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SubjectRe: [f2fs-dev] [PATCH 2/2] f2fs: don't give partially written atomic data from process crash
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On 2017/7/26 9:29, Jaegeuk Kim wrote:
> This patch resolves the below scenario.
>
> == Process 1 == == Process 2 ==
> open(w) open(rw)
> begin
> write(new_#1)
> process_crash
> f_op->flush
> locks_remove_posix
> f_op>release
> read (new_#1)
>
> In order to avoid corrupted database caused by new_#1, we must do roll-back
> at process_crash time. In order to check that, this patch keeps task which
> triggers transaction begin, and does roll-back in f_op->flush before removing
> file locks.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

> ---
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/file.c | 18 ++++++++++++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index a336021b777f..3e48c2ac2f21 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -565,6 +565,7 @@ struct f2fs_inode_info {
> struct list_head dirty_list; /* dirty list for dirs and files */
> struct list_head gdirty_list; /* linked in global dirty list */
> struct list_head inmem_pages; /* inmemory pages managed by f2fs */
> + struct task_struct *inmem_task; /* store inmemory task */
> struct mutex inmem_lock; /* lock for inmemory pages */
> struct extent_tree *extent_tree; /* cached extent_tree entry */
> struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 0f4dbeb61845..cb0a013859e6 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1502,6 +1502,22 @@ static int f2fs_release_file(struct inode *inode, struct file *filp)
> return 0;
> }
>
> +static int f2fs_file_flush(struct file *file, fl_owner_t id)
> +{
> + struct inode *inode = file_inode(file);
> +
> + /*
> + * If the process doing a transaction is crashed, we should do
> + * roll-back. Otherwise, other reader/write can see corrupted database
> + * until all the writers close its file. Since this should be done
> + * before dropping file lock, it needs to do in ->flush.
> + */
> + if (f2fs_is_atomic_file(inode) &&
> + F2FS_I(inode)->inmem_task == current)
> + drop_inmem_pages(inode);
> + return 0;
> +}
> +
> static int f2fs_ioc_getflags(struct file *filp, unsigned long arg)
> {
> struct inode *inode = file_inode(filp);
> @@ -1608,6 +1624,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
> }
>
> inc_stat:
> + F2FS_I(inode)->inmem_task = current;
> stat_inc_atomic_write(inode);
> stat_update_max_atomic_write(inode);
> out:
> @@ -2514,6 +2531,7 @@ const struct file_operations f2fs_file_operations = {
> .open = f2fs_file_open,
> .release = f2fs_release_file,
> .mmap = f2fs_file_mmap,
> + .flush = f2fs_file_flush,
> .fsync = f2fs_sync_file,
> .fallocate = f2fs_fallocate,
> .unlocked_ioctl = f2fs_ioctl,
>

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