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: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 1e57f36ea1b2f84ac43c486cf6aa9cff4b2280a0..b5f9d3daad0c30aae98f02b6caf794c7629d8bf3 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2733,8 +2733,8 @@ cifs_readdata_to_iov(struct cifs_readdata *rdata, const struct iovec *iov,
                /* go while there's data to be copied and no errors */
                if (copy && !rc) {
                        pdata = kmap(page);
-                       rc = memcpy_toiovecend(ii.iov, pdata, ii.iov_offset,
-                                               (int)copy);
+                       rc = memcpy_toiovecend(iov_iter_iovec(&ii), pdata,
+                                              ii.iov_offset, (int)copy);
                        kunmap(page);
                        if (!rc) {
                                *copied += copy;

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 633766ce6a1685f8c857ac7d4419b632e2216fb1..77865d1d769d9b33f1471ad58793c5978490c134 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1172,9 +1172,10 @@ static inline void fuse_page_descs_length_init(struct fuse_req *req,
                        req->page_descs[i].offset;
 }
 
-static inline unsigned long fuse_get_user_addr(const struct iov_iter *ii)
+static inline unsigned long fuse_get_user_addr(struct iov_iter *ii)
 {
-       return (unsigned long)ii->iov->iov_base + ii->iov_offset;
+       struct iovec *iov = iov_iter_iovec(ii);
+       return (unsigned long)iov->iov_base + ii->iov_offset;
 }
 
 static inline size_t fuse_get_frag_size(const struct iov_iter *ii,

diff --git a/fs/iov-iter.c b/fs/iov-iter.c
index 6cecab49b7caa3295a2b86e4d1064f99a9343d33..6cb6be0f18e811b08d3b25b57956f9e86f2b25a6 100644 (file)
--- a/fs/iov-iter.c
+++ b/fs/iov-iter.c
@@ -36,9 +36,10 @@ static size_t __iovec_copy_to_user(char *vaddr, const struct iovec *iov,
  * 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,
+static 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;
 
@@ -46,55 +47,52 @@ size_t iov_iter_copy_to_user_atomic(struct page *page,
        kaddr = kmap_atomic(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_inatomic(buf, kaddr + offset, bytes);
                copied = bytes - left;
        } else {
-               copied = __iovec_copy_to_user(kaddr + offset, i->iov,
+               copied = __iovec_copy_to_user(kaddr + offset, iov,
                                              i->iov_offset, bytes, 1);
        }
        kunmap_atomic(kaddr);
 
        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,
-               struct iov_iter *i, unsigned long offset, size_t bytes)
+static size_t ii_iovec_copy_to_user(struct page *page,
+               struct iov_iter *i, unsigned long offset, size_t bytes,
+               int check_access)
 {
+       struct iovec *iov = (struct iovec *)i->data;
        char *kaddr;
        size_t copied;
 
+       if (check_access) {
+               might_sleep();
+               if (generic_segment_checks(iov, &i->nr_segs, &bytes,
+                                          VERIFY_WRITE))
+                       return 0;
+       }
+
        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(kaddr + offset, i->iov,
+               copied = __iovec_copy_to_user(kaddr + offset, iov,
                                              i->iov_offset, bytes, 0);
        }
        kunmap(page);
        return copied;
 }
-EXPORT_SYMBOL(__iov_iter_copy_to_user);
-
-size_t iov_iter_copy_to_user(struct page *page,
-               struct iov_iter *i, unsigned long offset, size_t bytes)
-{
-       might_sleep();
-       if (generic_segment_checks(i->iov, &i->nr_segs, &bytes, VERIFY_WRITE))
-               return 0;
-       return __iov_iter_copy_to_user(page, i, offset, bytes);
-}
-EXPORT_SYMBOL(iov_iter_copy_to_user);
 
 static size_t __iovec_copy_from_user(char *vaddr, const struct iovec *iov,
                                     size_t base, size_t bytes, int atomic)
@@ -126,9 +124,10 @@ static size_t __iovec_copy_from_user(char *vaddr, const struct iovec *iov,
  * 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,
+static 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;
 
@@ -136,11 +135,11 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
        kaddr = kmap_atomic(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_inatomic(kaddr + offset, buf, bytes);
                copied = bytes - left;
        } else {
-               copied = __iovec_copy_from_user(kaddr + offset, i->iov,
+               copied = __iovec_copy_from_user(kaddr + offset, iov,
                                                i->iov_offset, bytes, 1);
        }
        kunmap_atomic(kaddr);
@@ -151,32 +150,32 @@ 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,
+static 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(kaddr + offset, i->iov,
+               copied = __iovec_copy_from_user(kaddr + offset, iov,
                                                i->iov_offset, bytes, 0);
        }
        kunmap(page);
        return copied;
 }
-EXPORT_SYMBOL(iov_iter_copy_from_user);
 
-void iov_iter_advance(struct iov_iter *i, size_t bytes)
+static void ii_iovec_advance(struct iov_iter *i, size_t bytes)
 {
        BUG_ON(i->count < bytes);
 
@@ -184,7 +183,7 @@ 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;
                unsigned long nr_segs = i->nr_segs;
 
@@ -206,12 +205,11 @@ 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;
                i->nr_segs = nr_segs;
        }
 }
-EXPORT_SYMBOL(iov_iter_advance);
 
 /*
  * Fault in the first iovec of the given iov_iter, to a maximum length
@@ -222,23 +220,33 @@ 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)
+static 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(const struct iov_iter *i)
+static size_t ii_iovec_single_seg_count(const struct iov_iter *i)
 {
-       const struct iovec *iov = i->iov;
+       const 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);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index bfc6eb05f03445504ee773656d64573d8f3fb19c..96120d51522c440a42c4823893dd334a9ee924de 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -290,31 +290,73 @@ 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_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(const 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, int);
+       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)(const 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, 0);
+}
+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, 1);
+}
+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(const 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;
@@ -322,6 +364,11 @@ static inline void iov_iter_init(struct iov_iter *i,
        iov_iter_advance(i, written);
 }
 
+static inline struct iovec *iov_iter_iovec(struct iov_iter *i)
+{
+       return (struct iovec *)i->data;
+}
+
 static inline size_t iov_iter_count(struct iov_iter *i)
 {
        return i->count;