On Mon, Mar 22, 2010 at 08:12:45PM -0400, Oren Laadan wrote:
> On Mon, 22 Mar 2010, Nick Piggin wrote:
>
> > On Thu, Mar 18, 2010 at 08:59:45PM -0400, Oren Laadan wrote:
> > > These two are used in the next patch when calling vfs_read/write()
> >
> > Said next patch didn't seem to make it to fsdevel.
>
> Thanks for reviewing, and sorry about this glitch - see below.
>
> >
> > Should it at least go to fs/internal.h?
>
> Sure.
>
> So Here is the relevant hunk from said patch (the entire
> patch is: https://patchwork.kernel.org/patch/86389/):
>
> +/*
> + * Helpers to write(read) from(to) kernel space to(from) the checkpoint
> + * image file descriptor (similar to how a core-dump is performed).
> + *
> + * ckpt_kwrite() - write a kernel-space buffer to the checkpoint image
> + * ckpt_kread() - read from the checkpoint image to a kernel-space buffer
Hmm, OK. Slightly-more-write(2) type of write.
fs/splice.c code also has a kernel_write and readv. Not sure if there is
any other common code. But maybe it would be better to put together some
useful helpers under fs/ rather than a ckpt specific thing.
> + */
> +
> +static inline int _ckpt_kwrite(struct file *file, void *addr, int count)
> +{
> + void __user *uaddr = (__force void __user *) addr;
> + ssize_t nwrite;
> + int nleft;
> +
> + for (nleft = count; nleft; nleft -= nwrite) {
> + loff_t pos = file_pos_read(file);
> + nwrite = vfs_write(file, uaddr, nleft, &pos);
> + file_pos_write(file, pos);
> + if (nwrite < 0) {
> + if (nwrite == -EAGAIN)
> + nwrite = 0;
> + else
> + return nwrite;
> + }
> + uaddr += nwrite;
> + }
> + return 0;
> +}
> +
> +int ckpt_kwrite(struct ckpt_ctx *ctx, void *addr, int count)
> +{
> + mm_segment_t fs;
> + int ret;
> +
> + fs = get_fs();
> + set_fs(KERNEL_DS);
> + ret = _ckpt_kwrite(ctx->file, addr, count);
> + set_fs(fs);
> +
> + ctx->total += count;
> + return ret;
> +}
> +
> +static inline int _ckpt_kread(struct file *file, void *addr, int count)
> +{
> + void __user *uaddr = (__force void __user *) addr;
> + ssize_t nread;
> + int nleft;
> +
> + for (nleft = count; nleft; nleft -= nread) {
> + loff_t pos = file_pos_read(file);
> + nread = vfs_read(file, uaddr, nleft, &pos);
> + file_pos_write(file, pos);
> + if (nread <= 0) {
> + if (nread == -EAGAIN) {
> + nread = 0;
> + continue;
> + } else if (nread == 0)
> + nread = -EPIPE; /* unexecpted EOF */
> + return nread;
> + }
> + uaddr += nread;
> + }
> + return 0;
> +}
> +
> +int ckpt_kread(struct ckpt_ctx *ctx, void *addr, int count)
> +{
> + mm_segment_t fs;
> + int ret;
> +
> + fs = get_fs();
> + set_fs(KERNEL_DS);
> + ret = _ckpt_kread(ctx->file , addr, count);
> + set_fs(fs);
> +
> + ctx->total += count;
> + return ret;
> +}
>
> Oren.
> --
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