diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/truncate.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/mm/truncate.c b/mm/truncate.c index 18aded3a89f..61a183b89df 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -626,3 +626,43 @@ int vmtruncate_range(struct inode *inode, loff_t lstart, loff_t lend) return 0; } + +/** + * 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 unmap_start = round_up(lstart, PAGE_SIZE); + loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1; + /* + * 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. + */ + + /* + * 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); |