29 7:22 [PATCH v2] ubifs: allow userspace to map mounts to volumes Rabin Vincent
2017-05-29 11:50 ` Setting ->s_dev to a char device (Was: Re: [PATCH v2] ubifs: allow userspace to map mounts to volumes) Richard Weinberger
2017-05-29 12:08 ` Al Viro
2017-05-29 14:33 ` Rabin Vincent
2017-05-29 19:37 ` Richard Weinberger
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.