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From: Hsin-Yi Wang <hsinyi@chromium.org>
To: Phillip Lougher <phillip@squashfs.org.uk>,
	Matthew Wilcox <willy@infradead.org>,
	Xiongwei Song <Xiongwei.Song@windriver.com>
Cc: Zheng Liang <zhengliang6@huawei.com>,
	Zhang Yi <yi.zhang@huawei.com>, Hou Tao <houtao1@huawei.com>,
	Miao Xie <miaoxie@huawei.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-mm @ kvack . org" <linux-mm@kvack.org>,
	"squashfs-devel @ lists . sourceforge . net" 
	<squashfs-devel@lists.sourceforge.net>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 3/3] squashfs: implement readahead
Date: Tue, 17 May 2022 16:26:54 +0800	[thread overview]
Message-ID: <20220517082650.2005840-4-hsinyi@chromium.org> (raw)
In-Reply-To: <20220517082650.2005840-1-hsinyi@chromium.org>

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.

Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reported-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: Xiongwei Song <sxwjean@gmail.com>
---
v1->v2: remove unused check on readahead_expand().
v1: https://lore.kernel.org/lkml/20220516105100.1412740-3-hsinyi@chromium.org/
---
 fs/squashfs/file.c | 77 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 76 insertions(+), 1 deletion(-)

diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index a8e495d8eb86..e10a55c5b1eb 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 +496,81 @@ 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 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 (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
+	.read_folio = squashfs_read_folio,
+	.readahead = squashfs_readahead
 };
-- 
2.36.0.550.gb090851708-goog


  parent reply	other threads:[~2022-05-17  8:29 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-17  8:26 [PATCH v2 0/3] Implement readahead for squashfs Hsin-Yi Wang
2022-05-17  8:26 ` [PATCH v2 1/3] Revert "squashfs: provide backing_dev_info in order to disable read-ahead" Hsin-Yi Wang
2022-05-17  9:15   ` Xiongwei Song
2022-05-17  8:26 ` [PATCH v2 2/3] squashfs: always build "file direct" version of page actor Hsin-Yi Wang
2022-05-17  8:26 ` Hsin-Yi Wang [this message]
2022-05-17  9:16   ` [PATCH v2 3/3] squashfs: implement readahead Xiongwei Song
2022-05-19  7:56     ` Hsin-Yi Wang
2022-05-19  8:09   ` Hsin-Yi Wang
2022-05-20  3:02     ` Phillip Lougher
2022-05-20  7:38       ` Hsin-Yi Wang
2022-05-20 20:21         ` Phillip Lougher
2022-05-23  7:00           ` Hsin-Yi Wang

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