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SubjectRe: [Ocfs2-devel] [PATCH 3/3] ocfs2: nowait aio support
Hello Alex,


>>>
> 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?
I think ocfs2_overwrite_io() function can make sure ocfs2_prepare_inode_for_refcount() is passed,
but it looks there is a race condition between ocfs2_overwrite_io() and ocfs2_prepare_inode_for_write() since inode lock is released.
I think I will move ocfs2_overwrite_io() function invoking in ocfs2_prepare_inode_for_write() to avoid this race.

Thanks
Gang


>
>> @@ -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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