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    Subject[PATCH 08/19] fuse: Keep a list of free dax memory ranges
    Date
    Divide the dax memory range into fixed size ranges (2MB for now) and put
    them in a list. This will track free ranges. Once an inode requires a
    free range, we will take one from here and put it in interval-tree
    of ranges assigned to inode.

    Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
    Signed-off-by: Peng Tao <tao.peng@linux.alibaba.com>
    ---
    fs/fuse/fuse_i.h | 23 ++++++++++++
    fs/fuse/inode.c | 86 +++++++++++++++++++++++++++++++++++++++++++++
    fs/fuse/virtio_fs.c | 2 ++
    3 files changed, 111 insertions(+)

    diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
    index 7b365a29b156..f1059b51c539 100644
    --- a/fs/fuse/fuse_i.h
    +++ b/fs/fuse/fuse_i.h
    @@ -50,6 +50,10 @@
    /** Number of page pointers embedded in fuse_req */
    #define FUSE_REQ_INLINE_PAGES 1

    +/* Default memory range size, 2MB */
    +#define FUSE_DAX_MEM_RANGE_SZ (2*1024*1024)
    +#define FUSE_DAX_MEM_RANGE_PAGES (FUSE_DAX_MEM_RANGE_SZ/PAGE_SIZE)
    +
    /** List of active connections */
    extern struct list_head fuse_conn_list;

    @@ -97,6 +101,18 @@ struct fuse_forget_link {
    struct fuse_forget_link *next;
    };

    +/** Translation information for file offsets to DAX window offsets */
    +struct fuse_dax_mapping {
    + /* Will connect in fc->free_ranges to keep track of free memory */
    + struct list_head list;
    +
    + /** Position in DAX window */
    + u64 window_offset;
    +
    + /** Length of mapping, in bytes */
    + loff_t length;
    +};
    +
    /** FUSE inode */
    struct fuse_inode {
    /** Inode data */
    @@ -838,6 +854,13 @@ struct fuse_conn {

    /** DAX device, non-NULL if DAX is supported */
    struct dax_device *dax_dev;
    +
    + /*
    + * DAX Window Free Ranges. TODO: This might not be best place to store
    + * this free list
    + */
    + long nr_free_ranges;
    + struct list_head free_ranges;
    };

    static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
    diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
    index 0f58107a8269..0af147c70558 100644
    --- a/fs/fuse/inode.c
    +++ b/fs/fuse/inode.c
    @@ -22,6 +22,8 @@
    #include <linux/exportfs.h>
    #include <linux/posix_acl.h>
    #include <linux/pid_namespace.h>
    +#include <linux/dax.h>
    +#include <linux/pfn_t.h>

    MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
    MODULE_DESCRIPTION("Filesystem in Userspace");
    @@ -598,6 +600,76 @@ static void fuse_pqueue_init(struct fuse_pqueue *fpq)
    fpq->connected = 1;
    }

    +static void fuse_free_dax_mem_ranges(struct list_head *mem_list)
    +{
    + struct fuse_dax_mapping *range, *temp;
    +
    + /* Free All allocated elements */
    + list_for_each_entry_safe(range, temp, mem_list, list) {
    + list_del(&range->list);
    + kfree(range);
    + }
    +}
    +
    +#ifdef CONFIG_FS_DAX
    +static int fuse_dax_mem_range_init(struct fuse_conn *fc,
    + struct dax_device *dax_dev)
    +{
    + long nr_pages, nr_ranges;
    + void *kaddr;
    + pfn_t pfn;
    + struct fuse_dax_mapping *range;
    + LIST_HEAD(mem_ranges);
    + phys_addr_t phys_addr;
    + int ret = 0, id;
    + size_t dax_size = -1;
    + unsigned long i;
    +
    + id = dax_read_lock();
    + nr_pages = dax_direct_access(dax_dev, 0, PHYS_PFN(dax_size), &kaddr,
    + &pfn);
    + dax_read_unlock(id);
    + if (nr_pages < 0) {
    + pr_debug("dax_direct_access() returned %ld\n", nr_pages);
    + return nr_pages;
    + }
    +
    + phys_addr = pfn_t_to_phys(pfn);
    + nr_ranges = nr_pages/FUSE_DAX_MEM_RANGE_PAGES;
    + printk("fuse_dax_mem_range_init(): dax mapped %ld pages. nr_ranges=%ld\n", nr_pages, nr_ranges);
    +
    + for (i = 0; i < nr_ranges; i++) {
    + range = kzalloc(sizeof(struct fuse_dax_mapping), GFP_KERNEL);
    + if (!range) {
    + pr_debug("memory allocation for mem_range failed.\n");
    + ret = -ENOMEM;
    + goto out_err;
    + }
    + /* TODO: This offset only works if virtio-fs driver is not
    + * having some memory hidden at the beginning. This needs
    + * better handling
    + */
    + range->window_offset = i * FUSE_DAX_MEM_RANGE_SZ;
    + range->length = FUSE_DAX_MEM_RANGE_SZ;
    + list_add_tail(&range->list, &mem_ranges);
    + }
    +
    + list_replace_init(&mem_ranges, &fc->free_ranges);
    + fc->nr_free_ranges = nr_ranges;
    + return 0;
    +out_err:
    + /* Free All allocated elements */
    + fuse_free_dax_mem_ranges(&mem_ranges);
    + return ret;
    +}
    +#else /* !CONFIG_FS_DAX */
    +static inline int fuse_dax_mem_range_init(struct fuse_conn *fc,
    + struct dax_device *dax_dev)
    +{
    + return 0;
    +}
    +#endif /* CONFIG_FS_DAX */
    +
    void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
    struct dax_device *dax_dev,
    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv)
    @@ -628,6 +700,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
    fc->dax_dev = dax_dev;
    fc->user_ns = get_user_ns(user_ns);
    fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ;
    + INIT_LIST_HEAD(&fc->free_ranges);
    }
    EXPORT_SYMBOL_GPL(fuse_conn_init);

    @@ -636,6 +709,8 @@ void fuse_conn_put(struct fuse_conn *fc)
    if (refcount_dec_and_test(&fc->count)) {
    if (fc->destroy_req)
    fuse_request_free(fc->destroy_req);
    + if (fc->dax_dev)
    + fuse_free_dax_mem_ranges(&fc->free_ranges);
    put_pid_ns(fc->pid_ns);
    put_user_ns(fc->user_ns);
    fc->release(fc);
    @@ -1147,6 +1222,14 @@ int fuse_fill_super_common(struct super_block *sb,
    fc->release = fuse_free_conn;
    }

    + if (mount_data->dax_dev) {
    + err = fuse_dax_mem_range_init(fc, mount_data->dax_dev);
    + if (err) {
    + pr_debug("fuse_dax_mem_range_init() returned %d\n", err);
    + goto err_free_ranges;
    + }
    + }
    +
    fud = fuse_dev_alloc_install(fc);
    if (!fud)
    goto err_put_conn;
    @@ -1208,6 +1291,9 @@ int fuse_fill_super_common(struct super_block *sb,
    dput(root_dentry);
    err_dev_free:
    fuse_dev_free(fud);
    + err_free_ranges:
    + if (mount_data->dax_dev)
    + fuse_free_dax_mem_ranges(&fc->free_ranges);
    err_put_conn:
    fuse_conn_put(fc);
    sb->s_fs_info = NULL;
    diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
    index 32604722a7fb..9198c2b84677 100644
    --- a/fs/fuse/virtio_fs.c
    +++ b/fs/fuse/virtio_fs.c
    @@ -453,6 +453,8 @@ static long virtio_fs_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
    phys_addr_t offset = PFN_PHYS(pgoff);
    size_t max_nr_pages = fs->window_len/PAGE_SIZE - pgoff;

    + pr_debug("virtio_fs_direct_access(): called. nr_pages=%ld max_nr_pages=%zu\n", nr_pages, max_nr_pages);
    +
    if (kaddr)
    *kaddr = fs->window_kaddr + offset;
    if (pfn)
    --
    2.20.1
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