On Sat 06-06-09 11:07:25, Wu Fengguang wrote:
> 1) I_FREEING tests should be coupled with I_CLEAR
>
> The two I_FREEING tests are racy because clear_inode() can set i_state to
> I_CLEAR between the clear of I_SYNC and the test of I_FREEING.
>
> 2) skip I_WILL_FREE inodes in generic_sync_sb_inodes() to avoid possible
> races with generic_forget_inode()
>
> generic_forget_inode() sets I_WILL_FREE call writeback on its own, so
> generic_sync_sb_inodes() shall not try to step in and create possible races:
>
> generic_forget_inode
> inode->i_state |= I_WILL_FREE;
> spin_unlock(&inode_lock);
> generic_sync_sb_inodes()
> spin_lock(&inode_lock);
> __iget(inode);
> __writeback_single_inode
> // see non zero i_count
> may WARN here ==> WARN_ON(inode->i_state & I_WILL_FREE);
> spin_unlock(&inode_lock);
> may call generic_forget_inode again ==> iput(inode);
>
> The above race and warning didn't turn up because writeback_inodes() holds
> the s_umount lock, so generic_forget_inode() finds MS_ACTIVE and returns
> early. But we are not sure the UBIFS calls and future callers will guarantee
> that. So skip I_WILL_FREE inodes for the sake of safety.
OK, the patch looks fine. Acked-by: Jan Kara <jack@xxxxxxx>
Honza
> CC: Jan Kara <jack@xxxxxxx>
> CC: Eric Sandeen <sandeen@xxxxxxxxxxx>
> Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
> CC: Masayoshi MIZUMA <m.mizuma@xxxxxxxxxxxxxx>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> ---
> fs/fs-writeback.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> --- linux.orig/fs/fs-writeback.c
> +++ linux/fs/fs-writeback.c
> @@ -316,7 +316,7 @@ __sync_single_inode(struct inode *inode,
> spin_lock(&inode_lock);
> WARN_ON(inode->i_state & I_NEW);
> inode->i_state &= ~I_SYNC;
> - if (!(inode->i_state & I_FREEING)) {
> + if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
> if (!(inode->i_state & I_DIRTY) &&
> mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
> /*
> @@ -487,7 +487,7 @@ void generic_sync_sb_inodes(struct super
> break;
> }
>
> - if (inode->i_state & I_NEW) {
> + if (inode->i_state & (I_NEW | I_WILL_FREE)) {
> requeue_io(inode);
> continue;
> }
> @@ -518,7 +518,7 @@ void generic_sync_sb_inodes(struct super
> if (current_is_pdflush() && !writeback_acquire(bdi))
> break;
>
> - BUG_ON(inode->i_state & I_FREEING);
> + BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
> __iget(inode);
> pages_skipped = wbc->pages_skipped;
> __writeback_single_inode(inode, wbc);
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
