Documentation/filesystems/path-lookup.txt

1 Path walking and name lookup locking
9 path string. Then repeating the lookup from the child dentry and finding its
16 Prior to 2.5.10, dcache_lock was acquired in d_lookup (dcache hash lookup) and
50 current->fs->cwd or current->fs->root) as the first parent of the lookup. Then
53 parent for the next lookup.
58 Turning the child into a parent for the next lookup requires more checks and
72 - lookup and create missing parts of the path on demand.
77 Dcache name lookup
79 In order to lookup a dcache (parent, name) tuple, we take a hash on the tuple
115 lookup of the old list veering off into the new (incorrect) list and missing
121 lookup can be retried.
161 Because we didn't wait for a grace period, there may be a concurrent lookup
166 lookup operations. If a file is renamed from 'A' to 'B', a lookup must only
167 find either 'A' or 'B'. So if a lookup of 'A' returns NULL, a subsequent lookup
171 hash list, a lookup may find neither 'A' nor 'B' matching the dentry. The same
173 retrying a negative lookup result if a rename was in progress.
199 lookup which does not increment the refcount on the dentry or write to
203 Inodes are also rcu freed, so the seqcount lookup dentry's inode may also be
217 lookups, and can perform lookup of intermediate elements without any stores to
222 [*] RCU is still used for the dentry hash lookup in ref-walk, but not the full
254     | name:    "home"     |   hash lookup, then note d_seq and compare name
260     +---------------------+   Note: if dentry0 is now modified, lookup is
314   of the path lookup in ref-walk mode. -ECHILD tends to be used (for want of
340 The following table gives rcu lookup statistics for a few simple workloads
342 drop rcu that fail due to d_seq failure and requiring the entire path lookup
382 3. path-lookup.md in this directory.