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SubjectRe: [Ocfs2-devel] [PATCH 3/3] ocfs2: nowait aio support
Hi Gang,

On 2017/11/27 17:46, Gang He wrote:
> Return EAGAIN if any of the following checks fail for direct I/O:
> Can not get the related locks immediately,
> Blocks are not allocated at the write location, it will trigger
> block allocation and block IO operations.
>
> Signed-off-by: Gang He <ghe@suse.com>
> ---
> fs/ocfs2/dir.c | 2 +-
> fs/ocfs2/dlmglue.c | 20 ++++++++++----
> fs/ocfs2/dlmglue.h | 2 +-
> fs/ocfs2/file.c | 74 +++++++++++++++++++++++++++++++++++++-------------
> fs/ocfs2/mmap.c | 2 +-
> fs/ocfs2/ocfs2_trace.h | 10 ++++---
> 6 files changed, 79 insertions(+), 31 deletions(-)
>
> diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
> index febe631..ea50901 100644
> --- a/fs/ocfs2/dir.c
> +++ b/fs/ocfs2/dir.c
> @@ -1957,7 +1957,7 @@ int ocfs2_readdir(struct file *file, struct dir_context *ctx)
>
> trace_ocfs2_readdir((unsigned long long)OCFS2_I(inode)->ip_blkno);
>
> - error = ocfs2_inode_lock_atime(inode, file->f_path.mnt, &lock_level);
> + error = ocfs2_inode_lock_atime(inode, file->f_path.mnt, &lock_level, 1);
> if (lock_level && error >= 0) {
> /* We release EX lock which used to update atime
> * and get PR lock again to reduce contention
> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
> index 5cfbd04..feb8dbe 100644
> --- a/fs/ocfs2/dlmglue.c
> +++ b/fs/ocfs2/dlmglue.c
> @@ -2516,13 +2516,18 @@ int ocfs2_inode_lock_with_page(struct inode *inode,
>
> int ocfs2_inode_lock_atime(struct inode *inode,
> struct vfsmount *vfsmnt,
> - int *level)
> + int *level, int wait)
> {
> int ret;
>
> - ret = ocfs2_inode_lock(inode, NULL, 0);
> + if (wait)
> + ret = ocfs2_inode_lock(inode, NULL, 0);
> + else
> + ret = ocfs2_try_inode_lock(inode, NULL, 0);
> +
> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> return ret;
> }
>
> @@ -2534,9 +2539,14 @@ int ocfs2_inode_lock_atime(struct inode *inode,
> struct buffer_head *bh = NULL;
>
> ocfs2_inode_unlock(inode, 0);
> - ret = ocfs2_inode_lock(inode, &bh, 1);
> + if (wait)
> + ret = ocfs2_inode_lock(inode, &bh, 1);
> + else
> + ret = ocfs2_try_inode_lock(inode, &bh, 1);
> +
> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> return ret;
> }
> *level = 1;
> diff --git a/fs/ocfs2/dlmglue.h b/fs/ocfs2/dlmglue.h
> index 05910fc..c83dbb5 100644
> --- a/fs/ocfs2/dlmglue.h
> +++ b/fs/ocfs2/dlmglue.h
> @@ -123,7 +123,7 @@ void ocfs2_refcount_lock_res_init(struct ocfs2_lock_res *lockres,
> void ocfs2_open_unlock(struct inode *inode);
> int ocfs2_inode_lock_atime(struct inode *inode,
> struct vfsmount *vfsmnt,
> - int *level);
> + int *level, int wait);
> int ocfs2_inode_lock_full_nested(struct inode *inode,
> struct buffer_head **ret_bh,
> int ex,
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index dc455d4..900f04e 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -140,6 +140,8 @@ static int ocfs2_file_open(struct inode *inode, struct file *file)
> spin_unlock(&oi->ip_lock);
> }
>
> + file->f_mode |= FMODE_NOWAIT;
> +
> leave:
> return status;
> }
> @@ -2132,8 +2134,7 @@ static int ocfs2_prepare_inode_for_refcount(struct inode *inode,
> }
>
> static int ocfs2_prepare_inode_for_write(struct file *file,
> - loff_t pos,
> - size_t count)
> + loff_t pos, size_t count, int wait)
> {
> int ret = 0, meta_level = 0;
> struct dentry *dentry = file->f_path.dentry;
> @@ -2145,10 +2146,14 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
> * if we need to make modifications here.
> */
> for(;;) {
> - ret = ocfs2_inode_lock(inode, NULL, meta_level);
> + if (wait)
> + ret = ocfs2_inode_lock(inode, NULL, meta_level);
> + else
> + ret = ocfs2_try_inode_lock(inode, NULL, meta_level);
> if (ret < 0) {
> meta_level = -1;
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> goto out;
> }
>

We will lock inode again in ocfs2_prepare_inode_for_write()->ocfs2_prepare_inode_for_refcount().
Should we add the check of 'nowait' flags?

> @@ -2199,7 +2204,7 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
>
> out_unlock:
> trace_ocfs2_prepare_inode_for_write(OCFS2_I(inode)->ip_blkno,
> - pos, count);
> + pos, count, wait);
>
> if (meta_level >= 0)
> ocfs2_inode_unlock(inode, meta_level);
> @@ -2211,7 +2216,7 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
> static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> struct iov_iter *from)
> {
> - int direct_io, rw_level;
> + int rw_level;
> ssize_t written = 0;
> ssize_t ret;
> size_t count = iov_iter_count(from);
> @@ -2223,6 +2228,8 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> void *saved_ki_complete = NULL;
> int append_write = ((iocb->ki_pos + count) >=
> i_size_read(inode) ? 1 : 0);
> + int direct_io = iocb->ki_flags & IOCB_DIRECT ? 1 : 0;
> + int nowait = iocb->ki_flags & IOCB_NOWAIT ? 1 : 0;
>
> trace_ocfs2_file_aio_write(inode, file, file->f_path.dentry,
> (unsigned long long)OCFS2_I(inode)->ip_blkno,
> @@ -2230,12 +2237,17 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> file->f_path.dentry->d_name.name,
> (unsigned int)from->nr_segs); /* GRRRRR */
>
> + if (!direct_io && nowait)
> + return -EOPNOTSUPP;
> +
> if (count == 0)
> return 0;
>
> - direct_io = iocb->ki_flags & IOCB_DIRECT ? 1 : 0;
> -
> - inode_lock(inode);
> + if (direct_io && nowait) {
> + if (!inode_trylock(inode))
> + return -EAGAIN;
> + } else
> + inode_lock(inode);
>
> /*
> * Concurrent O_DIRECT writes are allowed with
> @@ -2244,9 +2256,13 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> */
> rw_level = (!direct_io || full_coherency || append_write);
>
> - ret = ocfs2_rw_lock(inode, rw_level);
> + if (direct_io && nowait)
> + ret = ocfs2_try_rw_lock(inode, rw_level);
> + else
> + ret = ocfs2_rw_lock(inode, rw_level);
> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> goto out_mutex;
> }
>
> @@ -2260,9 +2276,13 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> * other nodes to drop their caches. Buffered I/O
> * already does this in write_begin().
> */
> - ret = ocfs2_inode_lock(inode, NULL, 1);
> + if (nowait)
> + ret = ocfs2_try_inode_lock(inode, NULL, 1);
> + else
> + ret = ocfs2_inode_lock(inode, NULL, 1);
> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> goto out;
> }
>
> @@ -2277,9 +2297,17 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> }
> count = ret;
>
> - ret = ocfs2_prepare_inode_for_write(file, iocb->ki_pos, count);
> + if (direct_io && nowait) {
> + if (!ocfs2_overwrite_io(inode, iocb->ki_pos, count, 0)) {
> + ret = -EAGAIN;
> + goto out;
> + }
> + }
> +
> + ret = ocfs2_prepare_inode_for_write(file, iocb->ki_pos, count, !nowait);
> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> goto out;
> }
>
> @@ -2355,6 +2383,7 @@ static ssize_t ocfs2_file_read_iter(struct kiocb *iocb,
> int ret = 0, rw_level = -1, lock_level = 0;
> struct file *filp = iocb->ki_filp;
> struct inode *inode = file_inode(filp);
> + int nowait = iocb->ki_flags & IOCB_NOWAIT ? 1 : 0;
>
> trace_ocfs2_file_aio_read(inode, filp, filp->f_path.dentry,
> (unsigned long long)OCFS2_I(inode)->ip_blkno,
> @@ -2374,9 +2403,14 @@ static ssize_t ocfs2_file_read_iter(struct kiocb *iocb,
> * need locks to protect pending reads from racing with truncate.
> */
> if (iocb->ki_flags & IOCB_DIRECT) {
> - ret = ocfs2_rw_lock(inode, 0);
> + if (nowait)
> + ret = ocfs2_try_rw_lock(inode, 0);
> + else
> + ret = ocfs2_rw_lock(inode, 0);
> +
> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> goto bail;
> }
> rw_level = 0;
> @@ -2393,9 +2427,11 @@ static ssize_t ocfs2_file_read_iter(struct kiocb *iocb,
> * like i_size. This allows the checks down below
> * generic_file_aio_read() a chance of actually working.
> */
> - ret = ocfs2_inode_lock_atime(inode, filp->f_path.mnt, &lock_level);
> + ret = ocfs2_inode_lock_atime(inode, filp->f_path.mnt, &lock_level,
> + !nowait);

Should we judge if the flags is included O_DIRECT?

> if (ret < 0) {
> - mlog_errno(ret);
> + if (ret != -EAGAIN)
> + mlog_errno(ret);
> goto bail;
> }
> ocfs2_inode_unlock(inode, lock_level);
> diff --git a/fs/ocfs2/mmap.c b/fs/ocfs2/mmap.c
> index 098f5c7..fb9a20e 100644
> --- a/fs/ocfs2/mmap.c
> +++ b/fs/ocfs2/mmap.c
> @@ -184,7 +184,7 @@ int ocfs2_mmap(struct file *file, struct vm_area_struct *vma)
> int ret = 0, lock_level = 0;
>
> ret = ocfs2_inode_lock_atime(file_inode(file),
> - file->f_path.mnt, &lock_level);
> + file->f_path.mnt, &lock_level, 1);
> if (ret < 0) {
> mlog_errno(ret);
> goto out;
> diff --git a/fs/ocfs2/ocfs2_trace.h b/fs/ocfs2/ocfs2_trace.h
> index a0b5d00..e2a11aa 100644
> --- a/fs/ocfs2/ocfs2_trace.h
> +++ b/fs/ocfs2/ocfs2_trace.h
> @@ -1449,20 +1449,22 @@
>
> TRACE_EVENT(ocfs2_prepare_inode_for_write,
> TP_PROTO(unsigned long long ino, unsigned long long saved_pos,
> - unsigned long count),
> - TP_ARGS(ino, saved_pos, count),
> + unsigned long count, int wait),
> + TP_ARGS(ino, saved_pos, count, wait),
> TP_STRUCT__entry(
> __field(unsigned long long, ino)
> __field(unsigned long long, saved_pos)
> __field(unsigned long, count)
> + __field(int, wait)
> ),
> TP_fast_assign(
> __entry->ino = ino;
> __entry->saved_pos = saved_pos;
> __entry->count = count;
> + __entry->wait = wait;
> ),
> - TP_printk("%llu %llu %lu", __entry->ino,
> - __entry->saved_pos, __entry->count)
> + TP_printk("%llu %llu %lu %d", __entry->ino,
> + __entry->saved_pos, __entry->count, __entry->wait)
> );
>
> DEFINE_OCFS2_INT_EVENT(generic_file_aio_read_ret);
>

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