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![Dan Williams](/assets/img/avatar_default.png)
For configurations that do not enable DAX filesystems or drivers, do not require the DAX core to be built. Given that the 'direct_access' method has been removed from 'block_device_operations', we can also go ahead and remove the block-related dax helper functions from fs/block_dev.c to drivers/dax/super.c. This keeps dax details out of the block layer and lets the DAX core be built as a module in the FS_DAX=n case. Filesystems need to include dax.h to call bdev_dax_supported(). Cc: linux-xfs@vger.kernel.org Cc: Jens Axboe <axboe@kernel.dk> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Reviewed-by: Jan Kara <jack@suse.com> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
495 lines
11 KiB
C
495 lines
11 KiB
C
/*
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* Copyright(c) 2017 Intel Corporation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/pagemap.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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#include <linux/magic.h>
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#include <linux/genhd.h>
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#include <linux/cdev.h>
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#include <linux/hash.h>
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#include <linux/slab.h>
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#include <linux/dax.h>
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#include <linux/fs.h>
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static int nr_dax = CONFIG_NR_DEV_DAX;
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module_param(nr_dax, int, S_IRUGO);
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MODULE_PARM_DESC(nr_dax, "max number of dax device instances");
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static dev_t dax_devt;
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DEFINE_STATIC_SRCU(dax_srcu);
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static struct vfsmount *dax_mnt;
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static DEFINE_IDA(dax_minor_ida);
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static struct kmem_cache *dax_cache __read_mostly;
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static struct super_block *dax_superblock __read_mostly;
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#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
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static struct hlist_head dax_host_list[DAX_HASH_SIZE];
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static DEFINE_SPINLOCK(dax_host_lock);
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int dax_read_lock(void)
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{
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return srcu_read_lock(&dax_srcu);
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}
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EXPORT_SYMBOL_GPL(dax_read_lock);
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void dax_read_unlock(int id)
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{
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srcu_read_unlock(&dax_srcu, id);
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}
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EXPORT_SYMBOL_GPL(dax_read_unlock);
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int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
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pgoff_t *pgoff)
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{
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phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512;
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if (pgoff)
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*pgoff = PHYS_PFN(phys_off);
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if (phys_off % PAGE_SIZE || size % PAGE_SIZE)
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return -EINVAL;
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return 0;
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}
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EXPORT_SYMBOL(bdev_dax_pgoff);
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/**
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* __bdev_dax_supported() - Check if the device supports dax for filesystem
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* @sb: The superblock of the device
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* @blocksize: The block size of the device
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*
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* This is a library function for filesystems to check if the block device
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* can be mounted with dax option.
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*
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* Return: negative errno if unsupported, 0 if supported.
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*/
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int __bdev_dax_supported(struct super_block *sb, int blocksize)
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{
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struct block_device *bdev = sb->s_bdev;
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struct dax_device *dax_dev;
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pgoff_t pgoff;
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int err, id;
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void *kaddr;
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pfn_t pfn;
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long len;
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if (blocksize != PAGE_SIZE) {
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pr_err("VFS (%s): error: unsupported blocksize for dax\n",
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sb->s_id);
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return -EINVAL;
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}
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err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
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if (err) {
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pr_err("VFS (%s): error: unaligned partition for dax\n",
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sb->s_id);
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return err;
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}
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dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
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if (!dax_dev) {
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pr_err("VFS (%s): error: device does not support dax\n",
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sb->s_id);
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return -EOPNOTSUPP;
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}
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id = dax_read_lock();
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len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
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dax_read_unlock(id);
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put_dax(dax_dev);
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if (len < 1) {
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pr_err("VFS (%s): error: dax access failed (%ld)",
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sb->s_id, len);
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return len < 0 ? len : -EIO;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(__bdev_dax_supported);
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/**
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* struct dax_device - anchor object for dax services
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* @inode: core vfs
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* @cdev: optional character interface for "device dax"
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* @host: optional name for lookups where the device path is not available
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* @private: dax driver private data
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* @alive: !alive + rcu grace period == no new operations / mappings
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*/
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struct dax_device {
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struct hlist_node list;
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struct inode inode;
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struct cdev cdev;
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const char *host;
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void *private;
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bool alive;
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const struct dax_operations *ops;
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};
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/**
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* dax_direct_access() - translate a device pgoff to an absolute pfn
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* @dax_dev: a dax_device instance representing the logical memory range
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* @pgoff: offset in pages from the start of the device to translate
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* @nr_pages: number of consecutive pages caller can handle relative to @pfn
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* @kaddr: output parameter that returns a virtual address mapping of pfn
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* @pfn: output parameter that returns an absolute pfn translation of @pgoff
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*
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* Return: negative errno if an error occurs, otherwise the number of
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* pages accessible at the device relative @pgoff.
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*/
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long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
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void **kaddr, pfn_t *pfn)
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{
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long avail;
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/*
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* The device driver is allowed to sleep, in order to make the
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* memory directly accessible.
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*/
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might_sleep();
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if (!dax_dev)
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return -EOPNOTSUPP;
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if (!dax_alive(dax_dev))
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return -ENXIO;
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if (nr_pages < 0)
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return nr_pages;
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avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
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kaddr, pfn);
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if (!avail)
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return -ERANGE;
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return min(avail, nr_pages);
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}
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EXPORT_SYMBOL_GPL(dax_direct_access);
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bool dax_alive(struct dax_device *dax_dev)
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{
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lockdep_assert_held(&dax_srcu);
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return dax_dev->alive;
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}
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EXPORT_SYMBOL_GPL(dax_alive);
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static int dax_host_hash(const char *host)
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{
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return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
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}
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/*
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* Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
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* that any fault handlers or operations that might have seen
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* dax_alive(), have completed. Any operations that start after
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* synchronize_srcu() has run will abort upon seeing !dax_alive().
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*/
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void kill_dax(struct dax_device *dax_dev)
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{
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if (!dax_dev)
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return;
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dax_dev->alive = false;
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synchronize_srcu(&dax_srcu);
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spin_lock(&dax_host_lock);
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hlist_del_init(&dax_dev->list);
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spin_unlock(&dax_host_lock);
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dax_dev->private = NULL;
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}
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EXPORT_SYMBOL_GPL(kill_dax);
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static struct inode *dax_alloc_inode(struct super_block *sb)
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{
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struct dax_device *dax_dev;
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dax_dev = kmem_cache_alloc(dax_cache, GFP_KERNEL);
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return &dax_dev->inode;
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}
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static struct dax_device *to_dax_dev(struct inode *inode)
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{
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return container_of(inode, struct dax_device, inode);
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}
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static void dax_i_callback(struct rcu_head *head)
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{
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struct inode *inode = container_of(head, struct inode, i_rcu);
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struct dax_device *dax_dev = to_dax_dev(inode);
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kfree(dax_dev->host);
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dax_dev->host = NULL;
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ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
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kmem_cache_free(dax_cache, dax_dev);
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}
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static void dax_destroy_inode(struct inode *inode)
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{
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struct dax_device *dax_dev = to_dax_dev(inode);
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WARN_ONCE(dax_dev->alive,
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"kill_dax() must be called before final iput()\n");
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call_rcu(&inode->i_rcu, dax_i_callback);
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}
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static const struct super_operations dax_sops = {
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.statfs = simple_statfs,
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.alloc_inode = dax_alloc_inode,
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.destroy_inode = dax_destroy_inode,
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.drop_inode = generic_delete_inode,
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};
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static struct dentry *dax_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data)
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{
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return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
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}
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static struct file_system_type dax_fs_type = {
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.name = "dax",
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.mount = dax_mount,
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.kill_sb = kill_anon_super,
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};
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static int dax_test(struct inode *inode, void *data)
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{
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dev_t devt = *(dev_t *) data;
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return inode->i_rdev == devt;
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}
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static int dax_set(struct inode *inode, void *data)
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{
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dev_t devt = *(dev_t *) data;
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inode->i_rdev = devt;
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return 0;
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}
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static struct dax_device *dax_dev_get(dev_t devt)
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{
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struct dax_device *dax_dev;
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struct inode *inode;
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inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
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dax_test, dax_set, &devt);
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if (!inode)
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return NULL;
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dax_dev = to_dax_dev(inode);
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if (inode->i_state & I_NEW) {
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dax_dev->alive = true;
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inode->i_cdev = &dax_dev->cdev;
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inode->i_mode = S_IFCHR;
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inode->i_flags = S_DAX;
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mapping_set_gfp_mask(&inode->i_data, GFP_USER);
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unlock_new_inode(inode);
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}
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return dax_dev;
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}
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static void dax_add_host(struct dax_device *dax_dev, const char *host)
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{
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int hash;
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/*
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* Unconditionally init dax_dev since it's coming from a
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* non-zeroed slab cache
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*/
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INIT_HLIST_NODE(&dax_dev->list);
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dax_dev->host = host;
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if (!host)
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return;
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hash = dax_host_hash(host);
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spin_lock(&dax_host_lock);
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hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
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spin_unlock(&dax_host_lock);
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}
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struct dax_device *alloc_dax(void *private, const char *__host,
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const struct dax_operations *ops)
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{
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struct dax_device *dax_dev;
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const char *host;
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dev_t devt;
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int minor;
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host = kstrdup(__host, GFP_KERNEL);
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if (__host && !host)
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return NULL;
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minor = ida_simple_get(&dax_minor_ida, 0, nr_dax, GFP_KERNEL);
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if (minor < 0)
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goto err_minor;
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devt = MKDEV(MAJOR(dax_devt), minor);
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dax_dev = dax_dev_get(devt);
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if (!dax_dev)
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goto err_dev;
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dax_add_host(dax_dev, host);
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dax_dev->ops = ops;
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dax_dev->private = private;
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return dax_dev;
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err_dev:
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ida_simple_remove(&dax_minor_ida, minor);
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err_minor:
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kfree(host);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(alloc_dax);
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void put_dax(struct dax_device *dax_dev)
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{
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if (!dax_dev)
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return;
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iput(&dax_dev->inode);
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}
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EXPORT_SYMBOL_GPL(put_dax);
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/**
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* dax_get_by_host() - temporary lookup mechanism for filesystem-dax
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* @host: alternate name for the device registered by a dax driver
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*/
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struct dax_device *dax_get_by_host(const char *host)
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{
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struct dax_device *dax_dev, *found = NULL;
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int hash, id;
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if (!host)
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return NULL;
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hash = dax_host_hash(host);
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id = dax_read_lock();
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spin_lock(&dax_host_lock);
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hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
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if (!dax_alive(dax_dev)
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|| strcmp(host, dax_dev->host) != 0)
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continue;
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if (igrab(&dax_dev->inode))
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found = dax_dev;
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break;
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}
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spin_unlock(&dax_host_lock);
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dax_read_unlock(id);
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return found;
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}
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EXPORT_SYMBOL_GPL(dax_get_by_host);
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/**
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* inode_dax: convert a public inode into its dax_dev
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* @inode: An inode with i_cdev pointing to a dax_dev
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*
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* Note this is not equivalent to to_dax_dev() which is for private
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* internal use where we know the inode filesystem type == dax_fs_type.
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*/
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struct dax_device *inode_dax(struct inode *inode)
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{
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struct cdev *cdev = inode->i_cdev;
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return container_of(cdev, struct dax_device, cdev);
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}
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EXPORT_SYMBOL_GPL(inode_dax);
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struct inode *dax_inode(struct dax_device *dax_dev)
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{
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return &dax_dev->inode;
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}
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EXPORT_SYMBOL_GPL(dax_inode);
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void *dax_get_private(struct dax_device *dax_dev)
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{
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return dax_dev->private;
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}
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EXPORT_SYMBOL_GPL(dax_get_private);
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static void init_once(void *_dax_dev)
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{
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struct dax_device *dax_dev = _dax_dev;
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struct inode *inode = &dax_dev->inode;
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inode_init_once(inode);
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}
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static int __dax_fs_init(void)
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{
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int rc;
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dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
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(SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
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SLAB_MEM_SPREAD|SLAB_ACCOUNT),
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init_once);
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if (!dax_cache)
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return -ENOMEM;
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rc = register_filesystem(&dax_fs_type);
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if (rc)
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goto err_register_fs;
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dax_mnt = kern_mount(&dax_fs_type);
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if (IS_ERR(dax_mnt)) {
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rc = PTR_ERR(dax_mnt);
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goto err_mount;
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}
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dax_superblock = dax_mnt->mnt_sb;
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return 0;
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err_mount:
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unregister_filesystem(&dax_fs_type);
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err_register_fs:
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kmem_cache_destroy(dax_cache);
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return rc;
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}
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static void __dax_fs_exit(void)
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{
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kern_unmount(dax_mnt);
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unregister_filesystem(&dax_fs_type);
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kmem_cache_destroy(dax_cache);
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}
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static int __init dax_fs_init(void)
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{
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int rc;
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rc = __dax_fs_init();
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if (rc)
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return rc;
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nr_dax = max(nr_dax, 256);
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rc = alloc_chrdev_region(&dax_devt, 0, nr_dax, "dax");
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if (rc)
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__dax_fs_exit();
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return rc;
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}
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static void __exit dax_fs_exit(void)
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{
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unregister_chrdev_region(dax_devt, nr_dax);
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ida_destroy(&dax_minor_ida);
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__dax_fs_exit();
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}
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MODULE_AUTHOR("Intel Corporation");
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MODULE_LICENSE("GPL v2");
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subsys_initcall(dax_fs_init);
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module_exit(dax_fs_exit);
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