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ubifs: add option to specify version for new file systems

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Instead of creating ubifs file systems with UBIFS_FORMAT_VERSION
by default, add a module parameter ubifs.default_version to allow
the user to specify the desired version. Valid values are 4 to
UBIFS_FORMAT_VERSION (currently 5).

This way, one can for example create a file system with version 4
on kernel 4.19 which can still be mounted rw when downgrading to
kernel 4.9.

Signed-off-by: Martin Kaistra <martin.kaistra@linutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Martin Kaistra 2020-07-07 12:31:59 +02:00 committed by Richard Weinberger
parent 92ed301919
commit a7a8f4a1e6
3 changed files with 22 additions and 2 deletions
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5
fs/ubifs/sb.c
View File

@ -174,7 +174,8 @@ static int create_default_filesystem(struct ubifs_info *c)
tmp64 = (long long)max_buds * c->leb_size;
if (big_lpt)
sup_flags |= UBIFS_FLG_BIGLPT;
sup_flags |= UBIFS_FLG_DOUBLE_HASH;
if (ubifs_default_version > 4)
sup_flags |= UBIFS_FLG_DOUBLE_HASH;
if (ubifs_authenticated(c)) {
sup_flags |= UBIFS_FLG_AUTHENTICATION;
@ -200,7 +201,7 @@ static int create_default_filesystem(struct ubifs_info *c)
sup->jhead_cnt = cpu_to_le32(DEFAULT_JHEADS_CNT);
sup->fanout = cpu_to_le32(DEFAULT_FANOUT);
sup->lsave_cnt = cpu_to_le32(c->lsave_cnt);
sup->fmt_version = cpu_to_le32(UBIFS_FORMAT_VERSION);
sup->fmt_version = cpu_to_le32(ubifs_default_version);
sup->time_gran = cpu_to_le32(DEFAULT_TIME_GRAN);
if (c->mount_opts.override_compr)
sup->default_compr = cpu_to_le16(c->mount_opts.compr_type);

18
fs/ubifs/super.c
View File

@ -26,6 +26,24 @@
#include <linux/writeback.h>
#include "ubifs.h"
static int ubifs_default_version_set(const char *val, const struct kernel_param *kp)
{
int n = 0, ret;
ret = kstrtoint(val, 10, &n);
if (ret != 0 || n < 4 || n > UBIFS_FORMAT_VERSION)
return -EINVAL;
return param_set_int(val, kp);
}
static const struct kernel_param_ops ubifs_default_version_ops = {
.set = ubifs_default_version_set,
.get = param_get_int,
};
int ubifs_default_version = UBIFS_FORMAT_VERSION;
module_param_cb(default_version, &ubifs_default_version_ops, &ubifs_default_version, 0600);
/*
* Maximum amount of memory we may 'kmalloc()' without worrying that we are
* allocating too much.

1
fs/ubifs/ubifs.h
View File

@ -1504,6 +1504,7 @@ extern const struct file_operations ubifs_dir_operations;
extern const struct inode_operations ubifs_dir_inode_operations;
extern const struct inode_operations ubifs_symlink_inode_operations;
extern struct ubifs_compressor *ubifs_compressors[UBIFS_COMPR_TYPES_CNT];
extern int ubifs_default_version;
/* auth.c */
static inline int ubifs_authenticated(const struct ubifs_info *c)