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    SubjectRe: [-mm patch] relayfs: add read() support
    On Thu, Aug 04 2005, Tom Zanussi wrote:
    > At the kernel summit, there was some discussion of relayfs and the
    > consensus was that it didn't make sense for relayfs to not implement
    > read(). So here's a read implementation...

    It needs a few fixes to actually compile without errors. This works for
    me, just tested with the block tracing stuff, works a charm!


    diff -urp -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc4-mm1/fs/relayfs/inode.c linux-2.6.13-rc4-mm1/fs/relayfs/inode.c
    --- /opt/kernel/linux-2.6.13-rc4-mm1/fs/relayfs/inode.c 2005-08-05 16:47:57.000000000 +0200
    +++ linux-2.6.13-rc4-mm1/fs/relayfs/inode.c 2005-08-05 16:45:38.000000000 +0200
    @@ -33,6 +33,8 @@ static struct backing_dev_info relayfs_
    .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
    };

    +struct file_operations relayfs_file_operations;
    +
    static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
    struct rchan *chan)
    {
    @@ -370,7 +372,7 @@ static inline unsigned int relayfs_read_
    *
    */
    static inline unsigned int relayfs_read_avail(struct rchan_buf *buf,
    - unsigned int *start_subbuf)
    + size_t *start_subbuf)
    {
    unsigned int avail, complete_subbufs, cur_subbuf, buf_offset;
    unsigned int subbuf_size = buf->chan->subbuf_size;
    @@ -378,12 +380,12 @@ static inline unsigned int relayfs_read_

    buf_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;

    - if (buf->subbufs_produced >= n_subbufs) {
    + if (atomic_read(&buf->subbufs_produced) >= n_subbufs) {
    complete_subbufs = n_subbufs - 1;
    cur_subbuf = (buf->data - buf->start) / subbuf_size;
    *start_subbuf = (cur_subbuf + 1) % n_subbufs;
    } else {
    - complete_subbufs = buf->subbufs_produced;
    + complete_subbufs = atomic_read(&buf->subbufs_produced);
    *start_subbuf = 0;
    }

    @@ -416,8 +418,8 @@ static ssize_t relayfs_read(struct file
    {
    struct inode *inode = filp->f_dentry->d_inode;
    struct rchan_buf *buf = RELAYFS_I(inode)->buf;
    - unsigned int read_start, read_end, avail, start_subbuf;
    - unsigned int buf_size = buf->chan->subbuf_size * buf->chan->n_subbufs;
    + size_t read_start, read_end, avail, start_subbuf;
    + size_t buf_size = buf->chan->subbuf_size * buf->chan->n_subbufs;
    void *from;

    avail = relayfs_read_avail(buf, &start_subbuf);
    diff -urp -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc4-mm1/include/linux/relayfs_fs.h linux-2.6.13-rc4-mm1/include/linux/relayfs_fs.h
    --- /opt/kernel/linux-2.6.13-rc4-mm1/include/linux/relayfs_fs.h 2005-08-05 16:47:44.000000000 +0200
    +++ linux-2.6.13-rc4-mm1/include/linux/relayfs_fs.h 2005-08-05 16:45:47.000000000 +0200
    @@ -253,15 +253,5 @@ static inline void *relay_reserve(struct
    return reserved;
    }

    -/*
    - * exported relayfs file operations, fs/relayfs/inode.c
    - */
    -
    -extern struct file_operations relayfs_file_operations;
    -extern int relayfs_open(struct inode *inode, struct file *filp);
    -extern unsigned int relayfs_poll(struct file *filp, poll_table *wait);
    -extern int relayfs_mmap(struct file *filp, struct vm_area_struct *vma);
    -extern int relayfs_release(struct inode *inode, struct file *filp);
    -
    #endif /* _LINUX_RELAYFS_FS_H */


    --
    Jens Axboe

    -
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