Re: [PATCH] filemap: Handle error return from __filemap_get_folio()

[Dan Carpenter <dan.carpenter@linaro.org>]

> 1)  There is an existing check which complains if you have "if (p) "
>     where p can be an error pointer, but not NULL.  If I revert the fix,
>     I get the correct warning now.
> 
>     fs/afs/dir_edit.c:242 afs_edit_dir_add()
>     warn: 'folio0' is an error pointer or valid *NEW*

I ran the new code last night.  There was one more folio bug (but every
function in the call tree triggers a warning).

fs/nfs/dir.c:405 nfs_readdir_folio_get_locked() warn: 'folio' is an error pointer or valid
fs/nfs/dir.c:1000 nfs_readdir_folio_get_cached() warn: 'folio' is an error pointer or valid
fs/nfs/dir.c:1019 find_and_lock_cache_page() warn: 'desc->folio' is an error pointer or valid

Other new warnings.  Mostly harmless checks for NULL.
drivers/usb/host/max3421-hcd.c:1913 max3421_probe() warn: 'max3421_hcd->spi_thread' is an error pointer or valid
drivers/block/aoe/aoecmd.c:1259 aoe_ktstart() warn: 'task' is an error pointer or valid
drivers/target/target_core_fabric_configfs.c:482 target_fabric_make_np() warn: 'se_tpg_np' is an error pointer or valid
drivers/media/i2c/rdacm20.c:641 rdacm20_probe() warn: 'dev->sensor' is an error pointer or valid
drivers/net/ethernet/microchip/vcap/vcap_api_kunit.c:291 test_vcap_xn_rule_creator() warn: '__right' is an error pointer or valid
drivers/net/ethernet/microchip/vcap/vcap_api_kunit.c:1349 vcap_api_encode_rule_test() warn: '__right' is an error pointer or valid
fs/configfs/dir.c:1339 configfs_mkdir() warn: 'item' is an error pointer or valid
kernel/cgroup/cgroup.c:5542 css_create() warn: 'css' is an error pointer or valid
sound/soc/apple/mca.c:955 mca_pcm_new() warn: 'chan' is an error pointer or valid
sound/soc/apple/mca.c:961 mca_pcm_new() warn: 'chan' is an error pointer or valid
lib/test_kmod.c:320 try_one_request() warn: 'info->task_sync' is an error pointer or valid
lib/test_firmware.c:918 trigger_batched_requests_store() warn: 'req->task' is an error pointer or valid

False postives based on my .config:
fs/ceph/cache.c:100 ceph_fscache_register_fs() warn: 'fsc->fscache' is an error pointer or valid
fs/erofs/fscache.c:354 erofs_fscache_register_volume() warn: 'volume' is an error pointer or valid

False positive because of a bug in Smatch:
fs/overlayfs/readdir.c:906 ovl_dir_fsync() warn: 'realfile' is an error pointer or valid

regards,
dan carpenter