Re: [PATCH v2 13/13] mm: zswap: Compress batching with Intel IAA in zswap_store() of large folios.

[Dan Carpenter]

Hi Kanchana,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Kanchana-P-Sridhar/crypto-acomp-Define-two-new-interfaces-for-compress-decompress-batching/20241103-112337
base:   5c4cf96cd70230100b5d396d45a5c9a332539d19
patch link:    https://lore.kernel.org/r/20241103032111.333282-14-kanchana.p.sridhar%40intel.com
patch subject: [PATCH v2 13/13] mm: zswap: Compress batching with Intel IAA in zswap_store() of large folios.
config: x86_64-randconfig-161-20241104 (https://download.01.org/0day-ci/archive/20241104/202411040859.2z0MfFkR-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202411040859.2z0MfFkR-lkp@xxxxxxxxx/

smatch warnings:
mm/zswap.c:1788 zswap_store_propagate_errors() warn: variable dereferenced before check 'sbp->entry' (see line 1785)

vim +1788 mm/zswap.c

c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1771  static __always_inline void zswap_store_propagate_errors(
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1772  	struct zswap_store_pipeline_state *zst,
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1773  	u8 error_batch_idx)
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1774  {
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1775  	u8 i;
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1776  
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1777  	if (zst->errors[error_batch_idx])
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1778  		return;
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1779  
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1780  	for (i = 0; i < zst->nr_comp_pages; ++i) {
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1781  		struct zswap_store_sub_batch_page *sbp = &zst->sub_batch[i];
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1782  
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1783  		if (sbp->batch_idx == error_batch_idx) {
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1784  			if (!sbp->error) {
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02 @1785  				if (!IS_ERR_VALUE(sbp->entry->handle))
                                                                                                  ^^^^^^^^^^^^^^^^^^
Dereferenced

c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1786  					zpool_free(zst->pool->zpool, sbp->entry->handle);
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1787  
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02 @1788  				if (sbp->entry) {
                                                                                    ^^^^^^^^^^
Checked too late

c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1789  					zswap_entry_cache_free(sbp->entry);
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1790  					sbp->entry = NULL;
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1791  				}
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1792  				sbp->error = -EINVAL;
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1793  			}
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1794  		}
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1795  	}
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1796  
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1797  	/*
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1798  	 * Set zswap status for the folio to "error"
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1799  	 * for use in swap_writepage.
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1800  	 */
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1801  	zst->errors[error_batch_idx] = -EINVAL;
c1252ac91d6a6a Kanchana P Sridhar 2024-11-02  1802  }

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