Implement readahead callback for squashfs. It will read datablocks which cover pages in readahead request. For a few cases it will not mark page as uptodate, including: - file end is 0. - zero filled blocks. - current batch of pages isn't in the same datablock. - decompressor error. Otherwise pages will be marked as uptodate. The unhandled pages will be updated by readpage later. Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> Reported-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Reported-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxx> Reported-by: Xiongwei Song <Xiongwei.Song@xxxxxxxxxxxxx> Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- v5->v6: - use the new squashfs_page_actor_init_special() to handle short file cases as well. - use memzero_page(). v5: https://lore.kernel.org/lkml/20220606150305.1883410-4-hsinyi@xxxxxxxxxxxx/ v4: https://lore.kernel.org/lkml/20220601103922.1338320-4-hsinyi@xxxxxxxxxxxx/ v3: https://lore.kernel.org/lkml/20220523065909.883444-4-hsinyi@xxxxxxxxxxxx/ v2: https://lore.kernel.org/lkml/20220517082650.2005840-4-hsinyi@xxxxxxxxxxxx/ v1: https://lore.kernel.org/lkml/20220516105100.1412740-3-hsinyi@xxxxxxxxxxxx/ --- fs/squashfs/file.c | 92 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 91 insertions(+), 1 deletion(-) diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c index 7f0904b203294..f0c64ee272d5d 100644 --- a/fs/squashfs/file.c +++ b/fs/squashfs/file.c @@ -39,6 +39,7 @@ #include "squashfs_fs_sb.h" #include "squashfs_fs_i.h" #include "squashfs.h" +#include "page_actor.h" /* * Locate cache slot in range [offset, index] for specified inode. If @@ -496,7 +497,96 @@ static int squashfs_read_folio(struct file *file, struct folio *folio) return res; } +static void squashfs_readahead(struct readahead_control *ractl) +{ + struct inode *inode = ractl->mapping->host; + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; + size_t mask = (1UL << msblk->block_log) - 1; + unsigned short shift = msblk->block_log - PAGE_SHIFT; + loff_t start = readahead_pos(ractl) & ~mask; + size_t len = readahead_length(ractl) + readahead_pos(ractl) - start; + struct squashfs_page_actor *actor; + unsigned int nr_pages = 0; + struct page **pages; + int i, file_end = i_size_read(inode) >> msblk->block_log; + unsigned int max_pages = 1UL << shift; + + readahead_expand(ractl, start, (len | mask) + 1); + + if (file_end == 0) + return; + + pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL); + if (!pages) + return; + + for (;;) { + pgoff_t index; + int res, bsize; + u64 block = 0; + unsigned int expected; + + nr_pages = __readahead_batch(ractl, pages, max_pages); + if (!nr_pages) + break; + + if (readahead_pos(ractl) >= i_size_read(inode)) + goto skip_pages; + + index = pages[0]->index >> shift; + if ((pages[nr_pages - 1]->index >> shift) != index) + goto skip_pages; + + expected = index == file_end ? + (i_size_read(inode) & (msblk->block_size - 1)) : + msblk->block_size; + + bsize = read_blocklist(inode, index, &block); + if (bsize == 0) + goto skip_pages; + + actor = squashfs_page_actor_init_special(msblk, pages, nr_pages, + expected); + if (!actor) + goto skip_pages; + + res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor); + + kfree(actor); + + if (res == expected) { + int bytes; + + /* Last page (if present) may have trailing bytes not filled */ + bytes = res % PAGE_SIZE; + if (pages[nr_pages - 1]->index == file_end && bytes) + memzero_page(pages[nr_pages - 1], bytes, + PAGE_SIZE - bytes); + + for (i = 0; i < nr_pages; i++) { + flush_dcache_page(pages[i]); + SetPageUptodate(pages[i]); + } + } + + for (i = 0; i < nr_pages; i++) { + unlock_page(pages[i]); + put_page(pages[i]); + } + } + + kfree(pages); + return; + +skip_pages: + for (i = 0; i < nr_pages; i++) { + unlock_page(pages[i]); + put_page(pages[i]); + } + kfree(pages); +} const struct address_space_operations squashfs_aops = { - .read_folio = squashfs_read_folio + .read_folio = squashfs_read_folio, + .readahead = squashfs_readahead }; -- 2.36.1.476.g0c4daa206d-goog
