28 марта 2012 г. 13:54 пользователь Pavel Shilovsky
<piastry@xxxxxxxxxxx> написал:
> We can deadlock if we have a write oplock and two processes
> use the same file handle. In this case the first process can't
> unlock its lock if another process blocked on the lock in the
> same time.
>
> Fix this by removing lock_mutex protection from waiting on a
> blocked lock and protect only posix_lock_file call.
>
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
> ---
> fs/cifs/file.c | 16 ++++++++++++++--
> fs/locks.c | 3 ++-
> include/linux/fs.h | 5 +++++
> 3 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 460d87b..89e4feb 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -840,8 +840,20 @@ cifs_posix_lock_set(struct file *file, struct file_lock *flock)
> mutex_unlock(&cinode->lock_mutex);
> return rc;
> }
> - rc = posix_lock_file_wait(file, flock);
> - mutex_unlock(&cinode->lock_mutex);
> +
> + while (true) {
> + rc = posix_lock_file(file, flock, NULL);
> + mutex_unlock(&cinode->lock_mutex);
> + if (rc != FILE_LOCK_DEFERRED)
> + break;
> + rc = wait_event_interruptible(flock->fl_wait, !flock->fl_next);
> + if (rc) {
> + locks_delete_block(flock);
> + break;
> + }
> + mutex_lock(&cinode->lock_mutex);
> + }
We need to check if we can cache brlocks after
wait_event_interruptible ends (similar to the code we have for
mandatory locking case) - will respin this.
> +
> return rc;
> }
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 637694b..0d68f1f 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -510,12 +510,13 @@ static void __locks_delete_block(struct file_lock *waiter)
>
> /*
> */
> -static void locks_delete_block(struct file_lock *waiter)
> +void locks_delete_block(struct file_lock *waiter)
> {
> lock_flocks();
> __locks_delete_block(waiter);
> unlock_flocks();
> }
> +EXPORT_SYMBOL(locks_delete_block);
>
> /* Insert waiter into blocker's block list.
> * We use a circular list so that processes can be easily woken up in
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index fa63f1b..d8fd8df 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1211,6 +1211,7 @@ extern int vfs_setlease(struct file *, long, struct file_lock **);
> extern int lease_modify(struct file_lock **, int);
> extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
> extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
> +extern void locks_delete_block(struct file_lock *waiter);
> extern void lock_flocks(void);
> extern void unlock_flocks(void);
> #else /* !CONFIG_FILE_LOCKING */
> @@ -1355,6 +1356,10 @@ static inline int lock_may_write(struct inode *inode, loff_t start,
> return 1;
> }
>
> +static inline void locks_delete_block(struct file_lock *waiter)
> +{
> +}
> +
> static inline void lock_flocks(void)
> {
> }
> --
> 1.7.1
>
--
Best regards,
Pavel Shilovsky.
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