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init: Support mounting root file systems over SMB 

Add a new virtual device named /dev/cifs (0xfe) to tell the kernel to
mount the root file system over the network by using SMB protocol.

cifs_root_data() will be responsible to retrieve the parsed
information of the new command-line option (cifsroot=) and then call
do_mount_root() with the appropriate mount options for cifs.ko.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paulo Alcantara (SUSE) 2019-10-01 14:10:27 -03:00 committed by David S. Miller
parent 1f6d768a09
commit 8902dd5260
1 changed files with 49 additions and 0 deletions
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49
init/do_mounts.c
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@ -212,6 +212,7 @@ static int match_dev_by_label(struct device *dev, const void *data)
* a colon.
* 9) PARTLABEL=<name> with name being the GPT partition label.
* MSDOS partitions do not support labels!
* 10) /dev/cifs represents Root_CIFS (0xfe)
*
* If name doesn't have fall into the categories above, we return (0,0).
* block_class is used to check if something is a disk name. If the disk
@ -268,6 +269,9 @@ dev_t name_to_dev_t(const char *name)
res = Root_NFS;
if (strcmp(name, "nfs") == 0)
goto done;
res = Root_CIFS;
if (strcmp(name, "cifs") == 0)
goto done;
res = Root_RAM0;
if (strcmp(name, "ram") == 0)
goto done;
@ -501,6 +505,42 @@ static int __init mount_nfs_root(void)
}
#endif
#ifdef CONFIG_CIFS_ROOT
extern int cifs_root_data(char **dev, char **opts);
#define CIFSROOT_TIMEOUT_MIN 5
#define CIFSROOT_TIMEOUT_MAX 30
#define CIFSROOT_RETRY_MAX 5
static int __init mount_cifs_root(void)
{
char *root_dev, *root_data;
unsigned int timeout;
int try, err;
err = cifs_root_data(&root_dev, &root_data);
if (err != 0)
return 0;
timeout = CIFSROOT_TIMEOUT_MIN;
for (try = 1; ; try++) {
err = do_mount_root(root_dev, "cifs", root_mountflags,
root_data);
if (err == 0)
return 1;
if (try > CIFSROOT_RETRY_MAX)
break;
ssleep(timeout);
timeout <<= 1;
if (timeout > CIFSROOT_TIMEOUT_MAX)
timeout = CIFSROOT_TIMEOUT_MAX;
}
return 0;
}
#endif
#if defined(CONFIG_BLK_DEV_RAM) || defined(CONFIG_BLK_DEV_FD)
void __init change_floppy(char *fmt, ...)
{
@ -542,6 +582,15 @@ void __init mount_root(void)
ROOT_DEV = Root_FD0;
}
#endif
#ifdef CONFIG_CIFS_ROOT
if (ROOT_DEV == Root_CIFS) {
if (mount_cifs_root())
return;
printk(KERN_ERR "VFS: Unable to mount root fs via SMB, trying floppy.\n");
ROOT_DEV = Root_FD0;
}
#endif
#ifdef CONFIG_BLK_DEV_FD
if (MAJOR(ROOT_DEV) == FLOPPY_MAJOR) {
/* rd_doload is 2 for a dual initrd/ramload setup */