fs/nfs/inode.c:1854 nfs_ooo_merge() error: testing array offset 'cnt' after use.

fs/nfs/inode.c:1854 nfs_ooo_merge() error: testing array offset 'cnt' after use.

[kernel test robot]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
CC: linux-kernel@vger.kernel.org
TO: NeilBrown <neilb@suse.de>
CC: Anna Schumaker <Anna.Schumaker@Netapp.com>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   2e1e1337881b0e9844d687982aa54b31b1269b11
commit: 3db63daabe210af32a09533fe7d8d47c711a103c NFSv3: handle out-of-order write replies.
date:   4 weeks ago
:::::: branch date: 6 hours ago
:::::: commit date: 4 weeks ago
config: x86_64-randconfig-m001-20230501 (https://download.01.org/0day-ci/archive/20230506/202305061623.JNCCAx1G-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Link: https://lore.kernel.org/r/202305061623.JNCCAx1G-lkp@intel.com/

smatch warnings:
fs/nfs/inode.c:1854 nfs_ooo_merge() error: testing array offset 'cnt' after use.

vim +/cnt +1854 fs/nfs/inode.c

7b24dacf084005 Trond Myklebust 2021-04-09  1820  
3db63daabe210a NeilBrown       2023-03-22  1821  static void nfs_ooo_merge(struct nfs_inode *nfsi,
3db63daabe210a NeilBrown       2023-03-22  1822  			  u64 start, u64 end)
3db63daabe210a NeilBrown       2023-03-22  1823  {
3db63daabe210a NeilBrown       2023-03-22  1824  	int i, cnt;
3db63daabe210a NeilBrown       2023-03-22  1825  
3db63daabe210a NeilBrown       2023-03-22  1826  	if (nfsi->cache_validity & NFS_INO_DATA_INVAL_DEFER)
3db63daabe210a NeilBrown       2023-03-22  1827  		/* No point merging anything */
3db63daabe210a NeilBrown       2023-03-22  1828  		return;
3db63daabe210a NeilBrown       2023-03-22  1829  
3db63daabe210a NeilBrown       2023-03-22  1830  	if (!nfsi->ooo) {
3db63daabe210a NeilBrown       2023-03-22  1831  		nfsi->ooo = kmalloc(sizeof(*nfsi->ooo), GFP_ATOMIC);
3db63daabe210a NeilBrown       2023-03-22  1832  		if (!nfsi->ooo) {
3db63daabe210a NeilBrown       2023-03-22  1833  			nfsi->cache_validity |= NFS_INO_DATA_INVAL_DEFER;
3db63daabe210a NeilBrown       2023-03-22  1834  			return;
3db63daabe210a NeilBrown       2023-03-22  1835  		}
3db63daabe210a NeilBrown       2023-03-22  1836  		nfsi->ooo->cnt = 0;
3db63daabe210a NeilBrown       2023-03-22  1837  	}
3db63daabe210a NeilBrown       2023-03-22  1838  
3db63daabe210a NeilBrown       2023-03-22  1839  	/* add this range, merging if possible */
3db63daabe210a NeilBrown       2023-03-22  1840  	cnt = nfsi->ooo->cnt;
3db63daabe210a NeilBrown       2023-03-22  1841  	for (i = 0; i < cnt; i++) {
3db63daabe210a NeilBrown       2023-03-22  1842  		if (end == nfsi->ooo->gap[i].start)
3db63daabe210a NeilBrown       2023-03-22  1843  			end = nfsi->ooo->gap[i].end;
3db63daabe210a NeilBrown       2023-03-22  1844  		else if (start == nfsi->ooo->gap[i].end)
3db63daabe210a NeilBrown       2023-03-22  1845  			start = nfsi->ooo->gap[i].start;
3db63daabe210a NeilBrown       2023-03-22  1846  		else
3db63daabe210a NeilBrown       2023-03-22  1847  			continue;
3db63daabe210a NeilBrown       2023-03-22  1848  		/* Remove 'i' from table and loop to insert the new range */
3db63daabe210a NeilBrown       2023-03-22  1849  		cnt -= 1;
3db63daabe210a NeilBrown       2023-03-22  1850  		nfsi->ooo->gap[i] = nfsi->ooo->gap[cnt];
3db63daabe210a NeilBrown       2023-03-22  1851  		i = -1;
3db63daabe210a NeilBrown       2023-03-22  1852  	}
3db63daabe210a NeilBrown       2023-03-22  1853  	if (start != end) {
3db63daabe210a NeilBrown       2023-03-22 @1854  		if (cnt >= ARRAY_SIZE(nfsi->ooo->gap)) {
3db63daabe210a NeilBrown       2023-03-22  1855  			nfsi->cache_validity |= NFS_INO_DATA_INVAL_DEFER;
3db63daabe210a NeilBrown       2023-03-22  1856  			kfree(nfsi->ooo);
3db63daabe210a NeilBrown       2023-03-22  1857  			nfsi->ooo = NULL;
3db63daabe210a NeilBrown       2023-03-22  1858  			return;
3db63daabe210a NeilBrown       2023-03-22  1859  		}
3db63daabe210a NeilBrown       2023-03-22  1860  		nfsi->ooo->gap[cnt].start = start;
3db63daabe210a NeilBrown       2023-03-22  1861  		nfsi->ooo->gap[cnt].end = end;
3db63daabe210a NeilBrown       2023-03-22  1862  		cnt += 1;
3db63daabe210a NeilBrown       2023-03-22  1863  	}
3db63daabe210a NeilBrown       2023-03-22  1864  	nfsi->ooo->cnt = cnt;
3db63daabe210a NeilBrown       2023-03-22  1865  }
3db63daabe210a NeilBrown       2023-03-22  1866  

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