diff options
| -rw-r--r-- | include/linux/pagemap.h | 2 | ||||
| -rw-r--r-- | mm/readahead.c | 75 |
2 files changed, 77 insertions, 0 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 4220ded38f4b..63ca6430aef5 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -839,6 +839,8 @@ void page_cache_ra_unbounded(struct readahead_control *, void page_cache_sync_ra(struct readahead_control *, unsigned long req_count); void page_cache_async_ra(struct readahead_control *, struct page *, unsigned long req_count); +void readahead_expand(struct readahead_control *ractl, + loff_t new_start, size_t new_len); /** * page_cache_sync_readahead - generic file readahead diff --git a/mm/readahead.c b/mm/readahead.c index 5b423ecc99f1..d589f147f4c2 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -638,3 +638,78 @@ SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count) { return ksys_readahead(fd, offset, count); } + +/** + * readahead_expand - Expand a readahead request + * @ractl: The request to be expanded + * @new_start: The revised start + * @new_len: The revised size of the request + * + * Attempt to expand a readahead request outwards from the current size to the + * specified size by inserting locked pages before and after the current window + * to increase the size to the new window. This may involve the insertion of + * THPs, in which case the window may get expanded even beyond what was + * requested. + * + * The algorithm will stop if it encounters a conflicting page already in the + * pagecache and leave a smaller expansion than requested. + * + * The caller must check for this by examining the revised @ractl object for a + * different expansion than was requested. + */ +void readahead_expand(struct readahead_control *ractl, + loff_t new_start, size_t new_len) +{ + struct address_space *mapping = ractl->mapping; + struct file_ra_state *ra = ractl->ra; + pgoff_t new_index, new_nr_pages; + gfp_t gfp_mask = readahead_gfp_mask(mapping); + + new_index = new_start / PAGE_SIZE; + + /* Expand the leading edge downwards */ + while (ractl->_index > new_index) { + unsigned long index = ractl->_index - 1; + struct page *page = xa_load(&mapping->i_pages, index); + + if (page && !xa_is_value(page)) + return; /* Page apparently present */ + + page = __page_cache_alloc(gfp_mask); + if (!page) + return; + if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) { + put_page(page); + return; + } + + ractl->_nr_pages++; + ractl->_index = page->index; + } + + new_len += new_start - readahead_pos(ractl); + new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE); + + /* Expand the trailing edge upwards */ + while (ractl->_nr_pages < new_nr_pages) { + unsigned long index = ractl->_index + ractl->_nr_pages; + struct page *page = xa_load(&mapping->i_pages, index); + + if (page && !xa_is_value(page)) + return; /* Page apparently present */ + + page = __page_cache_alloc(gfp_mask); + if (!page) + return; + if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) { + put_page(page); + return; + } + ractl->_nr_pages++; + if (ra) { + ra->size++; + ra->async_size++; + } + } +} +EXPORT_SYMBOL(readahead_expand); |