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Currently the guestfs_readdir() API can not list long directories, due to it sending back the whole directory listing in a single guestfs protocol response, which is limited to GUESTFS_MESSAGE_MAX (approx. 4MB) in size. Introduce the "internal_readdir" action, for transferring the directory listing from the daemon to the library through a FileOut parameter. Rewrite guestfs_readdir() on top of this new internal function: - The new "internal_readdir" action is a daemon action. Do not repurpose the "readdir" proc_nr (138) for "internal_readdir", as some distros ship the binary appliance to their users, and reusing the proc_nr could create a mismatch between library & appliance with obscure symptoms. Replace the old proc_nr (138) with a new proc_nr (511) instead; a mismatch would then produce a clear error message. Assume the new action will first be released in libguestfs-1.48.2. - Turn "readdir" from a daemon action into a non-daemon one. Call the daemon action guestfs_internal_readdir() manually, receive the FileOut parameter into a temp file, then deserialize the dirents array from the temp file. This patch sneakily fixes an independent bug, too. In the pre-patch do_readdir() function [daemon/readdir.c], when readdir() returns NULL, we don't distinguish "end of directory stream" from "readdir() failed". This rewrite fixes this problem -- I didn't see much value separating out the fix for the original do_readdir(). Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1674392 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Message-Id: <20220502085601.15012-2-lersek@redhat.com> Reviewed-by: Richard W.M. Jones <rjones@redhat.com>