Hello David Howells,
The patch 62ab63352350: "fscache: Implement volume registration" from
Oct 20, 2021, leads to the following Smatch static checker warning:
fs/fscache/volume.c:420 fscache_put_volume()
warn: sleeping in atomic context
fs/fscache/volume.c
409 void fscache_put_volume(struct fscache_volume *volume,
410 enum fscache_volume_trace where)
411 {
412 if (volume) {
413 unsigned int debug_id = volume->debug_id;
414 bool zero;
415 int ref;
416
417 zero = __refcount_dec_and_test(&volume->ref, &ref);
418 trace_fscache_volume(debug_id, ref - 1, where);
419 if (zero)
--> 420 fscache_free_volume(volume);
fscache_free_volume() calls down_write() which sleeps.
421 }
422 }
The more difficult thing to explain is how this is called with preempt
disabled. According to Smatch there are lots of callers which disable
preempt. I have included the complete list at the end, all the
places marked as "disables preempt" apparently have a call tree from
there to fscache_put_volume().
But I have cleaned up one call tree here.
cachefiles_withdraw_objects() <- disables preempt
-> fscache_withdraw_cookie()
-> fscache_drop_withdraw_cookie()
-> fscache_cookie_drop_from_lru()
-> fscache_put_cookie()
-> fscache_put_volume()
regards,
dan carpenter
nfs_inode_set_delegation() <- disables preempt
alloc_nfs_open_dir_context() <- disables preempt
nfs_mark_dir_for_revalidate() <- disables preempt
nfs_drop_nlink() <- disables preempt
nfs_rename() <- disables preempt
nfs_zap_caches() <- disables preempt
nfs_set_inode_stale() <- disables preempt
nfs_setattr_update_inode() <- disables preempt
nfs_refresh_inode() <- disables preempt
nfs_post_op_update_inode() <- disables preempt
nfs_post_op_update_inode_force_wcc() <- disables preempt
nfs_writeback_update_inode() <- disables preempt
-> nfs_post_op_update_inode_force_wcc_locked()
-> nfs_post_op_update_inode_locked()
-> nfs_refresh_inode_locked()
-> nfs_update_inode()
-> nfs_set_inode_stale_locked()
-> nfs_zap_caches_locked()
nfs_zap_mapping() <- disables preempt
nfs_invalidate_atime() <- disables preempt
nfs_setattr_update_inode() <- disables preempt <duplicate>
nfs_inode_attach_open_context() <- disables preempt
nfs_update_inode() <duplicate>
-> nfs_wcc_update_inode()
nfs_refresh_inode_locked() <duplicate>
-> nfs_check_inode_attributes()
nfs_post_op_update_inode_locked() <duplicate>
nfs_update_inode() <duplicate>
nfs4_inc_nlink() <- disables preempt
nfs4_do_create() <- disables preempt
-> nfs4_inc_nlink_locked()
_nfs4_proc_remove() <- disables preempt
-> nfs4_dec_nlink_locked()
nfs4_update_changeattr() <- disables preempt
_nfs4_proc_remove() <- disables preempt <duplicate>
nfs4_do_create() <- disables preempt <duplicate>
-> nfs4_update_changeattr_locked()
__nfs4_proc_set_acl() <- disables preempt
_nfs42_proc_fallocate() <- disables preempt
nfs42_copy_dest_done() <- disables preempt
nfs_sillyrename() <- disables preempt
nfs_set_pageerror() <- disables preempt
nfs_writeback_done() <- disables preempt
-> nfs_set_cache_invalid()
-> nfs_fscache_invalidate()
-> fscache_invalidate()
-> __fscache_invalidate() <- disables preempt
-> fscache_begin_cookie_access()
fscache_cookie_state_machine() <- disables preempt
-> fscache_end_cookie_access()
cachefiles_withdraw_objects() <- disables preempt
-> fscache_withdraw_cookie()
-> fscache_drop_withdraw_cookie()
-> __fscache_withdraw_cookie()
__fscache_invalidate() <duplicate>
-> fscache_queue_cookie()
-> __fscache_queue_cookie()
fscache_drop_withdraw_cookie() <duplicate>
-> fscache_cookie_drop_from_lru()
-> fscache_put_cookie()
-> fscache_put_volume()
--
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