IB/core: Add umem function to read data from user-space
In some drivers there's a need to read data from a user space area that was pinned using ib_umem when running from a different process context. The ib_umem_copy_from function allows reading data from the physical pages pinned in the ib_umem struct. Signed-off-by: Haggai Eran <haggaie@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
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@ -292,3 +292,37 @@ int ib_umem_page_count(struct ib_umem *umem)
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return n;
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}
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EXPORT_SYMBOL(ib_umem_page_count);
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/*
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* Copy from the given ib_umem's pages to the given buffer.
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*
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* umem - the umem to copy from
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* offset - offset to start copying from
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* dst - destination buffer
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* length - buffer length
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*
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* Returns 0 on success, or an error code.
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*/
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int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offset,
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size_t length)
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{
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size_t end = offset + length;
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int ret;
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if (offset > umem->length || length > umem->length - offset) {
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pr_err("ib_umem_copy_from not in range. offset: %zd umem length: %zd end: %zd\n",
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offset, umem->length, end);
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return -EINVAL;
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}
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ret = sg_pcopy_to_buffer(umem->sg_head.sgl, umem->nmap, dst, length,
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offset + ib_umem_offset(umem));
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if (ret < 0)
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return ret;
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else if (ret != length)
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return -EINVAL;
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else
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return 0;
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}
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EXPORT_SYMBOL(ib_umem_copy_from);
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@ -84,6 +84,8 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
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size_t size, int access, int dmasync);
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void ib_umem_release(struct ib_umem *umem);
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int ib_umem_page_count(struct ib_umem *umem);
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int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offset,
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size_t length);
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#else /* CONFIG_INFINIBAND_USER_MEM */
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