switch hugetlbfs to ->read_iter()

... and fix the case when the area we are asked to read crosses
a hugepage boundary

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index c274aca8e8dc231cb4473b964bc3315058910968..5291c14ee6b8c7965b43edd2757114969979ecc0 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -34,6 +34,7 @@
 #include <linux/security.h>
 #include <linux/magic.h>
 #include <linux/migrate.h>
+#include <linux/uio.h>
 
 #include <asm/uaccess.h>
 
@@ -179,42 +180,33 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 }
 #endif
 
-static int
+static size_t
 hugetlbfs_read_actor(struct page *page, unsigned long offset,
-                       char __user *buf, unsigned long count,
-                       unsigned long size)
+                       struct iov_iter *to, unsigned long size)
 {
-       char *kaddr;
-       unsigned long left, copied = 0;
+       size_t copied = 0;
        int i, chunksize;
 
-       if (size > count)
-               size = count;
-
        /* Find which 4k chunk and offset with in that chunk */
        i = offset >> PAGE_CACHE_SHIFT;
        offset = offset & ~PAGE_CACHE_MASK;
 
        while (size) {
+               size_t n;
                chunksize = PAGE_CACHE_SIZE;
                if (offset)
                        chunksize -= offset;
                if (chunksize > size)
                        chunksize = size;
-               kaddr = kmap(&page[i]);
-               left = __copy_to_user(buf, kaddr + offset, chunksize);
-               kunmap(&page[i]);
-               if (left) {
-                       copied += (chunksize - left);
-                       break;
-               }
+               n = copy_page_to_iter(&page[i], offset, chunksize, to);
+               copied += n;
+               if (n != chunksize)
+                       return copied;
                offset = 0;
                size -= chunksize;
-               buf += chunksize;
-               copied += chunksize;
                i++;
        }
-       return copied ? copied : -EFAULT;
+       return copied;
 }
 
 /*
@@ -222,39 +214,34 @@ hugetlbfs_read_actor(struct page *page, unsigned long offset,
  * data. Its *very* similar to do_generic_mapping_read(), we can't use that
  * since it has PAGE_CACHE_SIZE assumptions.
  */
-static ssize_t hugetlbfs_read(struct file *filp, char __user *buf,
-                             size_t len, loff_t *ppos)
+static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
-       struct hstate *h = hstate_file(filp);
-       struct address_space *mapping = filp->f_mapping;
+       struct file *file = iocb->ki_filp;
+       struct hstate *h = hstate_file(file);
+       struct address_space *mapping = file->f_mapping;
        struct inode *inode = mapping->host;
-       unsigned long index = *ppos >> huge_page_shift(h);
-       unsigned long offset = *ppos & ~huge_page_mask(h);
+       unsigned long index = iocb->ki_pos >> huge_page_shift(h);
+       unsigned long offset = iocb->ki_pos & ~huge_page_mask(h);
        unsigned long end_index;
        loff_t isize;
        ssize_t retval = 0;
 
-       /* validate length */
-       if (len == 0)
-               goto out;
-
-       for (;;) {
+       while (iov_iter_count(to)) {
                struct page *page;
-               unsigned long nr, ret;
-               int ra;
+               size_t nr, copied;
 
                /* nr is the maximum number of bytes to copy from this page */
                nr = huge_page_size(h);
                isize = i_size_read(inode);
                if (!isize)
-                       goto out;
+                       break;
                end_index = (isize - 1) >> huge_page_shift(h);
-               if (index >= end_index) {
-                       if (index > end_index)
-                               goto out;
+               if (index > end_index)
+                       break;
+               if (index == end_index) {
                        nr = ((isize - 1) & ~huge_page_mask(h)) + 1;
                        if (nr <= offset)
-                               goto out;
+                               break;
                }
                nr = nr - offset;
 
@@ -265,39 +252,27 @@ static ssize_t hugetlbfs_read(struct file *filp, char __user *buf,
                         * We have a HOLE, zero out the user-buffer for the
                         * length of the hole or request.
                         */
-                       ret = len < nr ? len : nr;
-                       if (clear_user(buf, ret))
-                               ra = -EFAULT;
-                       else
-                               ra = 0;
+                       copied = iov_iter_zero(nr, to);
                } else {
                        unlock_page(page);
 
                        /*
                         * We have the page, copy it to user space buffer.
                         */
-                       ra = hugetlbfs_read_actor(page, offset, buf, len, nr);
-                       ret = ra;
+                       copied = hugetlbfs_read_actor(page, offset, to, nr);
                        page_cache_release(page);
                }
-               if (ra < 0) {
-                       if (retval == 0)
-                               retval = ra;
-                       goto out;
+               offset += copied;
+               retval += copied;
+               if (copied != nr && iov_iter_count(to)) {
+                       if (!retval)
+                               retval = -EFAULT;
+                       break;
                }
-
-               offset += ret;
-               retval += ret;
-               len -= ret;
                index += offset >> huge_page_shift(h);
                offset &= ~huge_page_mask(h);
-
-               /* short read or no more work */
-               if ((ret != nr) || (len == 0))
-                       break;
        }
-out:
-       *ppos = ((loff_t)index << huge_page_shift(h)) + offset;
+       iocb->ki_pos = ((loff_t)index << huge_page_shift(h)) + offset;
        return retval;
 }
 
@@ -721,7 +696,8 @@ static void init_once(void *foo)
 }
 
 const struct file_operations hugetlbfs_file_operations = {
-       .read                   = hugetlbfs_read,
+       .read                   = new_sync_read,
+       .read_iter              = hugetlbfs_read_iter,
        .mmap                   = hugetlbfs_file_mmap,
        .fsync                  = noop_fsync,
        .get_unmapped_area      = hugetlb_get_unmapped_area,