linux-ext4 - [PATCH 13/28] ext4: ext4_xattr_value_same() should return false for external data

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Message-Id: <20170531081517.11438-13-tahsin@google.com>
Date:   Wed, 31 May 2017 01:15:02 -0700
From:   Tahsin Erdogan <tahsin@...gle.com>
To:     Jan Kara <jack@...e.com>, Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Dave Kleikamp <shaggy@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mark Fasheh <mfasheh@...sity.com>,
        Joel Becker <jlbec@...lplan.org>, Jens Axboe <axboe@...com>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Mike Christie <mchristi@...hat.com>,
        Fabian Frederick <fabf@...net.be>, linux-ext4@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, ocfs2-devel@....oracle.com,
        reiserfs-devel@...r.kernel.org, Tahsin Erdogan <tahsin@...gle.com>
Subject: [PATCH 13/28] ext4: ext4_xattr_value_same() should return false for external data

ext4_xattr_value_same() is used as a quick optimization in case the new
xattr value is identical to the previous value. When xattr value is
stored in a xattr inode the check becomes expensive so it is better to
just assume that they are not equal.

Signed-off-by: Tahsin Erdogan <tahsin@...gle.com>
---
 fs/ext4/xattr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 4dd8be16d175..681a9b5eefd8 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1428,6 +1428,9 @@ static int ext4_xattr_value_same(struct ext4_xattr_search *s,
 {
 	void *value;
 
+	/* When e_value_inum is set the value is stored externally. */
+	if (s->here->e_value_inum)
+		return 0;
 	if (le32_to_cpu(s->here->e_value_size) != i->value_len)
 		return 0;
 	value = ((void *)s->base) + le16_to_cpu(s->here->e_value_offs);
-- 
2.13.0.219.gdb65acc882-goog