}
EXPORT_SYMBOL(vmtruncate);
-int vmtruncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+/**
+ * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
+ * @inode: inode
+ * @lstart: offset of beginning of hole
+ * @lend: offset of last byte of hole
+ *
+ * This function should typically be called before the filesystem
+ * releases resources associated with the freed range (eg. deallocates
+ * blocks). This way, pagecache will always stay logically coherent
+ * with on-disk format, and the filesystem would not have to deal with
+ * situations such as writepage being called for a page that has already
+ * had its underlying blocks deallocated.
+ */
+void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
{
struct address_space *mapping = inode->i_mapping;
- loff_t holebegin = round_up(lstart, PAGE_SIZE);
- loff_t holelen = 1 + lend - holebegin;
-
+ loff_t unmap_start = round_up(lstart, PAGE_SIZE);
+ loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
/*
- * If the underlying filesystem is not going to provide
- * a way to truncate a range of blocks (punch a hole) -
- * we should return failure right now.
+ * This rounding is currently just for example: unmap_mapping_range
+ * expands its hole outwards, whereas we want it to contract the hole
+ * inwards. However, existing callers of truncate_pagecache_range are
+ * doing their own page rounding first; and truncate_inode_pages_range
+ * currently BUGs if lend is not pagealigned-1 (it handles partial
+ * page at start of hole, but not partial page at end of hole). Note
+ * unmap_mapping_range allows holelen 0 for all, and we allow lend -1.
*/
- if (!inode->i_op->truncate_range)
- return -ENOSYS;
-
- mutex_lock(&inode->i_mutex);
- inode_dio_wait(inode);
- unmap_mapping_range(mapping, holebegin, holelen, 1);
- inode->i_op->truncate_range(inode, lstart, lend);
- /* unmap again to remove racily COWed private pages */
- unmap_mapping_range(mapping, holebegin, holelen, 1);
- mutex_unlock(&inode->i_mutex);
- return 0;
+ /*
+ * Unlike in truncate_pagecache, unmap_mapping_range is called only
+ * once (before truncating pagecache), and without "even_cows" flag:
+ * hole-punching should not remove private COWed pages from the hole.
+ */
+ if ((u64)unmap_end > (u64)unmap_start)
+ unmap_mapping_range(mapping, unmap_start,
+ 1 + unmap_end - unmap_start, 0);
+ truncate_inode_pages_range(mapping, lstart, lend);
}
+EXPORT_SYMBOL(truncate_pagecache_range);