iov_iter: hide iovec details behind ops function pointers

This moves the current iov_iter functions behind an ops struct of function
pointers.  The current iov_iter functions all work with memory which is
specified by iovec arrays of user space pointers.

This patch is part of a series that lets us specify memory with bio_vec arrays
of page pointers.  By moving to an iov_iter operation struct we can add that
support in later patches in this series by adding another set of function
pointers.

I only came to this after having initialy tried to teach the current iov_iter
functions about bio_vecs by introducing conditional branches that dealt with
bio_vecs in all the functions.  It wasn't pretty.  This approach seems to be
the lesser evil.

Signed-off-by: Zach Brown <zach.brown@oracle.com>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 429e861ea8f7189c56e89b356e092a292828e977..c3e198ec671de969e59f8b377fa2ec13c0d9ba0d 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -525,29 +525,68 @@ struct address_space;
 struct writeback_control;
 
 struct iov_iter {
-       const struct iovec *iov;
+       struct iov_iter_ops *ops;
+       unsigned long data;
        unsigned long nr_segs;
        size_t iov_offset;
        size_t count;
 };
 
-size_t iov_iter_copy_to_user_atomic(struct page *page,
-                struct iov_iter *i, unsigned long offset, size_t bytes);
-size_t iov_iter_copy_to_user(struct page *page,
-               struct iov_iter *i, unsigned long offset, size_t bytes);
-size_t iov_iter_copy_from_user_atomic(struct page *page,
-               struct iov_iter *i, unsigned long offset, size_t bytes);
-size_t iov_iter_copy_from_user(struct page *page,
-               struct iov_iter *i, unsigned long offset, size_t bytes);
-void iov_iter_advance(struct iov_iter *i, size_t bytes);
-int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
-size_t iov_iter_single_seg_count(struct iov_iter *i);
+struct iov_iter_ops {
+       size_t (*ii_copy_to_user_atomic)(struct page *, struct iov_iter *,
+                                        unsigned long, size_t);
+       size_t (*ii_copy_to_user)(struct page *, struct iov_iter *,
+                                 unsigned long, size_t);
+       size_t (*ii_copy_from_user_atomic)(struct page *, struct iov_iter *,
+                                          unsigned long, size_t);
+       size_t (*ii_copy_from_user)(struct page *, struct iov_iter *,
+                                         unsigned long, size_t);
+       void (*ii_advance)(struct iov_iter *, size_t);
+       int (*ii_fault_in_readable)(struct iov_iter *, size_t);
+       size_t (*ii_single_seg_count)(struct iov_iter *);
+};
+
+static inline size_t iov_iter_copy_to_user_atomic(struct page *page,
+                struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+       return i->ops->ii_copy_to_user_atomic(page, i, offset, bytes);
+}
+static inline size_t iov_iter_copy_to_user(struct page *page,
+               struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+       return i->ops->ii_copy_to_user(page, i, offset, bytes);
+}
+static inline size_t iov_iter_copy_from_user_atomic(struct page *page,
+                struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+       return i->ops->ii_copy_from_user_atomic(page, i, offset, bytes);
+}
+static inline size_t iov_iter_copy_from_user(struct page *page,
+               struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+       return i->ops->ii_copy_from_user(page, i, offset, bytes);
+}
+static inline void iov_iter_advance(struct iov_iter *i, size_t bytes)
+{
+       return i->ops->ii_advance(i, bytes);
+}
+static inline int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
+{
+       return i->ops->ii_fault_in_readable(i, bytes);
+}
+static inline size_t iov_iter_single_seg_count(struct iov_iter *i)
+{
+       return i->ops->ii_single_seg_count(i);
+}
+
+extern struct iov_iter_ops ii_iovec_ops;
 
 static inline void iov_iter_init(struct iov_iter *i,
                        const struct iovec *iov, unsigned long nr_segs,
                        size_t count, size_t written)
 {
-       i->iov = iov;
+       i->ops = &ii_iovec_ops;
+       i->data = (unsigned long)iov;
        i->nr_segs = nr_segs;
        i->iov_offset = 0;
        i->count = count + written;

diff --git a/mm/iov-iter.c b/mm/iov-iter.c
index 9f4143b56ecd9a81c8b2b60bf0b09b8270e0677e..d9f9238797b5459bbd729139ac00255d7f46905a 100644 (file)
--- a/mm/iov-iter.c
+++ b/mm/iov-iter.c
@@ -33,9 +33,10 @@ static size_t __iovec_copy_to_user_inatomic(char *vaddr,
  * were sucessfully copied.  If a fault is encountered then return the number of
  * bytes which were copied.
  */
-size_t iov_iter_copy_to_user_atomic(struct page *page,
+size_t ii_iovec_copy_to_user_atomic(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes)
 {
+       struct iovec *iov = (struct iovec *)i->data;
        char *kaddr;
        size_t copied;
 
@@ -43,45 +44,44 @@ size_t iov_iter_copy_to_user_atomic(struct page *page,
        kaddr = kmap_atomic(page, KM_USER0);
        if (likely(i->nr_segs == 1)) {
                int left;
-               char __user *buf = i->iov->iov_base + i->iov_offset;
+               char __user *buf = iov->iov_base + i->iov_offset;
                left = __copy_to_user_inatomic(buf, kaddr + offset, bytes);
                copied = bytes - left;
        } else {
                copied = __iovec_copy_to_user_inatomic(kaddr + offset,
-                                               i->iov, i->iov_offset, bytes);
+                                               iov, i->iov_offset, bytes);
        }
        kunmap_atomic(kaddr, KM_USER0);
 
        return copied;
 }
-EXPORT_SYMBOL(iov_iter_copy_to_user_atomic);
 
 /*
  * This has the same sideeffects and return value as
- * iov_iter_copy_to_user_atomic().
+ * ii_iovec_copy_to_user_atomic().
  * The difference is that it attempts to resolve faults.
  * Page must not be locked.
  */
-size_t iov_iter_copy_to_user(struct page *page,
+size_t ii_iovec_copy_to_user(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes)
 {
+       struct iovec *iov = (struct iovec *)i->data;
        char *kaddr;
        size_t copied;
 
        kaddr = kmap(page);
        if (likely(i->nr_segs == 1)) {
                int left;
-               char __user *buf = i->iov->iov_base + i->iov_offset;
+               char __user *buf = iov->iov_base + i->iov_offset;
                left = copy_to_user(buf, kaddr + offset, bytes);
                copied = bytes - left;
        } else {
                copied = __iovec_copy_to_user_inatomic(kaddr + offset,
-                                               i->iov, i->iov_offset, bytes);
+                                               iov, i->iov_offset, bytes);
        }
        kunmap(page);
        return copied;
 }
-EXPORT_SYMBOL(iov_iter_copy_to_user);
 
 
 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
@@ -111,9 +111,10 @@ static size_t __iovec_copy_from_user_inatomic(char *vaddr,
  * were successfully copied.  If a fault is encountered then return the number of
  * bytes which were copied.
  */
-size_t iov_iter_copy_from_user_atomic(struct page *page,
+size_t ii_iovec_copy_from_user_atomic(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes)
 {
+       struct iovec *iov = (struct iovec *)i->data;
        char *kaddr;
        size_t copied;
 
@@ -121,12 +122,12 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
        kaddr = kmap_atomic(page, KM_USER0);
        if (likely(i->nr_segs == 1)) {
                int left;
-               char __user *buf = i->iov->iov_base + i->iov_offset;
+               char __user *buf = iov->iov_base + i->iov_offset;
                left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
                copied = bytes - left;
        } else {
                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
-                                               i->iov, i->iov_offset, bytes);
+                                               iov, i->iov_offset, bytes);
        }
        kunmap_atomic(kaddr, KM_USER0);
 
@@ -136,32 +137,32 @@ EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 
 /*
  * This has the same sideeffects and return value as
- * iov_iter_copy_from_user_atomic().
+ * ii_iovec_copy_from_user_atomic().
  * The difference is that it attempts to resolve faults.
  * Page must not be locked.
  */
-size_t iov_iter_copy_from_user(struct page *page,
+size_t ii_iovec_copy_from_user(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes)
 {
+       struct iovec *iov = (struct iovec *)i->data;
        char *kaddr;
        size_t copied;
 
        kaddr = kmap(page);
        if (likely(i->nr_segs == 1)) {
                int left;
-               char __user *buf = i->iov->iov_base + i->iov_offset;
+               char __user *buf = iov->iov_base + i->iov_offset;
                left = __copy_from_user(kaddr + offset, buf, bytes);
                copied = bytes - left;
        } else {
                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
-                                               i->iov, i->iov_offset, bytes);
+                                               iov, i->iov_offset, bytes);
        }
        kunmap(page);
        return copied;
 }
-EXPORT_SYMBOL(iov_iter_copy_from_user);
 
-void iov_iter_advance(struct iov_iter *i, size_t bytes)
+void ii_iovec_advance(struct iov_iter *i, size_t bytes)
 {
        BUG_ON(i->count < bytes);
 
@@ -169,7 +170,7 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes)
                i->iov_offset += bytes;
                i->count -= bytes;
        } else {
-               const struct iovec *iov = i->iov;
+               struct iovec *iov = (struct iovec *)i->data;
                size_t base = i->iov_offset;
 
                /*
@@ -189,11 +190,10 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes)
                                base = 0;
                        }
                }
-               i->iov = iov;
+               i->data = (unsigned long)iov;
                i->iov_offset = base;
        }
 }
-EXPORT_SYMBOL(iov_iter_advance);
 
 /*
  * Fault in the first iovec of the given iov_iter, to a maximum length
@@ -204,23 +204,33 @@ EXPORT_SYMBOL(iov_iter_advance);
  * would be possible (callers must not rely on the fact that _only_ the
  * first iovec will be faulted with the current implementation).
  */
-int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
+int ii_iovec_fault_in_readable(struct iov_iter *i, size_t bytes)
 {
-       char __user *buf = i->iov->iov_base + i->iov_offset;
-       bytes = min(bytes, i->iov->iov_len - i->iov_offset);
+       struct iovec *iov = (struct iovec *)i->data;
+       char __user *buf = iov->iov_base + i->iov_offset;
+       bytes = min(bytes, iov->iov_len - i->iov_offset);
        return fault_in_pages_readable(buf, bytes);
 }
-EXPORT_SYMBOL(iov_iter_fault_in_readable);
 
 /*
  * Return the count of just the current iov_iter segment.
  */
-size_t iov_iter_single_seg_count(struct iov_iter *i)
+size_t ii_iovec_single_seg_count(struct iov_iter *i)
 {
-       const struct iovec *iov = i->iov;
+       struct iovec *iov = (struct iovec *)i->data;
        if (i->nr_segs == 1)
                return i->count;
        else
                return min(i->count, iov->iov_len - i->iov_offset);
 }
-EXPORT_SYMBOL(iov_iter_single_seg_count);
+
+struct iov_iter_ops ii_iovec_ops = {
+       .ii_copy_to_user_atomic = ii_iovec_copy_to_user_atomic,
+       .ii_copy_to_user = ii_iovec_copy_to_user,
+       .ii_copy_from_user_atomic = ii_iovec_copy_from_user_atomic,
+       .ii_copy_from_user = ii_iovec_copy_from_user,
+       .ii_advance = ii_iovec_advance,
+       .ii_fault_in_readable = ii_iovec_fault_in_readable,
+       .ii_single_seg_count = ii_iovec_single_seg_count,
+};
+EXPORT_SYMBOL(ii_iovec_ops);