Mention atomic_o_trunc capability in description of open() handler.

diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index bad1d45f9a2f723b57a15c277bdb700de2431c2c..0f8c030d836b9831e50f7a06a4434620dcb08ecd 100644 (file)
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -420,12 +420,18 @@ struct fuse_lowlevel_ops {
        /**
         * Open a file
         *
-        * Open flags (with the exception of O_CREAT, O_EXCL, O_NOCTTY and
-        * O_TRUNC) are available in fi->flags.
-        *
-        * Filesystem may store an arbitrary file handle (pointer, index,
-        * etc) in fi->fh, and use this in other all other file operations
-        * (read, write, flush, release, fsync).
+        * Open flags are available in fi->flags.  Creation (O_CREAT,
+        * O_EXCL, O_NOCTTY) and by default also truncation (O_TRUNC)
+        * flags will be filtered out. If an application specifies
+        * O_TRUNC, fuse first calls truncate() and then open().
+        *
+        * If filesystem is able to handle O_TRUNC directly, the
+        * init() handler should set the `FUSE_CAP_ATOMIC_O_TRUNC` bit
+        * in ``conn->want``.
+        *
+        * Filesystem may store an arbitrary file handle (pointer,
+        * index, etc) in fi->fh, and use this in other all other file
+        * operations (read, write, flush, release, fsync).
         *
         * Filesystem may also implement stateless file I/O and not store
         * anything in fi->fh.