Maintain i_dio_count for all filesystems, not just those using DIO_LOCKING. This these filesystems to also protect truncate against direct I/O requests by using common code. Right now the only non-DIO_LOCKING filesystem that appears to do so is XFS, which uses an opencoded variant of the i_dio_count scheme.
Behaviour doesn't change for filesystems never calling inode_dio_wait, which are all that never use DIO_LOCKING. For ext4 behaviour changes with the dioread_nonlock option, which previous was missing any protection between truncate and direct I/O reads. For ocfs2 that handcrafted i_dio_count manipulations are replaced with the common code noew available. As a result inode_dio_wake can now be made static in direct-io.c. Signed-off-by: Christoph Hellwig <[email protected]> Index: linux-2.6/fs/direct-io.c =================================================================== --- linux-2.6.orig/fs/direct-io.c 2011-06-20 14:55:34.602490284 +0200 +++ linux-2.6/fs/direct-io.c 2011-06-20 14:57:24.575818051 +0200 @@ -149,12 +149,11 @@ void inode_dio_wait(struct inode *inode) } EXPORT_SYMBOL_GPL(inode_dio_wait); -void inode_dio_wake(struct inode *inode) +static inline void inode_dio_wake(struct inode *inode) { if (atomic_dec_and_test(&inode->i_dio_count)) wake_up_bit(&inode->i_state, __I_DIO_WAKEUP); } -EXPORT_SYMBOL_GPL(inode_dio_wake); /* * How many pages are in the queue? @@ -274,8 +273,7 @@ static ssize_t dio_complete(struct dio * aio_complete(dio->iocb, ret, 0); } - if (dio->flags & DIO_LOCKING) - inode_dio_wake(dio->inode); + inode_dio_wake(dio->inode); return ret; } @@ -1162,14 +1160,16 @@ direct_io_worker(int rw, struct kiocb *i * For writes this function is called under i_mutex and returns with * i_mutex held, for reads, i_mutex is not held on entry, but it is * taken and dropped again before returning. - * The i_dio_count counter keeps track of the number of outstanding - * direct I/O requests, and truncate waits for it to reach zero. - * New references to i_dio_count must only be grabbed with i_mutex - * held. - * * - if the flags value does NOT contain DIO_LOCKING we don't use any * internal locking but rather rely on the filesystem to synchronize * direct I/O reads/writes versus each other and truncate. + * + * To help with locking against truncate we incremented the i_dio_count + * counter before starting direct I/O, and decrement it once we are done. + * Truncate can wait for it to reach zero to provide exclusion. It is + * expected that filesystem provide exclusion between new direct I/O + * and truncates. For DIO_LOCKING filesystems this is done by i_mutex, + * but other filesystems need to take care of this on their own. */ ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, @@ -1247,14 +1247,14 @@ __blockdev_direct_IO(int rw, struct kioc goto out; } } - - /* - * Will be decremented at I/O completion time. - */ - atomic_inc(&inode->i_dio_count); } /* + * Will be decremented at I/O completion time. + */ + atomic_inc(&inode->i_dio_count); + + /* * For file extending writes updating i_size before data * writeouts complete can expose uninitialized blocks. So * even for AIO, we need to wait for i/o to complete before Index: linux-2.6/fs/ocfs2/aops.c =================================================================== --- linux-2.6.orig/fs/ocfs2/aops.c 2011-06-20 14:55:34.629156951 +0200 +++ linux-2.6/fs/ocfs2/aops.c 2011-06-20 14:56:59.259152666 +0200 @@ -567,10 +567,8 @@ static void ocfs2_dio_end_io(struct kioc /* this io's submitter should not have unlocked this before we could */ BUG_ON(!ocfs2_iocb_is_rw_locked(iocb)); - if (ocfs2_iocb_is_sem_locked(iocb)) { - inode_dio_wake(inode); + if (ocfs2_iocb_is_sem_locked(iocb)) ocfs2_iocb_clear_sem_locked(iocb); - } ocfs2_iocb_clear_rw_locked(iocb); Index: linux-2.6/fs/ocfs2/file.c =================================================================== --- linux-2.6.orig/fs/ocfs2/file.c 2011-06-20 14:56:55.375819530 +0200 +++ linux-2.6/fs/ocfs2/file.c 2011-06-20 14:56:59.262485999 +0200 @@ -2240,7 +2240,6 @@ static ssize_t ocfs2_file_aio_write(stru relock: /* to match setattr's i_mutex -> rw_lock ordering */ if (direct_io) { - atomic_inc(&inode->i_dio_count); have_alloc_sem = 1; /* communicate with ocfs2_dio_end_io */ ocfs2_iocb_set_sem_locked(iocb); @@ -2292,7 +2291,6 @@ relock: */ if (direct_io && !can_do_direct) { ocfs2_rw_unlock(inode, rw_level); - inode_dio_wake(inode); have_alloc_sem = 0; rw_level = -1; @@ -2379,10 +2377,8 @@ out: ocfs2_rw_unlock(inode, rw_level); out_sems: - if (have_alloc_sem) { - inode_dio_wake(inode); + if (have_alloc_sem) ocfs2_iocb_clear_sem_locked(iocb); - } mutex_unlock(&inode->i_mutex); @@ -2533,7 +2529,6 @@ static ssize_t ocfs2_file_aio_read(struc */ if (filp->f_flags & O_DIRECT) { have_alloc_sem = 1; - atomic_inc(&inode->i_dio_count); ocfs2_iocb_set_sem_locked(iocb); ret = ocfs2_rw_lock(inode, 0); @@ -2575,10 +2570,9 @@ static ssize_t ocfs2_file_aio_read(struc } bail: - if (have_alloc_sem) { - inode_dio_wake(inode); + if (have_alloc_sem) ocfs2_iocb_clear_sem_locked(iocb); - } + if (rw_level != -1) ocfs2_rw_unlock(inode, rw_level); Index: linux-2.6/include/linux/fs.h =================================================================== --- linux-2.6.orig/include/linux/fs.h 2011-06-20 14:57:08.582485528 +0200 +++ linux-2.6/include/linux/fs.h 2011-06-20 14:57:10.099152117 +0200 @@ -2373,7 +2373,6 @@ enum { void dio_end_io(struct bio *bio, int error); void inode_dio_wait(struct inode *inode); -void inode_dio_wake(struct inode *inode); ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, struct block_device *bdev, const struct iovec *iov, loff_t offset, -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
