linux-kernel - [PATCH 35/42] ext4: fix xattr deadlock

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Message-Id: <1223525160-9887-36-git-send-email-tytso@mit.edu>
Date:	Thu,  9 Oct 2008 00:05:53 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Kalpak Shah <kalpak.shah@....com>, "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 35/42] ext4: fix xattr deadlock

From: Kalpak Shah <kalpak.shah@....com>

ext4_xattr_set_handle() eventually ends up calling
ext4_mark_inode_dirty() which tries to expand the inode by shifting
the EAs.  This leads to the xattr_sem being downed again and leading
to a deadlock.

This patch makes sure that if ext4_xattr_set_handle() is in the
call-chain, ext4_mark_inode_dirty() will not expand the inode.

Signed-off-by: Kalpak Shah <kalpak.shah@....com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
 fs/ext4/xattr.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 8954208..362b0ed 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -959,6 +959,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
 	struct ext4_xattr_block_find bs = {
 		.s = { .not_found = -ENODATA, },
 	};
+	unsigned long no_expand;
 	int error;
 
 	if (!name)
@@ -966,6 +967,9 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
 	if (strlen(name) > 255)
 		return -ERANGE;
 	down_write(&EXT4_I(inode)->xattr_sem);
+	no_expand = EXT4_I(inode)->i_state & EXT4_STATE_NO_EXPAND;
+	EXT4_I(inode)->i_state |= EXT4_STATE_NO_EXPAND;
+
 	error = ext4_get_inode_loc(inode, &is.iloc);
 	if (error)
 		goto cleanup;
@@ -1042,6 +1046,8 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
 cleanup:
 	brelse(is.iloc.bh);
 	brelse(bs.bh);
+	if (no_expand == 0)
+		EXT4_I(inode)->i_state &= ~EXT4_STATE_NO_EXPAND;
 	up_write(&EXT4_I(inode)->xattr_sem);
 	return error;
 }
-- 
1.5.6.1.205.ge2c7.dirty

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