From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boaz Harrosh Subject: Re: [PATCHv5 10/16] exofs: fix race condition in marking SB dirty Date: Sun, 06 Jun 2010 19:12:41 +0300 Message-ID: <4C0BC8F9.2050306@panasas.com> References: <1275835829-1478-1-git-send-email-dedekind1@gmail.com> <1275835829-1478-11-git-send-email-dedekind1@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Al Viro , Andrew Morton , LKML , linux-fsdevel@vger.kernel.org, Artem Bityutskiy To: Artem Bityutskiy Return-path: In-Reply-To: <1275835829-1478-11-git-send-email-dedekind1@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 06/06/2010 05:50 PM, Artem Bityutskiy wrote: > From: Artem Bityutskiy > > When synchronizing the superblock, exofs first initiates the SB write > (a) and then marks the superblock as clean (b). However, meanwhile > (between (a) and (b)) someone else can modify the superblock and > mark it as dirty. This would be a race condition, and the result > would be that we'd end up with a modified superblock which would > nevertheless be marked as clean (because of (b)). This means that > 'sync_supers()' would never call our '->write_super()', at least > not until yet another SB change happens. > > This patch fixes this race condition by marking the superblock as > clean before initiating the write operation. > > Signed-off-by: Artem Bityutskiy > Cc: Boaz Harrosh Ack-by: Boaz Harrosh Grate fix thanks Boaz > --- > fs/exofs/super.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/fs/exofs/super.c b/fs/exofs/super.c > index 74ccbdc..0b432b9 100644 > --- a/fs/exofs/super.c > +++ b/fs/exofs/super.c > @@ -219,6 +219,7 @@ int exofs_sync_fs(struct super_block *sb, int wait) > * the fscb->s_dev_table_oid member. There is no read-modify-write > * here. > */ > + sb_mark_clean(sb); > ios->length = offsetof(struct exofs_fscb, s_dev_table_oid); > memset(fscb, 0, ios->length); > fscb->s_nextid = cpu_to_le64(sbi->s_nextid); > @@ -237,7 +238,6 @@ int exofs_sync_fs(struct super_block *sb, int wait) > EXOFS_ERR("%s: exofs_sbi_write failed.\n", __func__); > goto out; > } > - sb_mark_clean(sb); > > out: > EXOFS_DBGMSG("s_nextid=0x%llx ret=%d\n", _LLU(sbi->s_nextid), ret);