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 or not enough in a datablock. Otherwise pages will be marked as uptodate. The unhandled pages will be updated by readpage later. Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> --- Note that this patch was not formally sent to the list before. It's attached to email thread for discussion as it's still under development. - v1: The patch outline was suggested by Matthew. It went through a few reviews by Matthew offline. - v2: https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m442435c149d411c5c9d8019cff5915419b04bf10 This is a resend of v1. - v3: https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m55a709e6ba5ec59fe95323a67a7f3d6b1953e470 Fix page actor size to avoid a crash from squashfs_decompress(). Suggested by Phillip Lougher[1] [1] https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m687f82debb7667ff31982a05aef3eba081eb5039 - v4: https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#mf93267690ec2e841dade6a494fe72c84b61328d9 Fix to free page after used. Suggested by Xiongwei Song[2] Refactor the skip page logic to possible improve the performance. Suggested by Phillip Lougher[3] [2] https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m0e7b33d167b1ef0eb39b9f41c32ed3f80dfced18 [3] https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m1e0a8f8e4a98d79d14c81b66e197b6dc0a3b77a1 --- fs/squashfs/file.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c index a8e495d8eb86..91dfec792f4c 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 @@ -495,7 +496,83 @@ static int squashfs_read_folio(struct file *file, struct folio *folio) return 0; } +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; + size_t shift = msblk->block_log - PAGE_SHIFT; + loff_t req_end = readahead_pos(ractl) + readahead_length(ractl); + 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; + u64 block = 0; + int bsize, res, i, index; + int file_end = i_size_read(inode) >> msblk->block_log; + unsigned int max_pages = 1UL << shift; + + readahead_expand(ractl, start, (len | mask) + 1); + + if (readahead_pos(ractl) + readahead_length(ractl) < req_end || + file_end == 0) + return; + + pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL); + if (!pages) + return; + + actor = squashfs_page_actor_init_special(pages, max_pages, 0); + if (!actor) + goto out; + + for (;;) { + nr_pages = __readahead_batch(ractl, pages, max_pages); + if (!nr_pages) + break; + + if (readahead_pos(ractl) >= i_size_read(inode) || + nr_pages < max_pages) + goto skip_pages; + + index = pages[0]->index >> shift; + if ((pages[nr_pages - 1]->index >> shift) != index) + goto skip_pages; + + bsize = read_blocklist(inode, index, &block); + if (bsize == 0) + goto skip_pages; + + res = squashfs_read_data(inode->i_sb, block, bsize, NULL, + actor); + + if (res >= 0) + for (i = 0; i < nr_pages; i++) + SetPageUptodate(pages[i]); + + for (i = 0; i < nr_pages; i++) { + unlock_page(pages[i]); + put_page(pages[i]); + } + } + + kfree(actor); + kfree(pages); + return; + +skip_pages: + for (i = 0; i < nr_pages; i++) { + unlock_page(pages[i]); + put_page(pages[i]); + } + + kfree(actor); +out: + kfree(pages); +} const struct address_space_operations squashfs_aops = { .read_folio = squashfs_read_folio + .readahead = squashfs_readahead }; -- 2.36.0.550.gb090851708-goog
