debug lk

hc

2024-02-20 e636c8d336489bf3eed5878299e6cc045bbad077

 kernel/drivers/block/brd.c
..
..
@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * Ram backed block device driver.
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  *
..
..
@@ -79,11 +80,9 @@
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 }
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81
 
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 /*
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- * Look up and return a brd's page for a given sector.
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- * If one does not exist, allocate an empty page, and insert that. Then
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- * return it.
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+ * Insert a new page for a given sector, if one does not already exist.
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  */
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-static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
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+static int brd_insert_page(struct brd_device *brd, sector_t sector)
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 {
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 	pgoff_t idx;
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 	struct page *page;
..
..
@@ -91,7 +90,7 @@
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 	page = brd_lookup_page(brd, sector);
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 	if (page)
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-		return page;
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+		return 0;
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94
 
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 	/*
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 	 * Must use NOIO because we don't want to recurse back into the
..
..
@@ -100,11 +99,11 @@
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 	gfp_flags = GFP_NOIO | __GFP_ZERO | __GFP_HIGHMEM;
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 	page = alloc_page(gfp_flags);
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 	if (!page)
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-		return NULL;
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+		return -ENOMEM;
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 	if (radix_tree_preload(GFP_NOIO)) {
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 		__free_page(page);
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-		return NULL;
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+		return -ENOMEM;
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 	}
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 	spin_lock(&brd->brd_lock);
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..
@@ -119,8 +118,7 @@
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 	spin_unlock(&brd->brd_lock);
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 	radix_tree_preload_end();
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-
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-	return page;
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+	return 0;
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 }
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123
 
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 /*
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..
@@ -153,6 +151,12 @@
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 		pos++;
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152
 
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 		/*
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+		 * It takes 3.4 seconds to remove 80GiB ramdisk.
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+		 * So, we need cond_resched to avoid stalling the CPU.
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+		 */
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+		cond_resched();
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+
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+		/*
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 		 * This assumes radix_tree_gang_lookup always returns as
157
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 		 * many pages as possible. If the radix-tree code changes,
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 		 * so will this have to.
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@@ -167,16 +171,17 @@
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 {
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 	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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 	size_t copy;
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+	int ret;
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 	copy = min_t(size_t, n, PAGE_SIZE - offset);
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-	if (!brd_insert_page(brd, sector))
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-		return -ENOSPC;
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+	ret = brd_insert_page(brd, sector);
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+	if (ret)
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+		return ret;
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 	if (copy < n) {
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 		sector += copy >> SECTOR_SHIFT;
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-		if (!brd_insert_page(brd, sector))
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-			return -ENOSPC;
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+		ret = brd_insert_page(brd, sector);
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 	}
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-	return 0;
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+	return ret;
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 }
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 /*
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@@ -275,7 +280,7 @@
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 	return err;
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 }
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282
 
278
-static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
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+static blk_qc_t brd_submit_bio(struct bio *bio)
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 {
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 	struct brd_device *brd = bio->bi_disk->private_data;
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 	struct bio_vec bvec;
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@@ -289,6 +294,10 @@
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 	bio_for_each_segment(bvec, bio, iter) {
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 		unsigned int len = bvec.bv_len;
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 		int err;
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+
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+		/* Don't support un-aligned buffer */
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+		WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) ||
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+				(len & (SECTOR_SIZE - 1)));
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 		err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset,
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 				  bio_op(bio), sector);
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@@ -319,6 +328,7 @@
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328
 
320
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 static const struct block_device_operations brd_fops = {
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 	.owner =		THIS_MODULE,
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+	.submit_bio =		brd_submit_bio,
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 	.rw_page =		brd_rw_page,
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 };
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..
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@@ -370,12 +380,9 @@
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 	spin_lock_init(&brd->brd_lock);
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 	INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
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382
 
373
-	brd->brd_queue = blk_alloc_queue(GFP_KERNEL);
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+	brd->brd_queue = blk_alloc_queue(NUMA_NO_NODE);
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384
 	if (!brd->brd_queue)
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 		goto out_free_dev;
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-
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-	blk_queue_make_request(brd->brd_queue, brd_make_request);
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-	blk_queue_max_hw_sectors(brd->brd_queue, 1024);
379
386
 
380
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 	/* This is so fdisk will align partitions on 4k, because of
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 	 * direct_access API needing 4k alignment, returning a PFN
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..
@@ -394,7 +401,6 @@
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 	disk->flags		= GENHD_FL_EXT_DEVT;
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 	sprintf(disk->disk_name, "ram%d", i);
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 	set_capacity(disk, rd_size * 2);
397
-	brd->brd_queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO;
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404
 
399
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 	/* Tell the block layer that this is not a rotational device */
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 	blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue);