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Message-ID: <a14347d2-6189-49bc-a1cc-e5959e76e6c2@ghiti.fr>
Date: Mon, 17 Feb 2025 13:06:49 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Christoph Hellwig <hch@....de>, kernel test robot <lkp@...el.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
Carlos Maiolino <cem@...nel.org>, "Darrick J. Wong" <djwong@...nel.org>,
linux-riscv@...ts.infradead.org
Subject: Re: fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is
never less than zero.
Hi Christoph,
On 17/02/2025 10:24, Christoph Hellwig wrote:
> On Mon, Feb 17, 2025 at 01:53:08PM +0800, kernel test robot wrote:
>> New smatch warnings:
>> fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is never less than zero.
> Looks like this is an issue in the riscv virt_to_page implementation
> which also shows up in various other places. Any chance this could get
> fixed in the riscv code?
To me, the only test that could give rise to this warning is the last
part of:
#define is_linear_mapping(x) \
((x) >= PAGE_OFFSET && (!IS_ENABLED(CONFIG_64BIT) || (x) <
PAGE_OFFSET + KERN_VIRT_SIZE))
But given that the config is a 32-bit config, it should not be evaluated
at all.
Could that be a false-positive and then an issue in smatch?
Thanks,
Alex
>
>> Old smatch warnings:
>> fs/xfs/xfs_linux.h:283 kmem_to_page() warn: unsigned '_x' is never less than zero.
>> fs/xfs/xfs_buf.c:761 xfs_buf_get_map() error: we previously assumed 'bp' could be null (see line 743)
>> arch/riscv/include/asm/atomic.h:218 arch_atomic_fetch_add_unless() warn: inconsistent indenting
>>
>> vim +/_x +1534 fs/xfs/xfs_buf.c
>>
>> 1518
>> 1519 static void
>> 1520 xfs_buf_submit_bio(
>> 1521 struct xfs_buf *bp)
>> 1522 {
>> 1523 unsigned int size = BBTOB(bp->b_length);
>> 1524 unsigned int map = 0, p;
>> 1525 struct blk_plug plug;
>> 1526 struct bio *bio;
>> 1527
>> 1528 bio = bio_alloc(bp->b_target->bt_bdev, bp->b_page_count,
>> 1529 xfs_buf_bio_op(bp), GFP_NOIO);
>> 1530 bio->bi_private = bp;
>> 1531 bio->bi_end_io = xfs_buf_bio_end_io;
>> 1532
>> 1533 if (bp->b_flags & _XBF_KMEM) {
>>> 1534 __bio_add_page(bio, virt_to_page(bp->b_addr), size,
>> 1535 bp->b_offset);
>> 1536 } else {
>> 1537 for (p = 0; p < bp->b_page_count; p++)
>> 1538 __bio_add_page(bio, bp->b_pages[p], PAGE_SIZE, 0);
>> 1539 bio->bi_iter.bi_size = size; /* limit to the actual size used */
>> 1540
>> 1541 if (xfs_buf_is_vmapped(bp))
>> 1542 flush_kernel_vmap_range(bp->b_addr,
>> 1543 xfs_buf_vmap_len(bp));
>> 1544 }
>> 1545
>> 1546 /*
>> 1547 * If there is more than one map segment, split out a new bio for each
>> 1548 * map except of the last one. The last map is handled by the
>> 1549 * remainder of the original bio outside the loop.
>> 1550 */
>> 1551 blk_start_plug(&plug);
>> 1552 for (map = 0; map < bp->b_map_count - 1; map++) {
>> 1553 struct bio *split;
>> 1554
>> 1555 split = bio_split(bio, bp->b_maps[map].bm_len, GFP_NOFS,
>> 1556 &fs_bio_set);
>> 1557 split->bi_iter.bi_sector = bp->b_maps[map].bm_bn;
>> 1558 bio_chain(split, bio);
>> 1559 submit_bio(split);
>> 1560 }
>> 1561 bio->bi_iter.bi_sector = bp->b_maps[map].bm_bn;
>> 1562 submit_bio(bio);
>> 1563 blk_finish_plug(&plug);
>> 1564 }
>> 1565
>>
>> --
>> 0-DAY CI Kernel Test Service
>> https://github.com/intel/lkp-tests/wiki
> ---end quoted text---
>
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