Hi,
On Thu, Feb 02, 2017 at 06:34:02PM +0100, Jan Kara wrote:
> Provide helper functions for setting up dynamically allocated
> backing_dev_info structures for filesystems and cleaning them up on
> superblock destruction.
Just one concern, will this cause problems for multiple superblock cases
like nfs with nosharecache?
Thanks,
-liubo
>
> CC: linux-...@lists.infradead.org
> CC: linux-...@vger.kernel.org
> CC: Petr Vandrovec <p...@vandrovec.name>
> CC: linux-ni...@vger.kernel.org
> CC: cluster-de...@redhat.com
> CC: osd-...@open-osd.org
> CC: codal...@coda.cs.cmu.edu
> CC: linux-...@lists.infradead.org
> CC: ecryp...@vger.kernel.org
> CC: linux-c...@vger.kernel.org
> CC: ceph-de...@vger.kernel.org
> CC: linux-btrfs@vger.kernel.org
> CC: v9fs-develo...@lists.sourceforge.net
> CC: lustre-de...@lists.lustre.org
> Signed-off-by: Jan Kara <j...@suse.cz>
> ---
> fs/super.c | 49
> ++++++++++++++++++++++++++++++++++++++++
> include/linux/backing-dev-defs.h | 2 +-
> include/linux/fs.h | 6 +++++
> 3 files changed, 56 insertions(+), 1 deletion(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index ea662b0e5e78..31dc4c6450ef 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -446,6 +446,11 @@ void generic_shutdown_super(struct super_block *sb)
> hlist_del_init(&sb->s_instances);
> spin_unlock(&sb_lock);
> up_write(&sb->s_umount);
> + if (sb->s_iflags & SB_I_DYNBDI) {
> + bdi_put(sb->s_bdi);
> + sb->s_bdi = &noop_backing_dev_info;
> + sb->s_iflags &= ~SB_I_DYNBDI;
> + }
> }
>
> EXPORT_SYMBOL(generic_shutdown_super);
> @@ -1249,6 +1254,50 @@ mount_fs(struct file_system_type *type, int flags,
> const char *name, void *data)
> }
>
> /*
> + * Setup private BDI for given superblock. I gets automatically cleaned up
> + * in generic_shutdown_super().
> + */
> +int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
> +{
> + struct backing_dev_info *bdi;
> + int err;
> + va_list args;
> +
> + bdi = bdi_alloc(GFP_KERNEL);
> + if (!bdi)
> + return -ENOMEM;
> +
> + bdi->name = sb->s_type->name;
> +
> + va_start(args, fmt);
> + err = bdi_register_va(bdi, NULL, fmt, args);
> + va_end(args);
> + if (err) {
> + bdi_put(bdi);
> + return err;
> + }
> + WARN_ON(sb->s_bdi != &noop_backing_dev_info);
> + sb->s_bdi = bdi;
> + sb->s_iflags |= SB_I_DYNBDI;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(super_setup_bdi_name);
> +
> +/*
> + * Setup private BDI for given superblock. I gets automatically cleaned up
> + * in generic_shutdown_super().
> + */
> +int super_setup_bdi(struct super_block *sb)
> +{
> + static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
> +
> + return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
> + atomic_long_inc_return(&bdi_seq));
> +}
> +EXPORT_SYMBOL(super_setup_bdi);
> +
> +/*
> * This is an internal function, please use sb_end_{write,pagefault,intwrite}
> * instead.
> */
> diff --git a/include/linux/backing-dev-defs.h
> b/include/linux/backing-dev-defs.h
> index 2ecafc8a2d06..70080b4217f4 100644
> --- a/include/linux/backing-dev-defs.h
> +++ b/include/linux/backing-dev-defs.h
> @@ -143,7 +143,7 @@ struct backing_dev_info {
> congested_fn *congested_fn; /* Function pointer if device is md/dm */
> void *congested_data; /* Pointer to aux data for congested func */
>
> - char *name;
> + const char *name;
>
> struct kref refcnt; /* Reference counter for the structure */
> unsigned int registered:1; /* Is bdi registered? */
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index c930cbc19342..8ed8b6d1bc54 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1267,6 +1267,9 @@ struct mm_struct;
> /* sb->s_iflags to limit user namespace mounts */
> #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */
>
> +/* Temporary flag until all filesystems are converted to dynamic bdis */
> +#define SB_I_DYNBDI 0x00000100
> +
> /* Possible states of 'frozen' field */
> enum {
> SB_UNFROZEN = 0, /* FS is unfrozen */
> @@ -2103,6 +2106,9 @@ extern int vfs_ustat(dev_t, struct kstatfs *);
> extern int freeze_super(struct super_block *super);
> extern int thaw_super(struct super_block *super);
> extern bool our_mnt(struct vfsmount *mnt);
> +extern __printf(2, 3)
> +int super_setup_bdi_name(struct super_block *sb, char *fmt, ...);
> +extern int super_setup_bdi(struct super_block *sb);
>
> extern int current_umask(void);
>
> --
> 2.10.2
>
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