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    Subject[PATCH 12/14] fs: implement kernel_read using __kernel_read
    Date
    Consolidate the two in-kernel read helpers to make upcoming changes
    easier. The only difference are the missing call to rw_verify_area
    in kernel_read, and an access_ok check that doesn't make sense for
    kernel buffers to start with.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    ---
    fs/read_write.c | 13 +++++--------
    1 file changed, 5 insertions(+), 8 deletions(-)

    diff --git a/fs/read_write.c b/fs/read_write.c
    index bd12af8a895c8..4e19152a7efe0 100644
    --- a/fs/read_write.c
    +++ b/fs/read_write.c
    @@ -453,15 +453,12 @@ ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)

    ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
    {
    - mm_segment_t old_fs;
    - ssize_t result;
    + ssize_t ret;

    - old_fs = get_fs();
    - set_fs(KERNEL_DS);
    - /* The cast to a user pointer is valid due to the set_fs() */
    - result = vfs_read(file, (void __user *)buf, count, pos);
    - set_fs(old_fs);
    - return result;
    + ret = rw_verify_area(READ, file, pos, count);
    + if (ret)
    + return ret;
    + return __kernel_read(file, buf, count, pos);
    }
    EXPORT_SYMBOL(kernel_read);

    --
    2.26.2
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