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authorVegard Nossum <vegard.nossum@oracle.com>2016-10-08 11:18:07 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2016-10-14 20:00:34 -0400
commitffecee4f2442bb8cb6b34c3335fef4eb50c22fdd (patch)
tree53d6e7bcb5ff21f6f72d12d905b5173b35c2987a /lib
parentde34f4da7f62ff59ac6e1ef320b0fcfa3296fce3 (diff)
iov_iter: kernel-doc import_iovec() and rw_copy_check_uvector()
Both import_iovec() and rw_copy_check_uvector() take an array (typically small and on-stack) which is used to hold an iovec array copy from userspace. This is to avoid an expensive memory allocation in the fast path (i.e. few iovec elements). The caller may have to check whether these functions actually used the provided buffer or allocated a new one -- but this differs between the too. Let's just add a kernel doc to clarify what the semantics are for each function. Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'lib')
-rw-r--r--lib/iov_iter.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7312e7784611..f0c7f1481bae 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1139,6 +1139,28 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
}
EXPORT_SYMBOL(dup_iter);
+/**
+ * import_iovec() - Copy an array of &struct iovec from userspace
+ * into the kernel, check that it is valid, and initialize a new
+ * &struct iov_iter iterator to access it.
+ *
+ * @type: One of %READ or %WRITE.
+ * @uvector: Pointer to the userspace array.
+ * @nr_segs: Number of elements in userspace array.
+ * @fast_segs: Number of elements in @iov.
+ * @iov: (input and output parameter) Pointer to pointer to (usually small
+ * on-stack) kernel array.
+ * @i: Pointer to iterator that will be initialized on success.
+ *
+ * If the array pointed to by *@iov is large enough to hold all @nr_segs,
+ * then this function places %NULL in *@iov on return. Otherwise, a new
+ * array will be allocated and the result placed in *@iov. This means that
+ * the caller may call kfree() on *@iov regardless of whether the small
+ * on-stack array was used or not (and regardless of whether this function
+ * returns an error or not).
+ *
+ * Return: 0 on success or negative error code on error.
+ */
int import_iovec(int type, const struct iovec __user * uvector,
unsigned nr_segs, unsigned fast_segs,
struct iovec **iov, struct iov_iter *i)