linux-kernel - [PATCH 2/8] bcachefs: Add comments for inode snapshot requirements

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Message-ID: <20250502200002.1309862-3-kent.overstreet@linux.dev>
Date: Fri,  2 May 2025 15:59:54 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH 2/8] bcachefs: Add comments for inode snapshot requirements

Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
---
 fs/bcachefs/io_write.c | 6 ++++++
 fs/bcachefs/xattr.c    | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/fs/bcachefs/io_write.c b/fs/bcachefs/io_write.c
index add141ac45b5..399df8fede8b 100644
--- a/fs/bcachefs/io_write.c
+++ b/fs/bcachefs/io_write.c
@@ -279,6 +279,12 @@ static inline int bch2_extent_update_i_size_sectors(struct btree_trans *trans,
 		inode_update_flags = 0;
 	}
 
+	/*
+	 * extents, dirents and xattrs updates require that an inode update also
+	 * happens - to ensure that if a key exists in one of those btrees with
+	 * a given snapshot ID an inode is also present - so we may have to skip
+	 * the nojournal optimization:
+	 */
 	if (inode->k.p.snapshot != iter.snapshot) {
 		inode->k.p.snapshot = iter.snapshot;
 		inode_update_flags = 0;
diff --git a/fs/bcachefs/xattr.c b/fs/bcachefs/xattr.c
index b8bc2fb04f15..ea3f87f6fe49 100644
--- a/fs/bcachefs/xattr.c
+++ b/fs/bcachefs/xattr.c
@@ -176,6 +176,11 @@ int bch2_xattr_set(struct btree_trans *trans, subvol_inum inum,
 	if (ret)
 		return ret;
 
+	/*
+	 * Besides the ctime update, extents, dirents and xattrs updates require
+	 * that an inode update also happens - to ensure that if a key exists in
+	 * one of those btrees with a given snapshot ID an inode is also present
+	 */
 	inode_u->bi_ctime = bch2_current_time(c);
 
 	ret = bch2_inode_write(trans, &inode_iter, inode_u);
-- 
2.49.0