[PATCH 6.6.y] erofs: add sysfs feature entry for xattr prefixes

[Sasha Levin <sashal@kernel.org>]

From: Jingbo Xu <jefflexu@linux.alibaba.com>

[ Upstream commit 839f075aabdf5c21048f9801b87c0b841dd3d064 ]

Let /sys/fs/erofs/features/xattr_prefixes advertise that this kernel
supports the EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES on-disk format.

Fixes: 6a318ccd7e08 ("erofs: enable long extended attribute name prefixes")
Cc: stable@vger.kernel.org # 6.4+
Reviewed-by: Gao Xiang <xiang@kernel.org>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Gao Xiang <xiang@kernel.org>
[ adjusted feature-list context for missing 48bit and metabox entries while retaining zero_padding. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Documentation/ABI/testing/sysfs-fs-erofs | 2 +-
 fs/erofs/sysfs.c                         | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
index 284224d1b56fe..2997379bf8044 100644
--- a/Documentation/ABI/testing/sysfs-fs-erofs
+++ b/Documentation/ABI/testing/sysfs-fs-erofs
@@ -5,7 +5,7 @@ Description:	Shows all enabled kernel features.
 		Supported features:
 		zero_padding, compr_cfgs, big_pcluster, chunked_file,
 		device_table, compr_head2, sb_chksum, ztailpacking,
-		dedupe, fragments.
+		dedupe, fragments, xattr_prefixes.
 
 What:		/sys/fs/erofs/<disk>/sync_decompress
 Date:		November 2021
diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index 435e515c07920..92f0bc13623cc 100644
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -78,6 +78,7 @@ EROFS_ATTR_FEATURE(sb_chksum);
 EROFS_ATTR_FEATURE(ztailpacking);
 EROFS_ATTR_FEATURE(fragments);
 EROFS_ATTR_FEATURE(dedupe);
+EROFS_ATTR_FEATURE(xattr_prefixes);
 
 static struct attribute *erofs_feat_attrs[] = {
 	ATTR_LIST(zero_padding),
@@ -90,6 +91,7 @@ static struct attribute *erofs_feat_attrs[] = {
 	ATTR_LIST(ztailpacking),
 	ATTR_LIST(fragments),
 	ATTR_LIST(dedupe),
+	ATTR_LIST(xattr_prefixes),
 	NULL,
 };
 ATTRIBUTE_GROUPS(erofs_feat);
-- 
2.53.0