CVS: cvs.openbsd.org: src

CVSROOT:	/cvs
Module name:	src
Changes by:	[email protected]	2026/08/04 09:20:28

Modified files:
	lib/libfuse    : fuse_ops.c fuse_private.h 

Log message:
When using the high-level FUSE API, the filesystem may choose between
two modes of operation when implementing readdir().

1) The readdir implementation ignores the offset parameter, and
passes zero to the filler function's offset. The filler function
will not return '1' (unless an error happens), so the whole
directory is read in a single readdir operation.

2) The readdir implementation keeps track of the offsets of the
directory entries. It uses the offset parameter and always passes
non-zero offset to the filler function. When the buffer is full
(or an error happens) the filler function will return '1'.

We currently don't support 1) and instead implement an alternative
mode that is stateless but emulates the behaviour. For each
FUSE_READDIR received from the kernel, it will invoke the file
system's readdir() callback and ask it to completely fill the buffer
again, but ignore any entries that are before the given offset or
exceed the size of the buffer. This of course has a performance
penalty.

This change introduces a stateful buffer that is filled by the file
system on the first FUSE_READDIR message and then read from on
subsequent FUSE_READDIR messages on the same directory vnode until
FUSE_RELEASEDIR is received.

If a 0 offset is passed to readdir, then the buffer is refreshed.
This ensures that the buffer does not become stale when the file
handle remains open due to the directory being the current directory
for a process.