diff options
| -rw-r--r-- | fs/hugetlbfs/inode.c | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8f8e13385e9..04598e12c48 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -179,6 +179,130 @@ full_search: } #endif +static int +hugetlbfs_read_actor(struct page *page, unsigned long offset, + char __user *buf, unsigned long count, + unsigned long size) +{ + char *kaddr; + unsigned long left, 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) { + 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; + } + offset = 0; + size -= chunksize; + buf += chunksize; + copied += chunksize; + i++; + } + return copied ? copied : -EFAULT; +} + +/* + * Support for read() - Find the page attached to f_mapping and copy out the + * 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) +{ + struct address_space *mapping = filp->f_mapping; + struct inode *inode = mapping->host; + unsigned long index = *ppos >> HPAGE_SHIFT; + unsigned long offset = *ppos & ~HPAGE_MASK; + unsigned long end_index; + loff_t isize; + ssize_t retval = 0; + + mutex_lock(&inode->i_mutex); + + /* validate length */ + if (len == 0) + goto out; + + isize = i_size_read(inode); + if (!isize) + goto out; + + end_index = (isize - 1) >> HPAGE_SHIFT; + for (;;) { + struct page *page; + int nr, ret; + + /* nr is the maximum number of bytes to copy from this page */ + nr = HPAGE_SIZE; + if (index >= end_index) { + if (index > end_index) + goto out; + nr = ((isize - 1) & ~HPAGE_MASK) + 1; + if (nr <= offset) { + goto out; + } + } + nr = nr - offset; + + /* Find the page */ + page = find_get_page(mapping, index); + if (unlikely(page == NULL)) { + /* + * 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)) + ret = -EFAULT; + } else { + /* + * We have the page, copy it to user space buffer. + */ + ret = hugetlbfs_read_actor(page, offset, buf, len, nr); + } + if (ret < 0) { + if (retval == 0) + retval = ret; + if (page) + page_cache_release(page); + goto out; + } + + offset += ret; + retval += ret; + len -= ret; + index += offset >> HPAGE_SHIFT; + offset &= ~HPAGE_MASK; + + if (page) + page_cache_release(page); + + /* short read or no more work */ + if ((ret != nr) || (len == 0)) + break; + } +out: + *ppos = ((loff_t)index << HPAGE_SHIFT) + offset; + mutex_unlock(&inode->i_mutex); + return retval; +} + /* * Read a page. Again trivial. If it didn't already exist * in the page cache, it is zero-filled. @@ -581,6 +705,7 @@ static void init_once(void *foo, struct kmem_cache *cachep, unsigned long flags) } const struct file_operations hugetlbfs_file_operations = { + .read = hugetlbfs_read, .mmap = hugetlbfs_file_mmap, .fsync = simple_sync_file, .get_unmapped_area = hugetlb_get_unmapped_area, |