Documentation,ovl: document new file descriptor based layers

Add a minimal example how to specify layers via file descriptors.

Link: https://lore.kernel.org/r/20241014-work-overlayfs-v3-3-32b3fed1286e@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-10-14 11:40:58 +02:00
parent a08557d19e
commit a89ed67d3c
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@ -440,6 +440,23 @@ For example::
fsconfig(fs_fd, FSCONFIG_SET_STRING, "datadir+", "/do2", 0);
Specifying layers via file descriptors
--------------------------------------
Since kernel v6.13, overlayfs supports specifying layers via file descriptors in
addition to specifying them as paths. This feature is available for the
"datadir+", "lowerdir+", "upperdir", and "workdir+" mount options with the
fsconfig syscall from the new mount api::
fsconfig(fs_fd, FSCONFIG_SET_FD, "lowerdir+", NULL, fd_lower1);
fsconfig(fs_fd, FSCONFIG_SET_FD, "lowerdir+", NULL, fd_lower2);
fsconfig(fs_fd, FSCONFIG_SET_FD, "lowerdir+", NULL, fd_lower3);
fsconfig(fs_fd, FSCONFIG_SET_FD, "datadir+", NULL, fd_data1);
fsconfig(fs_fd, FSCONFIG_SET_FD, "datadir+", NULL, fd_data2);
fsconfig(fs_fd, FSCONFIG_SET_FD, "workdir", NULL, fd_work);
fsconfig(fs_fd, FSCONFIG_SET_FD, "upperdir", NULL, fd_upper);
fs-verity support
-----------------