On Sun, Feb 17, 2013 at 10:05:01PM +0100, Alexander Aring wrote:
> Add pread and pwrite functions.
>
> Split read and write functions to save some space.
> The functions pread and pwrite saves and sets the file
> position to a given offset and restore them afterwards.
>
> Signed-off-by: Alexander Aring <alex.aring@xxxxxxxxx>
> ---
> fs/fs.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++----------
> include/fs.h | 2 ++
> 2 files changed, 77 insertions(+), 14 deletions(-)
>
> diff --git a/fs/fs.c b/fs/fs.c
> index 48d1c89..497a2ea 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -754,17 +754,12 @@ int ioctl(int fd, int request, void *buf)
> return ret;
> }
>
> -ssize_t read(int fd, void *buf, size_t count)
> +static ssize_t __read(FILE *f, void *buf, size_t count)
> {
> struct device_d *dev;
> struct fs_driver_d *fsdrv;
> - FILE *f;
> int ret;
>
> - if (check_fd(fd))
> - return -errno;
> -
> - f = &files[fd];
> dev = f->dev;
>
> fsdrv = dev_to_fs_driver(dev);
> @@ -777,18 +772,34 @@ ssize_t read(int fd, void *buf, size_t count)
>
> ret = fsdrv->read(dev, f, buf, count);
>
> - if (ret > 0)
> - f->pos += ret;
> if (ret < 0)
> errno = -ret;
> return ret;
> }
> -EXPORT_SYMBOL(read);
> +EXPORT_SYMBOL(pread);
>
> -ssize_t write(int fd, const void *buf, size_t count)
> +ssize_t pread(int fd, void *buf, size_t count, loff_t offset)
> +{
> + loff_t pos;
> + FILE *f;
> + int ret;
> +
> + if (check_fd(fd))
> + return -errno;
> +
> + f = &files[fd];
> +
> + pos = f->pos;
> + f->pos = offset;
> + ret = __read(f, buf, count);
> + f->pos = pos;
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(pread);
pread is exported twice with this patch. I fixed this while applying.
Sascha
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