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authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:27 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:19 +1100
commit621e155a3591962420eacdd39f6f0aa29ceb221e (patch)
tree387a9fb396f1bf24514b712c294182e36ba51076 /Documentation/filesystems/porting
parentfb2d5b86aff355a27ebfc132d3c99f4a940cc3fe (diff)
fs: change d_compare for rcu-walk
Change d_compare so it may be called from lock-free RCU lookups. This does put significant restrictions on what may be done from the callback, however there don't seem to have been any problems with in-tree fses. If some strange use case pops up that _really_ cannot cope with the rcu-walk rules, we can just add new rcu-unaware callbacks, which would cause name lookup to drop out of rcu-walk mode. For in-tree filesystems, this is just a mechanical change. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Diffstat (limited to 'Documentation/filesystems/porting')
-rw-r--r--Documentation/filesystems/porting7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 9e71c9ad310..d44511e2082 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -326,3 +326,10 @@ to it.
unreferenced dentries, and is now only called when the dentry refcount goes to
0. Even on 0 refcount transition, it must be able to tolerate being called 0,
1, or more times (eg. constant, idempotent).
+
+---
+[mandatory]
+
+ .d_compare() calling convention and locking rules are significantly
+changed. Read updated documentation in Documentation/filesystems/vfs.txt (and
+look at examples of other filesystems) for guidance.