From 2daf18a7884dc03d5164ab9c7dc3f2ea70638469 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 8 Aug 2023 21:33:56 -0700 Subject: tmpfs,xattr: enable limited user extended attributes Enable "user." extended attributes on tmpfs, limiting them by tracking the space they occupy, and deducting that space from the limited ispace (unless tmpfs mounted with nr_inodes=0 to leave that ispace unlimited). tmpfs inodes and simple xattrs are both unswappable, and have to be in lowmem on a 32-bit highmem kernel: so the ispace limit is appropriate for xattrs, without any need for a further mount option. Add simple_xattr_space() to give approximate but deterministic estimate of the space taken up by each xattr: with simple_xattrs_free() outputting the space freed if required (but kernfs and even some tmpfs usages do not require that, so don't waste time on strlen'ing if not needed). Security and trusted xattrs were already supported: for consistency and simplicity, account them from the same pool; though there's a small risk that a tmpfs with enough space before would now be considered too small. When extended attributes are used, "df -i" does show more IUsed and less IFree than can be explained by the inodes: document that (manpage later). xfstests tests/generic which were not run on tmpfs before but now pass: 020 037 062 070 077 097 103 117 337 377 454 486 523 533 611 618 728 with no new failures. Signed-off-by: Hugh Dickins Reviewed-by: Jan Kara Reviewed-by: Carlos Maiolino Message-Id: <2e63b26e-df46-5baa-c7d6-f9a8dd3282c5@google.com> Signed-off-by: Christian Brauner --- fs/Kconfig | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/Kconfig') diff --git a/fs/Kconfig b/fs/Kconfig index 8218a71933f9..7da21f563192 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -205,8 +205,8 @@ config TMPFS_XATTR Extended attributes are name:value pairs associated with inodes by the kernel or by users (see the attr(5) manual page for details). - Currently this enables support for the trusted.* and - security.* namespaces. + This enables support for the trusted.*, security.* and user.* + namespaces. You need this for POSIX ACL support on tmpfs. -- cgit v1.2.3