On Thu, 2020-02-20 at 21:33 +0800, Yan, Zheng wrote:
> On Thu, Feb 20, 2020 at 9:01 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > On Thu, 2020-02-20 at 11:32 +0800, Yan, Zheng wrote:
> > > On Wed, Feb 19, 2020 at 9:27 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > > > When we issue an async create, we must ensure that any later on-the-wire
> > > > requests involving it wait for the create reply.
> > > >
> > > > Expand i_ceph_flags to be an unsigned long, and add a new bit that
> > > > MDS requests can wait on. If the bit is set in the inode when sending
> > > > caps, then don't send it and just return that it has been delayed.
> > > >
> > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > > ---
> > > > fs/ceph/caps.c | 13 ++++++++++++-
> > > > fs/ceph/dir.c | 2 +-
> > > > fs/ceph/mds_client.c | 20 +++++++++++++++++++-
> > > > fs/ceph/mds_client.h | 7 +++++++
> > > > fs/ceph/super.h | 4 +++-
> > > > 5 files changed, 42 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> > > > index d05717397c2a..85e13aa359d2 100644
> > > > --- a/fs/ceph/caps.c
> > > > +++ b/fs/ceph/caps.c
> > > > @@ -511,7 +511,7 @@ static void __cap_delay_requeue(struct ceph_mds_client *mdsc,
> > > > struct ceph_inode_info *ci,
> > > > bool set_timeout)
> > > > {
> > > > - dout("__cap_delay_requeue %p flags %d at %lu\n", &ci->vfs_inode,
> > > > + dout("__cap_delay_requeue %p flags 0x%lx at %lu\n", &ci->vfs_inode,
> > > > ci->i_ceph_flags, ci->i_hold_caps_max);
> > > > if (!mdsc->stopping) {
> > > > spin_lock(&mdsc->cap_delay_lock);
> > > > @@ -1294,6 +1294,13 @@ static int __send_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap,
> > > > int delayed = 0;
> > > > int ret;
> > > >
> > > > + /* Don't send anything if it's still being created. Return delayed */
> > > > + if (ci->i_ceph_flags & CEPH_I_ASYNC_CREATE) {
> > > > + spin_unlock(&ci->i_ceph_lock);
> > > > + dout("%s async create in flight for %p\n", __func__, inode);
> > > > + return 1;
> > > > + }
> > > > +
> > >
> > > Maybe it's better to check this in ceph_check_caps(). Other callers
> > > of __send_cap() shouldn't encounter async creating inode
> > >
> >
> > I've been looking, but what actually guarantees that?
> >
> > Only ceph_check_caps calls it for UPDATE, but the other two callers call
> > it for FLUSH. I don't see what prevents the kernel from (e.g.) calling
> > write_inode before the create reply comes in, particularly if we just
> > create and then close the file.
> >
>
> I missed write_inode case. but make __send_cap() skip sending message
> can cause problem. For example, if we skip a message that flush dirty
> caps. call ceph_check_caps() again may not re-do the flush.
>
Ugh. Ok, so I guess we'll need to fix that first. I assume that making
sure the flush is redone after being delayed is the right thing to do
here?
> > As a side note, I still struggle with the fact thatthere seems to be no
> > coherent overall description of the cap protocol. What distinguishes a
> > FLUSH from an UPDATE, for instance? The MDS code and comments seem to
> > treat them somewhat interchangeably.
> >
>
> UPDATE is super set of FLUSH, UPDATE can always replace FLUSH.
>
I'll toss this note onto my jumble of notes, for my (eventual) planned
document that describes the cap protocol.
> > > > held = cap->issued | cap->implemented;
> > > > revoking = cap->implemented & ~cap->issued;
> > > > retain &= ~revoking;
> > > > @@ -2250,6 +2257,10 @@ int ceph_fsync(struct file *file, loff_t start, loff_t end, int datasync)
> > > > if (datasync)
> > > > goto out;
> > > >
> > > > + ret = ceph_wait_on_async_create(inode);
> > > > + if (ret)
> > > > + goto out;
> > > > +
> > > > dirty = try_flush_caps(inode, &flush_tid);
> > > > dout("fsync dirty caps are %s\n", ceph_cap_string(dirty));
> > > >
> > > > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> > > > index a87274935a09..5b83bda57056 100644
> > > > --- a/fs/ceph/dir.c
> > > > +++ b/fs/ceph/dir.c
> > > > @@ -752,7 +752,7 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
> > > > struct ceph_dentry_info *di = ceph_dentry(dentry);
> > > >
> > > > spin_lock(&ci->i_ceph_lock);
> > > > - dout(" dir %p flags are %d\n", dir, ci->i_ceph_flags);
> > > > + dout(" dir %p flags are 0x%lx\n", dir, ci->i_ceph_flags);
> > > > if (strncmp(dentry->d_name.name,
> > > > fsc->mount_options->snapdir_name,
> > > > dentry->d_name.len) &&
> > > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > > > index 94d18e643a3d..38eb9dd5062b 100644
> > > > --- a/fs/ceph/mds_client.c
> > > > +++ b/fs/ceph/mds_client.c
> > > > @@ -2730,7 +2730,7 @@ static void kick_requests(struct ceph_mds_client *mdsc, int mds)
> > > > int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
> > > > struct ceph_mds_request *req)
> > > > {
> > > > - int err;
> > > > + int err = 0;
> > > >
> > > > /* take CAP_PIN refs for r_inode, r_parent, r_old_dentry */
> > > > if (req->r_inode)
> > > > @@ -2743,6 +2743,24 @@ int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
> > > > ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
> > > > CEPH_CAP_PIN);
> > > >
> > > > + if (req->r_inode) {
> > > > + err = ceph_wait_on_async_create(req->r_inode);
> > > > + if (err) {
> > > > + dout("%s: wait for async create returned: %d\n",
> > > > + __func__, err);
> > > > + return err;
> > > > + }
> > > > + }
> > > > +
> > > > + if (!err && req->r_old_inode) {
> > > > + err = ceph_wait_on_async_create(req->r_old_inode);
> > > > + if (err) {
> > > > + dout("%s: wait for async create returned: %d\n",
> > > > + __func__, err);
> > > > + return err;
> > > > + }
> > > > + }
> > > > +
> > > > dout("submit_request on %p for inode %p\n", req, dir);
> > > > mutex_lock(&mdsc->mutex);
> > > > __register_request(mdsc, req, dir);
> > > > diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
> > > > index 95ac00e59e66..8043f2b439b1 100644
> > > > --- a/fs/ceph/mds_client.h
> > > > +++ b/fs/ceph/mds_client.h
> > > > @@ -538,4 +538,11 @@ extern void ceph_mdsc_open_export_target_sessions(struct ceph_mds_client *mdsc,
> > > > extern int ceph_trim_caps(struct ceph_mds_client *mdsc,
> > > > struct ceph_mds_session *session,
> > > > int max_caps);
> > > > +static inline int ceph_wait_on_async_create(struct inode *inode)
> > > > +{
> > > > + struct ceph_inode_info *ci = ceph_inode(inode);
> > > > +
> > > > + return wait_on_bit(&ci->i_ceph_flags, CEPH_ASYNC_CREATE_BIT,
> > > > + TASK_INTERRUPTIBLE);
> > > > +}
> > > > #endif
> > > > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > > > index 3430d7ffe8f7..bfb03adb4a08 100644
> > > > --- a/fs/ceph/super.h
> > > > +++ b/fs/ceph/super.h
> > > > @@ -316,7 +316,7 @@ struct ceph_inode_info {
> > > > u64 i_inline_version;
> > > > u32 i_time_warp_seq;
> > > >
> > > > - unsigned i_ceph_flags;
> > > > + unsigned long i_ceph_flags;
> > > > atomic64_t i_release_count;
> > > > atomic64_t i_ordered_count;
> > > > atomic64_t i_complete_seq[2];
> > > > @@ -524,6 +524,8 @@ static inline struct inode *ceph_find_inode(struct super_block *sb,
> > > > #define CEPH_I_ERROR_WRITE (1 << 10) /* have seen write errors */
> > > > #define CEPH_I_ERROR_FILELOCK (1 << 11) /* have seen file lock errors */
> > > > #define CEPH_I_ODIRECT (1 << 12) /* inode in direct I/O mode */
> > > > +#define CEPH_ASYNC_CREATE_BIT (13) /* async create in flight for this */
> > > > +#define CEPH_I_ASYNC_CREATE (1 << CEPH_ASYNC_CREATE_BIT)
> > > >
> > > > /*
> > > > * Masks of ceph inode work.
> > > > --
> > > > 2.24.1
> > > >
> >
> > --
> > Jeff Layton <jlayton@xxxxxxxxxx>
> >
--
Jeff Layton <jlayton@xxxxxxxxxx>
