On 31/05/2022 21:47, Andrew Morton wrote:
On Mon, 23 May 2022 14:59:13 +0800 Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote:
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.
- decompressor error.
Otherwise pages will be marked as uptodate. The unhandled pages will be
updated by readpage later.
...
The choice of types seems somewhat confused.
@@ -495,7 +496,95 @@ 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;
block_log is unsigned short. Why size_t?
+ 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;
OK.
+ struct page **pages;
+ u64 block = 0;
+ int bsize, res, i, index, bytes, expected;
`res' could be local to the inner loop.
`i' is used in situations where an unsigned type would be more
appropriate. If it is made unsigned then `i' is no longer a suitable
identifier. Doesn't matter much.
`index' is from page.index, which is pgoff_t.
`bytes' could be local to the innermost loop.
`expected' is inappropriately a signed type and could be local to the
inner loop.
+ int file_end = i_size_read(inode) >> msblk->block_log;
+ unsigned int max_pages = 1UL << shift;
+ void *pageaddr;
+
pageaddr could be made local to the innermost scope.
Apart from that the patch and updated error handling looks
good.
Phillip
+ readahead_expand(ractl, start, (len | mask) + 1);
+
+ if (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;
+
+ 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;
+
+ res = squashfs_read_data(inode->i_sb, block, bsize, NULL,
+ actor);
+
+ if (res == expected) {
+ /* Last page may have trailing bytes not filled */
+ bytes = res % PAGE_SIZE;
+ if (bytes) {
+ pageaddr = kmap_atomic(pages[nr_pages - 1]);
+ memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
+ kunmap_atomic(pageaddr);
+ }
+
+ for (i = 0; i < nr_pages; i++)
+ SetPageUptodate(pages[i]);
+ }
res == -EIO is unhandled?
+ 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
+ .read_folio = squashfs_read_folio,
+ .readahead = squashfs_readahead
};
