linux-kernel - fs/buffer.c:2254:5: warning: stack frame size (2128) exceeds limit (1024) in 'block_read_full

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Message-ID: <202212042048.pOSIGbqr-lkp@intel.com>
Date:   Sun, 4 Dec 2022 20:52:45 +0800
From:   kernel test robot <lkp@...el.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: fs/buffer.c:2254:5: warning: stack frame size (2128) exceeds limit
 (1024) in 'block_read_full_folio'

Hi Matthew,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   c2bf05db6c78f53ca5cd4b48f3b9b71f78d215f1
commit: 2c69e2057962b6bd76d72446453862eb59325b49 fs: Convert block_read_full_page() to block_read_full_folio()
date:   7 months ago
config: hexagon-randconfig-r024-20221204
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 6e4cea55f0d1104408b26ac574566a0e4de48036)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2c69e2057962b6bd76d72446453862eb59325b49
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 2c69e2057962b6bd76d72446453862eb59325b49
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> fs/buffer.c:2254:5: warning: stack frame size (2128) exceeds limit (1024) in 'block_read_full_folio' [-Wframe-larger-than]
   int block_read_full_folio(struct folio *folio, get_block_t *get_block)
       ^
   69/2128 (3.24%) spills, 2059/2128 (96.76%) variables
   1 warning generated.


vim +/block_read_full_folio +2254 fs/buffer.c

  2246	
  2247	/*
  2248	 * Generic "read_folio" function for block devices that have the normal
  2249	 * get_block functionality. This is most of the block device filesystems.
  2250	 * Reads the folio asynchronously --- the unlock_buffer() and
  2251	 * set/clear_buffer_uptodate() functions propagate buffer state into the
  2252	 * folio once IO has completed.
  2253	 */
> 2254	int block_read_full_folio(struct folio *folio, get_block_t *get_block)
  2255	{
  2256		struct inode *inode = folio->mapping->host;
  2257		sector_t iblock, lblock;
  2258		struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
  2259		unsigned int blocksize, bbits;
  2260		int nr, i;
  2261		int fully_mapped = 1;
  2262	
  2263		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
  2264	
  2265		head = create_page_buffers(&folio->page, inode, 0);
  2266		blocksize = head->b_size;
  2267		bbits = block_size_bits(blocksize);
  2268	
  2269		iblock = (sector_t)folio->index << (PAGE_SHIFT - bbits);
  2270		lblock = (i_size_read(inode)+blocksize-1) >> bbits;
  2271		bh = head;
  2272		nr = 0;
  2273		i = 0;
  2274	
  2275		do {
  2276			if (buffer_uptodate(bh))
  2277				continue;
  2278	
  2279			if (!buffer_mapped(bh)) {
  2280				int err = 0;
  2281	
  2282				fully_mapped = 0;
  2283				if (iblock < lblock) {
  2284					WARN_ON(bh->b_size != blocksize);
  2285					err = get_block(inode, iblock, bh, 0);
  2286					if (err)
  2287						folio_set_error(folio);
  2288				}
  2289				if (!buffer_mapped(bh)) {
  2290					folio_zero_range(folio, i * blocksize,
  2291							blocksize);
  2292					if (!err)
  2293						set_buffer_uptodate(bh);
  2294					continue;
  2295				}
  2296				/*
  2297				 * get_block() might have updated the buffer
  2298				 * synchronously
  2299				 */
  2300				if (buffer_uptodate(bh))
  2301					continue;
  2302			}
  2303			arr[nr++] = bh;
  2304		} while (i++, iblock++, (bh = bh->b_this_page) != head);
  2305	
  2306		if (fully_mapped)
  2307			folio_set_mappedtodisk(folio);
  2308	
  2309		if (!nr) {
  2310			/*
  2311			 * All buffers are uptodate - we can set the folio uptodate
  2312			 * as well. But not if get_block() returned an error.
  2313			 */
  2314			if (!folio_test_error(folio))
  2315				folio_mark_uptodate(folio);
  2316			folio_unlock(folio);
  2317			return 0;
  2318		}
  2319	
  2320		/* Stage two: lock the buffers */
  2321		for (i = 0; i < nr; i++) {
  2322			bh = arr[i];
  2323			lock_buffer(bh);
  2324			mark_buffer_async_read(bh);
  2325		}
  2326	
  2327		/*
  2328		 * Stage 3: start the IO.  Check for uptodateness
  2329		 * inside the buffer lock in case another process reading
  2330		 * the underlying blockdev brought it uptodate (the sct fix).
  2331		 */
  2332		for (i = 0; i < nr; i++) {
  2333			bh = arr[i];
  2334			if (buffer_uptodate(bh))
  2335				end_buffer_async_read(bh, 1);
  2336			else
  2337				submit_bh(REQ_OP_READ, 0, bh);
  2338		}
  2339		return 0;
  2340	}
  2341	EXPORT_SYMBOL(block_read_full_folio);
  2342	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

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