mm: write iovec cleanup

[sfrench/cifs-2.6.git] / mm / filemap.h

diff --git a/mm/filemap.h b/mm/filemap.h
index a1e10a232e92a18e8a76c38ebc193c74bc94a1f6..b500d936cec59378eed59ef1cb7cff339d01e752 100644 (file)
--- a/mm/filemap.h
+++ b/mm/filemap.h
@@ -22,82 +22,82 @@ __filemap_copy_from_user_iovec_inatomic(char *vaddr,
 
 /*
  * Copy as much as we can into the page and return the number of bytes which
- * were sucessfully copied.  If a fault is encountered then clear the page
- * out to (offset+bytes) and return the number of bytes which were copied.
- *
- * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
- * to *NOT* zero any tail of the buffer that it failed to copy.  If it does,
- * and if the following non-atomic copy succeeds, then there is a small window
- * where the target page contains neither the data before the write, nor the
- * data after the write (it contains zero).  A read at this time will see
- * data that is inconsistent with any ordering of the read and the write.
- * (This has been detected in practice).
+ * were sucessfully copied.  If a fault is encountered then return the number of
+ * bytes which were copied.
  */
 static inline size_t
-filemap_copy_from_user(struct page *page, unsigned long offset,
-                       const char __user *buf, unsigned bytes)
+filemap_copy_from_user_atomic(struct page *page, unsigned long offset,
+                       const struct iovec *iov, unsigned long nr_segs,
+                       size_t base, size_t bytes)
 {
        char *kaddr;
-       int left;
+       size_t copied;
 
        kaddr = kmap_atomic(page, KM_USER0);
-       left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
+       if (likely(nr_segs == 1)) {
+               int left;
+               char __user *buf = iov->iov_base + base;
+               left = __copy_from_user_inatomic_nocache(kaddr + offset,
+                                                       buf, bytes);
+               copied = bytes - left;
+       } else {
+               copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset,
+                                                       iov, base, bytes);
+       }
        kunmap_atomic(kaddr, KM_USER0);
 
-       if (left != 0) {
-               /* Do it the slow way */
-               kaddr = kmap(page);
-               left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
-               kunmap(page);
-       }
-       return bytes - left;
+       return copied;
 }
 
 /*
- * This has the same sideeffects and return value as filemap_copy_from_user().
- * The difference is that on a fault we need to memset the remainder of the
- * page (out to offset+bytes), to emulate filemap_copy_from_user()'s
- * single-segment behaviour.
+ * This has the same sideeffects and return value as
+ * filemap_copy_from_user_atomic().
+ * The difference is that it attempts to resolve faults.
  */
 static inline size_t
-filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
-                       const struct iovec *iov, size_t base, size_t bytes)
+filemap_copy_from_user(struct page *page, unsigned long offset,
+                       const struct iovec *iov, unsigned long nr_segs,
+                        size_t base, size_t bytes)
 {
        char *kaddr;
        size_t copied;
 
-       kaddr = kmap_atomic(page, KM_USER0);
-       copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
-                                                        base, bytes);
-       kunmap_atomic(kaddr, KM_USER0);
-       if (copied != bytes) {
-               kaddr = kmap(page);
-               copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
-                                                                base, bytes);
-               if (bytes - copied)
-                       memset(kaddr + offset + copied, 0, bytes - copied);
-               kunmap(page);
+       kaddr = kmap(page);
+       if (likely(nr_segs == 1)) {
+               int left;
+               char __user *buf = iov->iov_base + base;
+               left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
+               copied = bytes - left;
+       } else {
+               copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset,
+                                                       iov, base, bytes);
        }
+       kunmap(page);
        return copied;
 }
 
 static inline void
-filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
+filemap_set_next_iovec(const struct iovec **iovp, unsigned long nr_segs,
+                                                size_t *basep, size_t bytes)
 {
-       const struct iovec *iov = *iovp;
-       size_t base = *basep;
+       if (likely(nr_segs == 1)) {
+               *basep += bytes;
+       } else {
+               const struct iovec *iov = *iovp;
+               size_t base = *basep;
 
-       while (bytes) {
-               int copy = min(bytes, iov->iov_len - base);
+               while (bytes) {
+                       int copy = min(bytes, iov->iov_len - base);
 
-               bytes -= copy;
-               base += copy;
-               if (iov->iov_len == base) {
-                       iov++;
-                       base = 0;
+                       bytes -= copy;
+                       base += copy;
+                       if (iov->iov_len == base) {
+                               iov++;
+                               base = 0;
+                       }
                }
+               *iovp = iov;
+               *basep = base;
        }
-       *iovp = iov;
-       *basep = base;
 }
 #endif