btrfs: fix wrong bvec_len in btrfs_csum_one_bio()

Fixed below WARNING.

WARNING: CPU: 0 PID: 511 at /home/mlin/linux/fs/btrfs/ordered-data.c:288
btrfs_add_ordered_sum+0x5e/0x8e()
Modules linked in:
CPU: 0 PID: 511 Comm: kworker/u2:4 Not tainted 3.18.0-00029-g30fd029 torvalds#68
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
01/01/2011
Workqueue: btrfs-worker btrfs_worker_helper
0000000000000009 ffff88001e357c58 ffffffff81488839 0000000000000002
0000000000000000 ffff88001e357c98 ffffffff8103b8a3 ffff88001e357c88
ffffffff8124ec83 ffff88001ddd4000 ffff88001d8e8000 ffff88001df248a0
Call Trace:
[<ffffffff81488839>] dump_stack+0x4f/0x7c
[<ffffffff8103b8a3>] warn_slowpath_common+0x81/0x9b
[<ffffffff8124ec83>] ? btrfs_add_ordered_sum+0x5e/0x8e
[<ffffffff8103b8d7>] warn_slowpath_null+0x1a/0x1c
[<ffffffff8124ec83>] btrfs_add_ordered_sum+0x5e/0x8e
[<ffffffff8122e895>] btrfs_csum_one_bio+0x16a/0x3de
[<ffffffff81232929>] ? btrfs_async_submit_limit+0x28/0x28
[<ffffffff8123bebb>] __btrfs_submit_bio_start+0x1d/0x27
[<ffffffff81230d37>] run_one_async_start+0x27/0x32
[<ffffffff81261932>] normal_work_helper+0xf9/0x2fd
[<ffffffff81261b48>] btrfs_worker_helper+0x12/0x14
[<ffffffff8104ded7>] process_one_work+0x1ca/0x376
[<ffffffff8104e319>] worker_thread+0x267/0x366
[<ffffffff8104e0b2>] ? process_scheduled_works+0x2f/0x2f
[<ffffffff81051e7c>] kthread+0xd2/0xda
[<ffffffff81480000>] ? br_multicast_set_hash_max+0x4d/0xcd
[<ffffffff81051daa>] ? kthread_freezable_should_stop+0x48/0x48
[<ffffffff8148da6c>] ret_from_fork+0x7c/0xb0
[<ffffffff81051daa>] ? kthread_freezable_should_stop+0x48/0x48

Signed-off-by: Ming Lin <minggr.net>

fs/btrfs/extent_io.c

@@ -2462,27 +2462,27 @@ static void end_bio_extent_writepage(struct bio *bio, int err)
 
 	bio_for_each_page_all(bvec, bio, iter) {
 		struct page *page = bvec.bv_page;
+		unsigned int bv_len = min_t(unsigned int, bvec.bv_len, PAGE_CACHE_SIZE);
 
 		/* We always issue full-page reads, but if some block
 		 * in a page fails to read, blk_update_request() will
 		 * advance bv_offset and adjust bv_len to compensate.
 		 * Print a warning for nonzero offsets, and an error
 		 * if they don't add up to a full page.  */
 		if (bvec.bv_offset) {
-			if (bvec.bv_offset + bvec.bv_len != PAGE_CACHE_SIZE)
+			if (bvec.bv_offset + bv_len != PAGE_CACHE_SIZE)
 				btrfs_err(BTRFS_I(page->mapping->host)->root->fs_info,
 				   "partial page write in btrfs with offset %u and length %u",
-					bvec.bv_offset, bvec.bv_len);
+					bvec.bv_offset, bv_len);
 			else
 				btrfs_info(BTRFS_I(page->mapping->host)->root->fs_info,
 				   "incomplete page write in btrfs with offset %u and "
 				   "length %u",
-					bvec.bv_offset, bvec.bv_len);
+					bvec.bv_offset, bv_len);
 		}
 
 		start = page_offset(page);
-		end = start + bvec.bv_offset
-			+ min_t(unsigned int, bvec.bv_len, PAGE_CACHE_SIZE) - 1;
+		end = start + bvec.bv_offset + bv_len - 1;
 
 		if (end_extent_writepage(page, err, start, end))
 			continue;
@@ -2538,6 +2538,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
 	bio_for_each_page_all(bvec, bio, iter) {
 		struct page *page = bvec.bv_page;
 		struct inode *inode = page->mapping->host;
+		unsigned int bv_len = min_t(unsigned int, bvec.bv_len, PAGE_CACHE_SIZE);
 
 		pr_debug("end_bio_extent_readpage: bi_sector=%llu, err=%d, "
 			 "mirror=%u\n", (u64)bio->bi_iter.bi_sector, err,
@@ -2550,21 +2551,20 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
 		 * Print a warning for nonzero offsets, and an error
 		 * if they don't add up to a full page.  */
 		if (bvec.bv_offset) {
-			if (bvec.bv_offset + bvec.bv_len != PAGE_CACHE_SIZE)
+			if (bvec.bv_offset + bv_len != PAGE_CACHE_SIZE)
 				btrfs_err(BTRFS_I(page->mapping->host)->root->fs_info,
 				   "partial page read in btrfs with offset %u and length %u",
-					bvec.bv_offset, bvec.bv_len);
+					bvec.bv_offset, bv_len);
 			else
 				btrfs_info(BTRFS_I(page->mapping->host)->root->fs_info,
 				   "incomplete page read in btrfs with offset %u and "
 				   "length %u",
-					bvec.bv_offset, bvec.bv_len);
+					bvec.bv_offset, bv_len);
 		}
 
 		start = page_offset(page);
-		end = start + bvec.bv_offset
-			+ min_t(unsigned int, bvec.bv_len, PAGE_CACHE_SIZE) - 1;
-		len = bvec.bv_len;
+		end = start + bvec.bv_offset + bv_len - 1;
+		len = bv_len;
 
 		mirror = io_bio->mirror_num;
 		if (likely(uptodate && tree->ops &&

fs/btrfs/file-item.c

@@ -448,6 +448,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 	index = 0;
 
 	bio_for_each_page(bvec, bio, iter) {
+		unsigned int bv_len = min_t(unsigned int, bvec.bv_len, PAGE_CACHE_SIZE);
+
 		if (!contig)
 			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
 
@@ -472,14 +474,14 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 		sums->sums[index] = ~(u32)0;
 		sums->sums[index] = btrfs_csum_data(data + bvec.bv_offset,
 						    sums->sums[index],
-						    bvec.bv_len);
+						    bv_len);
 		kunmap_atomic(data);
 		btrfs_csum_final(sums->sums[index],
 				 (char *)(sums->sums + index));
 
 		index++;
-		offset += bvec.bv_len;
-		this_sum_bytes += bvec.bv_len;
+		offset += bv_len;
+		this_sum_bytes += bv_len;
 	}
 	this_sum_bytes = 0;
 	btrfs_add_ordered_sum(inode, ordered, sums);