Provide a function, vfs_get_mtd_super(), to replace mount_mtd(), using an fs_context struct to hold the parameters. The mtd device pointer is cached in the struct, along with a destructor pointer as the mtd core may be in a module and, as such, unreachable by the core code that would release the fs_context.
Signed-off-by: David Howells <[email protected]> cc: David Woodhouse <[email protected]> cc: Brian Norris <[email protected]> cc: Boris Brezillon <[email protected]> cc: Marek Vasut <[email protected]> cc: Richard Weinberger <[email protected]> cc: [email protected] --- drivers/mtd/mtdcore.h | 1 drivers/mtd/mtdsuper.c | 192 ++++++++++++++++++++++++++++++++++++++++++++ fs/fs_context.c | 2 include/linux/fs_context.h | 2 include/linux/mtd/super.h | 3 + 5 files changed, 198 insertions(+), 2 deletions(-) diff --git a/drivers/mtd/mtdcore.h b/drivers/mtd/mtdcore.h index b31c868019ad..b5eefeabf310 100644 --- a/drivers/mtd/mtdcore.h +++ b/drivers/mtd/mtdcore.h @@ -5,6 +5,7 @@ */ extern struct mutex mtd_table_mutex; +extern struct backing_dev_info *mtd_bdi; struct mtd_info *__mtd_next_device(int i); int __must_check add_mtd_device(struct mtd_info *mtd); diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c index d58a61c09304..cf223c4aa862 100644 --- a/drivers/mtd/mtdsuper.c +++ b/drivers/mtd/mtdsuper.c @@ -19,6 +19,196 @@ #include <linux/slab.h> #include <linux/major.h> #include <linux/backing-dev.h> +#include <linux/fs_context.h> +#include "mtdcore.h" + +static void mtd_fc_destructor(struct fs_context *fc) +{ + if (fc->mtd) + put_mtd_device(fc->mtd); +} + +/* + * compare superblocks to see if they're equivalent + * - they are if the underlying MTD device is the same + */ +static int mtd_test_super(struct super_block *sb, struct fs_context *fc) +{ + struct mtd_info *mtd = fc->mtd; + + if (sb->s_mtd == mtd) { + pr_debug("MTDSB: Match on device %d (\"%s\")\n", + mtd->index, mtd->name); + return 1; + } + + pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n", + sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name); + return 0; +} + +/* + * mark the superblock by the MTD device it is using + * - set the device number to be the correct MTD block device for pesuperstence + * of NFS exports + */ +static int mtd_set_super(struct super_block *sb, struct fs_context *fc) +{ + struct mtd_info *mtd = fc->mtd; + + sb->s_mtd = mtd; + sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index); + sb->s_bdi = bdi_get(mtd_bdi); + fc->mtd = NULL; + return 0; +} + +/* + * get a superblock on an MTD-backed filesystem + */ +static int mtd_get_sb(struct fs_context *fc, + int (*fill_super)(struct super_block *, + struct fs_context *)) +{ + struct super_block *sb; + struct mtd_info *mtd = fc->mtd; + int ret; + + sb = sget_fc(fc, mtd_test_super, mtd_set_super); + if (IS_ERR(sb)) + return PTR_ERR(sb); + + if (sb->s_root) { + /* new mountpoint for an already mounted superblock */ + pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n", + mtd->index, mtd->name); + put_mtd_device(mtd); + } else { + /* fresh new superblock */ + pr_debug("MTDSB: New superblock for device %d (\"%s\")\n", + mtd->index, mtd->name); + + ret = fill_super(sb, fc); + if (ret < 0) + goto error_sb; + + sb->s_flags |= SB_ACTIVE; + } + + BUG_ON(fc->root); + fc->root = dget(sb->s_root); + return 0; + +error_sb: + deactivate_locked_super(sb); + return ret; +} + +/* + * get a superblock on an MTD-backed filesystem by MTD device number + */ +static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr, + int (*fill_super)(struct super_block *, + struct fs_context *)) +{ + struct mtd_info *mtd; + + mtd = get_mtd_device(NULL, mtdnr); + if (IS_ERR(mtd)) { + errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr); + return PTR_ERR(mtd); + } + + fc->mtd = mtd; + fc->destructor = mtd_fc_destructor; + return mtd_get_sb(fc, fill_super); +} + +/** + * vfs_get_mtd_super - Get a superblock based on a single MTD device + * @fc: The filesystem context holding the parameters + * @fill_super: Helper to initialise a new superblock + */ +int vfs_get_mtd_super(struct fs_context *fc, + int (*fill_super)(struct super_block *sb, + struct fs_context *fc)) +{ +#ifdef CONFIG_BLOCK + struct block_device *bdev; + int ret, major; +#endif + int mtdnr; + + if (!fc->source) + return invalf(fc, "No source specified"); + + pr_debug("MTDSB: dev_name \"%s\"\n", fc->source); + + /* the preferred way of mounting in future; especially when + * CONFIG_BLOCK=n - we specify the underlying MTD device by number or + * by name, so that we don't require block device support to be present + * in the kernel. + */ + if (fc->source[0] == 'm' && + fc->source[1] == 't' && + fc->source[2] == 'd') { + if (fc->source[3] == ':') { + struct mtd_info *mtd; + + /* mount by MTD device name */ + pr_debug("MTDSB: mtd:%%s, name \"%s\"\n", + fc->source + 4); + + mtd = get_mtd_device_nm(fc->source + 4); + if (!IS_ERR(mtd)) { + fc->mtd = mtd; + fc->destructor = mtd_fc_destructor; + return mtd_get_sb(fc, fill_super); + } + + errorf(fc, "MTD: MTD device with name \"%s\" not found", + fc->source + 4); + + } else if (isdigit(fc->source[3])) { + /* mount by MTD device number name */ + char *endptr; + + mtdnr = simple_strtoul(fc->source + 3, &endptr, 0); + if (!*endptr) { + /* It was a valid number */ + pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr); + return mtd_get_sb_by_nr(fc, mtdnr, fill_super); + } + } + } + +#ifdef CONFIG_BLOCK + /* try the old way - the hack where we allowed users to mount + * /dev/mtdblock$(n) but didn't actually _use_ the blockdev + */ + bdev = lookup_bdev(fc->source); + if (IS_ERR(bdev)) { + ret = PTR_ERR(bdev); + errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret); + return ret; + } + pr_debug("MTDSB: lookup_bdev() returned 0\n"); + + major = MAJOR(bdev->bd_dev); + mtdnr = MINOR(bdev->bd_dev); + bdput(bdev); + + if (major == MTD_BLOCK_MAJOR) + return mtd_get_sb_by_nr(fc, mtdnr, fill_super); + +#endif /* CONFIG_BLOCK */ + + if (!(fc->sb_flags & SB_SILENT)) + errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"", + fc->source); + return -EINVAL; +} +EXPORT_SYMBOL_GPL(vfs_get_mtd_super); /* * compare superblocks to see if they're equivalent @@ -39,8 +229,6 @@ static int get_sb_mtd_compare(struct super_block *sb, void *_mtd) return 0; } -extern struct backing_dev_info *mtd_bdi; - /* * mark the superblock by the MTD device it is using * - set the device number to be the correct MTD block device for pesuperstence diff --git a/fs/fs_context.c b/fs/fs_context.c index 3325b435cb6f..65e705d02521 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -427,6 +427,8 @@ void put_fs_context(struct fs_context *fc) fc->ops->free(fc); if (fc->bdev) blkdev_put(fc->bdev, fc->bdev_mode); + if (fc->destructor) + fc->destructor(fc); security_free_mnt_opts(&fc->security); put_net(fc->net_ns); diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index 524963c0cedb..8233c873af73 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -77,6 +77,7 @@ struct fs_context { struct file_system_type *fs_type; void *fs_private; /* The filesystem's context */ struct block_device *bdev; /* The backing blockdev (if applicable) */ + struct mtd_info *mtd; /* The backing mtd (if applicable) */ struct dentry *root; /* The root and superblock */ struct user_namespace *user_ns; /* The user namespace for this mount */ struct net *net_ns; /* The network namespace for this mount */ @@ -92,6 +93,7 @@ struct fs_context { enum fs_context_purpose purpose:8; bool need_free:1; /* Need to call ops->free() */ bool global:1; /* Goes into &init_user_ns */ + void (*destructor)(struct fs_context *fc); /* For mtd */ }; struct fs_context_operations { diff --git a/include/linux/mtd/super.h b/include/linux/mtd/super.h index f456230f9330..7ebd69e5c640 100644 --- a/include/linux/mtd/super.h +++ b/include/linux/mtd/super.h @@ -18,6 +18,9 @@ #include <linux/fs.h> #include <linux/mount.h> +extern int vfs_get_mtd_super(struct fs_context *fc, + int (*fill_super)(struct super_block *sb, + struct fs_context *fc)); extern struct dentry *mount_mtd(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, int (*fill_super)(struct super_block *, void *, int));
