Re: [PATCH v13 1/7] dax: Introduce holder for dax_device

Darrick J. Wong
2022-04-20T17:42:31Z

On Tue, Apr 19, 2022 at 12:50:39PM +0800, Shiyang Ruan wrote:
> To easily track filesystem from a pmem device, we introduce a holder for
> dax_device structure, and also its operation. This holder is used to
> remember who is using this dax_device:
> - When it is the backend of a filesystem, the holder will be the
> instance of this filesystem.
> - When this pmem device is one of the targets in a mapped device, the
> holder will be this mapped device. In this case, the mapped device
> has its own dax_device and it will follow the first rule. So that we
> can finally track to the filesystem we needed.
>
> The holder and holder_ops will be set when filesystem is being mounted,
> or an target device is being activated.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Dan Williams <dan.j.wiliams@intel.com>

LGTM
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> drivers/dax/super.c | 67 ++++++++++++++++++++++++++++++++++++++++++++-
> drivers/md/dm.c | 2 +-
> fs/erofs/super.c | 10 ++++---
> fs/ext2/super.c | 7 +++--
> fs/ext4/super.c | 9 +++---
> fs/xfs/xfs_buf.c | 5 ++--
> include/linux/dax.h | 33 ++++++++++++++++------
> 7 files changed, 110 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 0211e6f7b47a..5ddb159c4653 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -22,6 +22,8 @@
> * @private: dax driver private data
> * @flags: state and boolean properties
> * @ops: operations for this device
> + * @holder_data: holder of a dax_device: could be filesystem or mapped device
> + * @holder_ops: operations for the inner holder
> */
> struct dax_device {
> struct inode inode;
> @@ -29,6 +31,8 @@ struct dax_device {
> void *private;
> unsigned long flags;
> const struct dax_operations *ops;
> + void *holder_data;
> + const struct dax_holder_operations *holder_ops;
> };
>
> static dev_t dax_devt;
> @@ -71,8 +75,11 @@ EXPORT_SYMBOL_GPL(dax_remove_host);
> * fs_dax_get_by_bdev() - temporary lookup mechanism for filesystem-dax
> * @bdev: block device to find a dax_device for
> * @start_off: returns the byte offset into the dax_device that @bdev starts
> + * @holder: filesystem or mapped device inside the dax_device
> + * @ops: operations for the inner holder
> */
> -struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off)
> +struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off,
> + void *holder, const struct dax_holder_operations *ops)
> {
> struct dax_device *dax_dev;
> u64 part_size;
> @@ -92,11 +99,26 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off)
> dax_dev = xa_load(&dax_hosts, (unsigned long)bdev->bd_disk);
> if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
> dax_dev = NULL;
> + else if (holder) {
> + if (!cmpxchg(&dax_dev->holder_data, NULL, holder))
> + dax_dev->holder_ops = ops;
> + else
> + dax_dev = NULL;
> + }
> dax_read_unlock(id);
>
> return dax_dev;
> }
> EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
> +
> +void fs_put_dax(struct dax_device *dax_dev, void *holder)
> +{
> + if (dax_dev && holder &&
> + cmpxchg(&dax_dev->holder_data, holder, NULL) == holder)
> + dax_dev->holder_ops = NULL;
> + put_dax(dax_dev);
> +}
> +EXPORT_SYMBOL_GPL(fs_put_dax);
> #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
>
> enum dax_device_flags {
> @@ -194,6 +216,29 @@ int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
> }
> EXPORT_SYMBOL_GPL(dax_zero_page_range);
>
> +int dax_holder_notify_failure(struct dax_device *dax_dev, u64 off,
> + u64 len, int mf_flags)
> +{
> + int rc, id;
> +
> + id = dax_read_lock();
> + if (!dax_alive(dax_dev)) {
> + rc = -ENXIO;
> + goto out;
> + }
> +
> + if (!dax_dev->holder_ops) {
> + rc = -EOPNOTSUPP;
> + goto out;
> + }
> +
> + rc = dax_dev->holder_ops->notify_failure(dax_dev, off, len, mf_flags);
> +out:
> + dax_read_unlock(id);
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(dax_holder_notify_failure);
> +
> #ifdef CONFIG_ARCH_HAS_PMEM_API
> void arch_wb_cache_pmem(void *addr, size_t size);
> void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
> @@ -267,8 +312,15 @@ void kill_dax(struct dax_device *dax_dev)
> if (!dax_dev)
> return;
>
> + if (dax_dev->holder_data != NULL)
> + dax_holder_notify_failure(dax_dev, 0, U64_MAX, 0);
> +
> clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
> synchronize_srcu(&dax_srcu);
> +
> + /* clear holder data */
> + dax_dev->holder_ops = NULL;
> + dax_dev->holder_data = NULL;
> }
> EXPORT_SYMBOL_GPL(kill_dax);
>
> @@ -410,6 +462,19 @@ void put_dax(struct dax_device *dax_dev)
> }
> EXPORT_SYMBOL_GPL(put_dax);
>
> +/**
> + * dax_holder() - obtain the holder of a dax device
> + * @dax_dev: a dax_device instance
> +
> + * Return: the holder's data which represents the holder if registered,
> + * otherwize NULL.
> + */
> +void *dax_holder(struct dax_device *dax_dev)
> +{
> + return dax_dev->holder_data;
> +}
> +EXPORT_SYMBOL_GPL(dax_holder);
> +
> /**
> * inode_dax: convert a public inode into its dax_dev
> * @inode: An inode with i_cdev pointing to a dax_dev
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 3c5fad7c4ee6..5906b4efc767 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -721,7 +721,7 @@ static int open_table_device(struct table_device *td, dev_t dev,
> }
>
> td->dm_dev.bdev = bdev;
> - td->dm_dev.dax_dev = fs_dax_get_by_bdev(bdev, &part_off);
> + td->dm_dev.dax_dev = fs_dax_get_by_bdev(bdev, &part_off, NULL, NULL);
> return 0;
> }
>
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 0c4b41130c2f..d0eab646ef94 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -267,7 +267,8 @@ static int erofs_init_devices(struct super_block *sb,
> break;
> }
> dif->bdev = bdev;
> - dif->dax_dev = fs_dax_get_by_bdev(bdev, &dif->dax_part_off);
> + dif->dax_dev = fs_dax_get_by_bdev(bdev, &dif->dax_part_off,
> + NULL, NULL);
> dif->blocks = le32_to_cpu(dis->blocks);
> dif->mapped_blkaddr = le32_to_cpu(dis->mapped_blkaddr);
> sbi->total_blocks += dif->blocks;
> @@ -597,7 +598,8 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>
> sb->s_fs_info = sbi;
> sbi->opt = ctx->opt;
> - sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->dax_part_off);
> + sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->dax_part_off,
> + NULL, NULL);
> sbi->devs = ctx->devs;
> ctx->devs = NULL;
>
> @@ -687,7 +689,7 @@ static int erofs_release_device_info(int id, void *ptr, void *data)
> {
> struct erofs_device_info *dif = ptr;
>
> - fs_put_dax(dif->dax_dev);
> + fs_put_dax(dif->dax_dev, NULL);
> if (dif->bdev)
> blkdev_put(dif->bdev, FMODE_READ | FMODE_EXCL);
> kfree(dif->path);
> @@ -756,7 +758,7 @@ static void erofs_kill_sb(struct super_block *sb)
> return;
>
> erofs_free_dev_context(sbi->devs);
> - fs_put_dax(sbi->dax_dev);
> + fs_put_dax(sbi->dax_dev, NULL);
> kfree(sbi);
> sb->s_fs_info = NULL;
> }
> diff --git a/fs/ext2/super.c b/fs/ext2/super.c
> index f6a19f6d9f6d..4638946251b9 100644
> --- a/fs/ext2/super.c
> +++ b/fs/ext2/super.c
> @@ -171,7 +171,7 @@ static void ext2_put_super (struct super_block * sb)
> brelse (sbi->s_sbh);
> sb->s_fs_info = NULL;
> kfree(sbi->s_blockgroup_lock);
> - fs_put_dax(sbi->s_daxdev);
> + fs_put_dax(sbi->s_daxdev, NULL);
> kfree(sbi);
> }
>
> @@ -835,7 +835,8 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
> }
> sb->s_fs_info = sbi;
> sbi->s_sb_block = sb_block;
> - sbi->s_daxdev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->s_dax_part_off);
> + sbi->s_daxdev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->s_dax_part_off,
> + NULL, NULL);
>
> spin_lock_init(&sbi->s_lock);
> ret = -EINVAL;
> @@ -1204,7 +1205,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
> failed_mount:
> brelse(bh);
> failed_sbi:
> - fs_put_dax(sbi->s_daxdev);
> + fs_put_dax(sbi->s_daxdev, NULL);
> sb->s_fs_info = NULL;
> kfree(sbi->s_blockgroup_lock);
> kfree(sbi);
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index f5f4f2606ab2..59d5b2e8f838 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1300,7 +1300,7 @@ static void ext4_put_super(struct super_block *sb)
> if (sbi->s_chksum_driver)
> crypto_free_shash(sbi->s_chksum_driver);
> kfree(sbi->s_blockgroup_lock);
> - fs_put_dax(sbi->s_daxdev);
> + fs_put_dax(sbi->s_daxdev, NULL);
> fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy);
> #if IS_ENABLED(CONFIG_UNICODE)
> utf8_unload(sb->s_encoding);
> @@ -4351,7 +4351,7 @@ static void ext4_free_sbi(struct ext4_sb_info *sbi)
> return;
>
> kfree(sbi->s_blockgroup_lock);
> - fs_put_dax(sbi->s_daxdev);
> + fs_put_dax(sbi->s_daxdev, NULL);
> kfree(sbi);
> }
>
> @@ -4363,7 +4363,8 @@ static struct ext4_sb_info *ext4_alloc_sbi(struct super_block *sb)
> if (!sbi)
> return NULL;
>
> - sbi->s_daxdev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->s_dax_part_off);
> + sbi->s_daxdev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->s_dax_part_off,
> + NULL, NULL);
>
> sbi->s_blockgroup_lock =
> kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
> @@ -4375,7 +4376,7 @@ static struct ext4_sb_info *ext4_alloc_sbi(struct super_block *sb)
> sbi->s_sb = sb;
> return sbi;
> err_out:
> - fs_put_dax(sbi->s_daxdev);
> + fs_put_dax(sbi->s_daxdev, NULL);
> kfree(sbi);
> return NULL;
> }
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index e1afb9e503e1..f9ca08398d32 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -1911,7 +1911,7 @@ xfs_free_buftarg(
> list_lru_destroy(&btp->bt_lru);
>
> blkdev_issue_flush(btp->bt_bdev);
> - fs_put_dax(btp->bt_daxdev);
> + fs_put_dax(btp->bt_daxdev, NULL);
>
> kmem_free(btp);
> }
> @@ -1964,7 +1964,8 @@ xfs_alloc_buftarg(
> btp->bt_mount = mp;
> btp->bt_dev = bdev->bd_dev;
> btp->bt_bdev = bdev;
> - btp->bt_daxdev = fs_dax_get_by_bdev(bdev, &btp->bt_dax_part_off);
> + btp->bt_daxdev = fs_dax_get_by_bdev(bdev, &btp->bt_dax_part_off, NULL,
> + NULL);
>
> /*
> * Buffer IO error rate limiting. Limit it to no more than 10 messages
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 9fc5f99a0ae2..9c426a207ba8 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -32,8 +32,21 @@ struct dax_operations {
> int (*zero_page_range)(struct dax_device *, pgoff_t, size_t);
> };
>
> +struct dax_holder_operations {
> + /*
> + * notify_failure - notify memory failure into inner holder device
> + * @dax_dev: the dax device which contains the holder
> + * @offset: offset on this dax device where memory failure occurs
> + * @len: length of this memory failure event
> + * @flags: action flags for memory failure handler
> + */
> + int (*notify_failure)(struct dax_device *dax_dev, u64 offset,
> + u64 len, int mf_flags);
> +};
> +
> #if IS_ENABLED(CONFIG_DAX)
> struct dax_device *alloc_dax(void *private, const struct dax_operations *ops);
> +void *dax_holder(struct dax_device *dax_dev);
> void put_dax(struct dax_device *dax_dev);
> void kill_dax(struct dax_device *dax_dev);
> void dax_write_cache(struct dax_device *dax_dev, bool wc);
> @@ -53,6 +66,10 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
> return dax_synchronous(dax_dev);
> }
> #else
> +static inline void *dax_holder(struct dax_device *dax_dev)
> +{
> + return NULL;
> +}
> static inline struct dax_device *alloc_dax(void *private,
> const struct dax_operations *ops)
> {
> @@ -96,12 +113,9 @@ struct writeback_control;
> #if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
> int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk);
> void dax_remove_host(struct gendisk *disk);
> -struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev,
> - u64 *start_off);
> -static inline void fs_put_dax(struct dax_device *dax_dev)
> -{
> - put_dax(dax_dev);
> -}
> +struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off,
> + void *holder, const struct dax_holder_operations *ops);
> +void fs_put_dax(struct dax_device *dax_dev, void *holder);
> #else
> static inline int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)
> {
> @@ -111,11 +125,12 @@ static inline void dax_remove_host(struct gendisk *disk)
> {
> }
> static inline struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev,
> - u64 *start_off)
> + u64 *start_off, void *holder,
> + const struct dax_holder_operations *ops)
> {
> return NULL;
> }
> -static inline void fs_put_dax(struct dax_device *dax_dev)
> +static inline void fs_put_dax(struct dax_device *dax_dev, void *holder)
> {
> }
> #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
> @@ -185,6 +200,8 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
> size_t bytes, struct iov_iter *i);
> int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
> size_t nr_pages);
> +int dax_holder_notify_failure(struct dax_device *dax_dev, u64 off, u64 len,
> + int mf_flags);
> void dax_flush(struct dax_device *dax_dev, void *addr, size_t size);
>
> ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
> --
> 2.35.1
>
>
>