[PATCH 13/24] init: improve the name_to_dev_t interface

From: Christoph Hellwig
Date: Wed May 31 2023 - 08:58:13 EST

name_to_dev_t has a very misleading name, that doesn't make clear
it should only be used by the early init code, and also has a bad
calling convention that doesn't allow returning different kinds of
errors. Rename it to early_lookup_bdev to make the use case clear,
and return an errno, where -EINVAL means the string could not be
parsed, and -ENODEV means it the string was valid, but there was
no device found for it.

Also stub out the whole call for !CONFIG_BLOCK as all the non-block
root cases are always covered in the caller.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
.../admin-guide/kernel-parameters.txt | 4 +-
drivers/md/dm-table.c | 5 +-
drivers/md/md-autodetect.c | 3 +-
drivers/mtd/devices/block2mtd.c | 3 +-
fs/pstore/blk.c | 4 +-
include/linux/blkdev.h | 5 +
include/linux/mount.h | 1 -
init/do_mounts.c | 102 +++++++++---------
kernel/power/hibernate.c | 22 ++--
9 files changed, 74 insertions(+), 75 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 457c342d15977e..a6bc31349cbb76 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5453,8 +5453,8 @@

root= [KNL] Root filesystem
Usually this a a block device specifier of some kind,
- see the name_to_dev_t comment in init/do_mounts.c for
- details.
+ see the early_lookup_bdev comment in init/do_mounts.c
+ for details.
Alternatively this can be "ram" for the legacy initial
ramdisk, "nfs" and "cifs" for root on a network file
system, or "mtd" and "ubi" for mounting from raw flash.
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 1398f1d6e83e7f..05aa16da43b0d5 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -330,8 +330,9 @@ dev_t dm_get_dev_t(const char *path)
{
dev_t dev;

- if (lookup_bdev(path, &dev))
- dev = name_to_dev_t(path);
+ if (lookup_bdev(path, &dev) &&
+ early_lookup_bdev(path, &dev))
+ return 0;
return dev;
}
EXPORT_SYMBOL_GPL(dm_get_dev_t);
diff --git a/drivers/md/md-autodetect.c b/drivers/md/md-autodetect.c
index 91836e6de3260f..6eaa0eab40f962 100644
--- a/drivers/md/md-autodetect.c
+++ b/drivers/md/md-autodetect.c
@@ -147,7 +147,8 @@ static void __init md_setup_drive(struct md_setup_args *args)
if (p)
*p++ = 0;

- dev = name_to_dev_t(devname);
+ if (early_lookup_bdev(devname, &dev))
+ dev = 0;
if (strncmp(devname, "/dev/", 5) == 0)
devname += 5;
snprintf(comp_name, 63, "/dev/%s", devname);
diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
index 4cd37ec45762b6..4c21e9f13bead5 100644
--- a/drivers/mtd/devices/block2mtd.c
+++ b/drivers/mtd/devices/block2mtd.c
@@ -254,8 +254,7 @@ static struct block2mtd_dev *add_device(char *devname, int erase_size,
msleep(1000);
wait_for_device_probe();

- devt = name_to_dev_t(devname);
- if (!devt)
+ if (early_lookup_bdev(devname, &devt))
continue;
bdev = blkdev_get_by_dev(devt, mode, dev);
}
diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
index 4ae0cfcd15f20b..de8cf5d75f34d5 100644
--- a/fs/pstore/blk.c
+++ b/fs/pstore/blk.c
@@ -263,9 +263,9 @@ static __init const char *early_boot_devpath(const char *initial_devname)
* same scheme to find the device that we use for mounting
* the root file system.
*/
- dev_t dev = name_to_dev_t(initial_devname);
+ dev_t dev;

- if (!dev) {
+ if (early_lookup_bdev(initial_devname, &dev)) {
pr_err("failed to resolve '%s'!\n", initial_devname);
return initial_devname;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d89c2da1469872..0bda6cb98d7eb8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1495,6 +1495,7 @@ int sync_blockdev_nowait(struct block_device *bdev);
void sync_bdevs(bool wait);
void bdev_statx_dioalign(struct inode *inode, struct kstat *stat);
void printk_all_partitions(void);
+int early_lookup_bdev(const char *pathname, dev_t *dev);
#else
static inline void invalidate_bdev(struct block_device *bdev)
{
@@ -1516,6 +1517,10 @@ static inline void bdev_statx_dioalign(struct inode *inode, struct kstat *stat)
static inline void printk_all_partitions(void)
{
}
+static inline int early_lookup_bdev(const char *pathname, dev_t *dev)
+{
+ return -EINVAL;
+}
#endif /* CONFIG_BLOCK */

int fsync_bdev(struct block_device *bdev);
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 1ea326c368f726..4b81ea90440e45 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -107,7 +107,6 @@ extern struct vfsmount *vfs_submount(const struct dentry *mountpoint,
extern void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list);
extern void mark_mounts_for_expiry(struct list_head *mounts);

-extern dev_t name_to_dev_t(const char *name);
extern bool path_is_mountpoint(const struct path *path);

extern bool our_mnt(struct vfsmount *mnt);
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 86599faf2bf8a1..f1953aeb321978 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -96,11 +96,10 @@ static int match_dev_by_uuid(struct device *dev, const void *data)
*
* Returns the matching dev_t on success or 0 on failure.
*/
-static dev_t devt_from_partuuid(const char *uuid_str)
+static int devt_from_partuuid(const char *uuid_str, dev_t *devt)
{
struct uuidcmp cmp;
struct device *dev = NULL;
- dev_t devt = 0;
int offset = 0;
char *slash;

@@ -124,21 +123,21 @@ static dev_t devt_from_partuuid(const char *uuid_str)

dev = class_find_device(&block_class, NULL, &cmp, &match_dev_by_uuid);
if (!dev)
- return 0;
+ return -ENODEV;

if (offset) {
/*
* Attempt to find the requested partition by adding an offset
* to the partition number found by UUID.
*/
- devt = part_devt(dev_to_disk(dev),
- dev_to_bdev(dev)->bd_partno + offset);
+ *devt = part_devt(dev_to_disk(dev),
+ dev_to_bdev(dev)->bd_partno + offset);
} else {
- devt = dev->devt;
+ *devt = dev->devt;
}

put_device(dev);
- return devt;
+ return 0;

clear_root_wait:
pr_err("VFS: PARTUUID= is invalid.\n"
@@ -146,7 +145,7 @@ static dev_t devt_from_partuuid(const char *uuid_str)
if (root_wait)
pr_err("Disabling rootwait; root= is invalid.\n");
root_wait = 0;
- return 0;
+ return -EINVAL;
}

/**
@@ -166,38 +165,35 @@ static int match_dev_by_label(struct device *dev, const void *data)
return 1;
}

-static dev_t devt_from_partlabel(const char *label)
+static int devt_from_partlabel(const char *label, dev_t *devt)
{
struct device *dev;
- dev_t devt = 0;

dev = class_find_device(&block_class, NULL, label, &match_dev_by_label);
- if (dev) {
- devt = dev->devt;
- put_device(dev);
- }
-
- return devt;
+ if (!dev)
+ return -ENODEV;
+ *devt = dev->devt;
+ put_device(dev);
+ return 0;
}

-static dev_t devt_from_devname(const char *name)
+static int devt_from_devname(const char *name, dev_t *devt)
{
- dev_t devt = 0;
int part;
char s[32];
char *p;

if (strlen(name) > 31)
- return 0;
+ return -EINVAL;
strcpy(s, name);
for (p = s; *p; p++) {
if (*p == '/')
*p = '!';
}

- devt = blk_lookup_devt(s, 0);
- if (devt)
- return devt;
+ *devt = blk_lookup_devt(s, 0);
+ if (*devt)
+ return 0;

/*
* Try non-existent, but valid partition, which may only exist after
@@ -206,41 +202,42 @@ static dev_t devt_from_devname(const char *name)
while (p > s && isdigit(p[-1]))
p--;
if (p == s || !*p || *p == '0')
- return 0;
+ return -EINVAL;

/* try disk name without <part number> */
part = simple_strtoul(p, NULL, 10);
*p = '\0';
- devt = blk_lookup_devt(s, part);
- if (devt)
- return devt;
+ *devt = blk_lookup_devt(s, part);
+ if (*devt)
+ return 0;

/* try disk name without p<part number> */
if (p < s + 2 || !isdigit(p[-2]) || p[-1] != 'p')
- return 0;
+ return -EINVAL;
p[-1] = '\0';
- return blk_lookup_devt(s, part);
+ *devt = blk_lookup_devt(s, part);
+ if (*devt)
+ return 0;
+ return -EINVAL;
}
-#endif /* CONFIG_BLOCK */

-static dev_t devt_from_devnum(const char *name)
+static int devt_from_devnum(const char *name, dev_t *devt)
{
unsigned maj, min, offset;
- dev_t devt = 0;
char *p, dummy;

if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2 ||
sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset, &dummy) == 3) {
- devt = MKDEV(maj, min);
- if (maj != MAJOR(devt) || min != MINOR(devt))
- return 0;
+ *devt = MKDEV(maj, min);
+ if (maj != MAJOR(*devt) || min != MINOR(*devt))
+ return -EINVAL;
} else {
- devt = new_decode_dev(simple_strtoul(name, &p, 16));
+ *devt = new_decode_dev(simple_strtoul(name, &p, 16));
if (*p)
- return 0;
+ return -EINVAL;
}

- return devt;
+ return 0;
}

/*
@@ -271,19 +268,18 @@ static dev_t devt_from_devnum(const char *name)
* name contains slashes, the device name has them replaced with
* bangs.
*/
-dev_t name_to_dev_t(const char *name)
+int early_lookup_bdev(const char *name, dev_t *devt)
{
-#ifdef CONFIG_BLOCK
if (strncmp(name, "PARTUUID=", 9) == 0)
- return devt_from_partuuid(name + 9);
+ return devt_from_partuuid(name + 9, devt);
if (strncmp(name, "PARTLABEL=", 10) == 0)
- return devt_from_partlabel(name + 10);
+ return devt_from_partlabel(name + 10, devt);
if (strncmp(name, "/dev/", 5) == 0)
- return devt_from_devname(name + 5);
-#endif
- return devt_from_devnum(name);
+ return devt_from_devname(name + 5, devt);
+ return devt_from_devnum(name, devt);
}
-EXPORT_SYMBOL_GPL(name_to_dev_t);
+EXPORT_SYMBOL_GPL(early_lookup_bdev);
+#endif

static int __init root_dev_setup(char *line)
{
@@ -606,20 +602,17 @@ static void __init wait_for_root(char *root_device_name)

pr_info("Waiting for root device %s...\n", root_device_name);

- for (;;) {
- if (driver_probe_done()) {
- ROOT_DEV = name_to_dev_t(root_device_name);
- if (ROOT_DEV)
- break;
- }
+ while (!driver_probe_done() ||
+ early_lookup_bdev(root_device_name, &ROOT_DEV) < 0)
msleep(5);
- }
async_synchronize_full();

}

static dev_t __init parse_root_device(char *root_device_name)
{
+ dev_t dev;
+
if (!strncmp(root_device_name, "mtd", 3) ||
!strncmp(root_device_name, "ubi", 3))
return Root_Generic;
@@ -629,7 +622,10 @@ static dev_t __init parse_root_device(char *root_device_name)
return Root_CIFS;
if (strcmp(root_device_name, "/dev/ram") == 0)
return Root_RAM0;
- return name_to_dev_t(root_device_name);
+
+ if (early_lookup_bdev(root_device_name, &dev))
+ return 0;
+ return dev;
}

/*
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 45e24b02cd50b6..c52dedb9f7c8e8 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -11,6 +11,7 @@

#define pr_fmt(fmt) "PM: hibernation: " fmt

+#include <linux/blkdev.h>
#include <linux/export.h>
#include <linux/suspend.h>
#include <linux/reboot.h>
@@ -921,8 +922,7 @@ static int __init find_resume_device(void)
}

/* Check if the device is there */
- swsusp_resume_device = name_to_dev_t(resume_file);
- if (swsusp_resume_device)
+ if (!early_lookup_bdev(resume_file, &swsusp_resume_device))
return 0;

/*
@@ -931,15 +931,12 @@ static int __init find_resume_device(void)
*/
wait_for_device_probe();
if (resume_wait) {
- while (!(swsusp_resume_device = name_to_dev_t(resume_file)))
+ while (early_lookup_bdev(resume_file, &swsusp_resume_device))
msleep(10);
async_synchronize_full();
}

- swsusp_resume_device = name_to_dev_t(resume_file);
- if (!swsusp_resume_device)
- return -ENODEV;
- return 0;
+ return early_lookup_bdev(resume_file, &swsusp_resume_device);
}

static int software_resume(void)
@@ -1169,7 +1166,8 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
unsigned int sleep_flags;
int len = n;
char *name;
- dev_t res;
+ dev_t dev;
+ int error;

if (!hibernation_available())
return 0;
@@ -1180,13 +1178,13 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
if (!name)
return -ENOMEM;

- res = name_to_dev_t(name);
+ error = early_lookup_bdev(name, &dev);
kfree(name);
- if (!res)
- return -EINVAL;
+ if (error)
+ return error;

sleep_flags = lock_system_sleep();
- swsusp_resume_device = res;
+ swsusp_resume_device = dev;
unlock_system_sleep(sleep_flags);

pm_pr_dbg("Configured hibernation resume from disk to %u\n",
--
2.39.2