linux-ext4 - [PATCH 2/2] ext4: mark fc as ineligible using an handle in ext4_xattr

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Message-ID: <20240919093848.2330-3-luis.henriques@linux.dev>
Date: Thu, 19 Sep 2024 10:38:48 +0100
From: "Luis Henriques (SUSE)" <luis.henriques@...ux.dev>
To: Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger@...ger.ca>,
	Jan Kara <jack@...e.cz>,
	Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Luis Henriques (SUSE)" <luis.henriques@...ux.dev>
Subject: [PATCH 2/2] ext4: mark fc as ineligible using an handle in ext4_xattr_set()

Calling ext4_fc_mark_ineligible() with a NULL handle is racy and may result
in a fast-commit being done before the filesystem is effectively marked as
ineligible.  This patch reduces the risk of this happening in function
ext4_xattr_set() by using an handle if one is available.

Suggested-by: Jan Kara <jack@...e.cz>
Signed-off-by: Luis Henriques (SUSE) <luis.henriques@...ux.dev>
---
 fs/ext4/xattr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 46ce2f21fef9..dbe4d11cd332 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2554,11 +2554,15 @@ ext4_xattr_set(struct inode *inode, int name_index, const char *name,
 	handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits);
 	if (IS_ERR(handle)) {
 		error = PTR_ERR(handle);
+		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_XATTR,
+					NULL);
 	} else {
 		int error2;
 
 		error = ext4_xattr_set_handle(handle, inode, name_index, name,
 					      value, value_len, flags);
+		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_XATTR,
+					handle);
 		error2 = ext4_journal_stop(handle);
 		if (error == -ENOSPC &&
 		    ext4_should_retry_alloc(sb, &retries))
@@ -2566,7 +2570,6 @@ ext4_xattr_set(struct inode *inode, int name_index, const char *name,
 		if (error == 0)
 			error = error2;
 	}
-	ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_XATTR, NULL);
 
 	return error;
 }