On Tuesday, March 12, 2013 at 9:50 PM, Yan, Zheng wrote: > On 03/13/2013 09:24 AM, Greg Farnum wrote: > > On Monday, March 11, 2013 at 5:42 AM, Yan, Zheng wrote: > > > From: "Yan, Zheng" <zheng.z.yan@xxxxxxxxx (mailto:zheng.z.yan@xxxxxxxxx)> > > > > > > Current ceph code tracks directory's completeness in two places. > > > ceph_readdir() checks i_release_count to decide if it can set the > > > I_COMPLETE flag in i_ceph_flags. All other places check the I_COMPLETE > > > flag. This indirection introduces locking complexity. > > > > > > This patch adds a new variable i_complete_count to ceph_inode_info. > > > Set i_release_count's value to it when marking a directory complete. > > > By comparing the two variables, we know if a directory is complete > > > > > > Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx (mailto:zheng.z.yan@xxxxxxxxx)> > > > --- > > > fs/ceph/caps.c | 4 ++-- > > > fs/ceph/dir.c | 25 +++++++++++++------------ > > > fs/ceph/inode.c | 13 +++++++------ > > > fs/ceph/mds_client.c | 10 +++------- > > > fs/ceph/super.h | 41 +++++++++++++++++++---------------------- > > > 5 files changed, 44 insertions(+), 49 deletions(-) > > > > > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c > > > index 76634f4..124e8a1 100644 > > > --- a/fs/ceph/caps.c > > > +++ b/fs/ceph/caps.c > > > @@ -490,7 +490,7 @@ static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap, > > > ci->i_rdcache_gen++; > > > > > > /* > > > - * if we are newly issued FILE_SHARED, clear I_COMPLETE; we > > > + * if we are newly issued FILE_SHARED, mark dir not complete; we > > > * don't know what happened to this directory while we didn't > > > * have the cap. > > > */ > > > @@ -499,7 +499,7 @@ static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap, > > > ci->i_shared_gen++; > > > if (S_ISDIR(ci->vfs_inode.i_mode)) { > > > dout(" marking %p NOT complete\n", &ci->vfs_inode); > > > - ci->i_ceph_flags &= ~CEPH_I_COMPLETE; > > > + __ceph_dir_clear_complete(ci); > > > } > > > } > > > } > > > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c > > > index 76821be..11966c4 100644 > > > --- a/fs/ceph/dir.c > > > +++ b/fs/ceph/dir.c > > > @@ -107,7 +107,7 @@ static unsigned fpos_off(loff_t p) > > > * falling back to a "normal" sync readdir if any dentries in the dir > > > * are dropped. > > > * > > > - * I_COMPLETE tells indicates we have all dentries in the dir. It is > > > + * Complete dir indicates that we have all dentries in the dir. It is > > > * defined IFF we hold CEPH_CAP_FILE_SHARED (which will be revoked by > > > * the MDS if/when the directory is modified). > > > */ > > > @@ -198,8 +198,8 @@ more: > > > filp->f_pos++; > > > > > > /* make sure a dentry wasn't dropped while we didn't have parent lock */ > > > - if (!ceph_i_test(dir, CEPH_I_COMPLETE)) { > > > - dout(" lost I_COMPLETE on %p; falling back to mds\n", dir); > > > + if (!ceph_dir_is_complete(dir)) { > > > + dout(" lost dir complete on %p; falling back to mds\n", dir); > > > err = -EAGAIN; > > > goto out; > > > } > > > @@ -258,7 +258,7 @@ static int ceph_readdir(struct file *filp, void *dirent, filldir_t filldir) > > > if (filp->f_pos == 0) { > > > /* note dir version at start of readdir so we can tell > > > * if any dentries get dropped */ > > > - fi->dir_release_count = ci->i_release_count; > > > + fi->dir_release_count = atomic_read(&ci->i_release_count); > > > > > > dout("readdir off 0 -> '.'\n"); > > > if (filldir(dirent, ".", 1, ceph_make_fpos(0, 0), > > > @@ -284,7 +284,7 @@ static int ceph_readdir(struct file *filp, void *dirent, filldir_t filldir) > > > if ((filp->f_pos == 2 || fi->dentry) && > > > !ceph_test_mount_opt(fsc, NOASYNCREADDIR) && > > > ceph_snap(inode) != CEPH_SNAPDIR && > > > - (ci->i_ceph_flags & CEPH_I_COMPLETE) && > > > + __ceph_dir_is_complete(ci) && > > > __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1)) { > > > spin_unlock(&ci->i_ceph_lock); > > > err = __dcache_readdir(filp, dirent, filldir); > > > @@ -350,7 +350,8 @@ more: > > > > > > if (!req->r_did_prepopulate) { > > > dout("readdir !did_prepopulate"); > > > - fi->dir_release_count--; /* preclude I_COMPLETE */ > > > + /* preclude from marking dir complete */ > > > + fi->dir_release_count--; > > > } > > > > > > /* note next offset and last dentry name */ > > > @@ -428,9 +429,9 @@ more: > > > * the complete dir contents in our cache. > > > */ > > > spin_lock(&ci->i_ceph_lock); > > > - if (ci->i_release_count == fi->dir_release_count) { > > > + if (atomic_read(&ci->i_release_count) == fi->dir_release_count) { > > > dout(" marking %p complete\n", inode); > > > - ci->i_ceph_flags |= CEPH_I_COMPLETE; > > > + __ceph_dir_set_complete(ci, fi->dir_release_count); > > > ci->i_max_offset = filp->f_pos; > > > } > > > spin_unlock(&ci->i_ceph_lock); > > > @@ -605,7 +606,7 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry, > > > fsc->mount_options->snapdir_name, > > > dentry->d_name.len) && > > > !is_root_ceph_dentry(dir, dentry) && > > > - (ci->i_ceph_flags & CEPH_I_COMPLETE) && > > > + __ceph_dir_is_complete(ci) && > > > (__ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1))) { > > > spin_unlock(&ci->i_ceph_lock); > > > dout(" dir %p complete, -ENOENT\n", dir); > > > @@ -909,7 +910,7 @@ static int ceph_rename(struct inode *old_dir, struct dentry *old_dentry, > > > */ > > > > > > /* d_move screws up d_subdirs order */ > > > - ceph_i_clear(new_dir, CEPH_I_COMPLETE); > > > + ceph_dir_clear_complete(new_dir); > > > > > > d_move(old_dentry, new_dentry); > > > > > > @@ -1079,7 +1080,7 @@ static void ceph_d_prune(struct dentry *dentry) > > > if (IS_ROOT(dentry)) > > > return; > > > > > > - /* if we are not hashed, we don't affect I_COMPLETE */ > > > + /* if we are not hashed, we don't affect dir's completeness */ > > > if (d_unhashed(dentry)) > > > return; > > > > > > @@ -1087,7 +1088,7 @@ static void ceph_d_prune(struct dentry *dentry) > > > * we hold d_lock, so d_parent is stable, and d_fsdata is never > > > * cleared until d_release > > > */ > > > - ceph_i_clear(dentry->d_parent->d_inode, CEPH_I_COMPLETE); > > > + ceph_dir_clear_complete(dentry->d_parent->d_inode); > > > } > > > > > > /* > > > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c > > > index 2b3fee7..d8db2df 100644 > > > --- a/fs/ceph/inode.c > > > +++ b/fs/ceph/inode.c > > > @@ -302,7 +302,8 @@ struct inode *ceph_alloc_inode(struct super_block *sb) > > > ci->i_version = 0; > > > ci->i_time_warp_seq = 0; > > > ci->i_ceph_flags = 0; > > > - ci->i_release_count = 0; > > > + ci->i_complete_count = 0; > > > + atomic_set(&ci->i_release_count, 1); > > > ci->i_symlink = NULL; > > > > > > memset(&ci->i_dir_layout, 0, sizeof(ci->i_dir_layout)); > > > @@ -720,9 +721,9 @@ static int fill_inode(struct inode *inode, > > > ceph_snap(inode) == CEPH_NOSNAP && > > > (le32_to_cpu(info->cap.caps) & CEPH_CAP_FILE_SHARED) && > > > (issued & CEPH_CAP_FILE_EXCL) == 0 && > > > - (ci->i_ceph_flags & CEPH_I_COMPLETE) == 0) { > > > + !__ceph_dir_is_complete(ci)) { > > > dout(" marking %p complete (empty)\n", inode); > > > - ci->i_ceph_flags |= CEPH_I_COMPLETE; > > > + __ceph_dir_set_complete(ci, atomic_read(&ci->i_release_count)); > > > ci->i_max_offset = 2; > > > } > > > no_change: > > > @@ -856,7 +857,7 @@ static void ceph_set_dentry_offset(struct dentry *dn) > > > di = ceph_dentry(dn); > > > > > > spin_lock(&ci->i_ceph_lock); > > > - if ((ceph_inode(inode)->i_ceph_flags & CEPH_I_COMPLETE) == 0) { > > > + if (!__ceph_dir_is_complete(ci)) { > > > spin_unlock(&ci->i_ceph_lock); > > > return; > > > } > > > @@ -1060,8 +1061,8 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req, > > > /* > > > * d_move() puts the renamed dentry at the end of > > > * d_subdirs. We need to assign it an appropriate > > > - * directory offset so we can behave when holding > > > - * I_COMPLETE. > > > + * directory offset so we can behave when dir is > > > + * complete. > > > */ > > > ceph_set_dentry_offset(req->r_old_dentry); > > > dout("dn %p gets new offset %lld\n", req->r_old_dentry, > > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c > > > index ab899c8..edf90a5 100644 > > > --- a/fs/ceph/mds_client.c > > > +++ b/fs/ceph/mds_client.c > > > @@ -2030,20 +2030,16 @@ out: > > > } > > > > > > /* > > > - * Invalidate dir I_COMPLETE, dentry lease state on an aborted MDS > > > + * Invalidate dir's completeness, dentry lease state on an aborted MDS > > > * namespace request. > > > */ > > > void ceph_invalidate_dir_request(struct ceph_mds_request *req) > > > { > > > struct inode *inode = req->r_locked_dir; > > > - struct ceph_inode_info *ci = ceph_inode(inode); > > > > > > - dout("invalidate_dir_request %p (I_COMPLETE, lease(s))\n", inode); > > > - spin_lock(&ci->i_ceph_lock); > > > - ci->i_ceph_flags &= ~CEPH_I_COMPLETE; > > > - ci->i_release_count++; > > > - spin_unlock(&ci->i_ceph_lock); > > > + dout("invalidate_dir_request %p (complete, lease(s))\n", inode); > > > > > > + ceph_dir_clear_complete(inode); > > > if (req->r_dentry) > > > ceph_invalidate_dentry_lease(req->r_dentry); > > > if (req->r_old_dentry) > > > diff --git a/fs/ceph/super.h b/fs/ceph/super.h > > > index e5f1875..dde77ac 100644 > > > --- a/fs/ceph/super.h > > > +++ b/fs/ceph/super.h > > > @@ -244,7 +244,8 @@ struct ceph_inode_info { > > > u32 i_time_warp_seq; > > > > > > unsigned i_ceph_flags; > > > - unsigned long i_release_count; > > > + int i_complete_count; > > > + atomic_t i_release_count; > > > > > > > > What makes it safe to treat i_complete_count as an int instead of an atomic? As far as I can tell it's not consistently used under any locks, but maybe I'm missing something that the VFS is giving me. :/ > > -Greg > > > > The code only assigns value to i_complete_count, the instruction is inherent atomic. > That doesn't make sense to me — we read from it every time we check __ceph_dir_is_complete()? Although a 32-bit assignment is generally thread-safe you can't count on it (I believe there are some not-real-far-outside-the-mainstream arches where that's not the case), and in fact it was recently pointed out to me that doing so with a variable of any length is technically undefined behavior: http://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong Anyway, if that's what you meant I think it's better to use the atomics and make the code obviously correct with easy-to-follow semantics, especially given the number of times and people that have gotten it wrong around this directory completeness already! -Greg -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
