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    SubjectRe: [PATCHv5 10/16] exofs: fix race condition in marking SB dirty
    On 06/06/2010 05:50 PM, Artem Bityutskiy wrote:
    > From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
    >
    > 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 <Artem.Bityutskiy@nokia.com>
    > Cc: Boaz Harrosh <bharrosh@panasas.com>

    Ack-by: Boaz Harrosh <bharrosh@panasas.com>

    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);



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