X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=blobdiff_plain;f=lustre%2Fosp%2Fosp_precreate.c;h=e42a7f03a0b9ccbecc7e6de313512a40fb6bd114;hp=7c28e1a44dc6f207343ea148a485518dc21bd553;hb=9e15e5077311150712f900fba80879cbf20d4ffb;hpb=4ea13c63f3d919282b12c64d0c014bfe9a67a5e6 diff --git a/lustre/osp/osp_precreate.c b/lustre/osp/osp_precreate.c index 7c28e1a..e42a7f0 100644 --- a/lustre/osp/osp_precreate.c +++ b/lustre/osp/osp_precreate.c @@ -57,7 +57,15 @@ */ /* - * statfs + ** + * Check whether statfs data is expired + * + * OSP device caches statfs data for the target, the function checks + * whether the data is expired or not. + * + * \param[in] d OSP device + * + * \retval 0 - not expired, 1 - expired */ static inline int osp_statfs_need_update(struct osp_device *d) { @@ -90,6 +98,22 @@ static void osp_statfs_timer_cb(unsigned long _d) wake_up(&d->opd_pre_waitq); } +/** + * RPC interpret callback for OST_STATFS RPC + * + * An interpretation callback called by ptlrpc for OST_STATFS RPC when it is + * replied by the target. It's used to maintain statfs cache for the target. + * The function fills data from the reply if succesfull and schedules another + * update. + * + * \param[in] env LU environment provided by the caller + * \param[in] req RPC replied + * \param[in] aa callback data + * \param[in] rc RPC result + * + * \retval 0 on success + * \retval negative negated errno on error + */ static int osp_statfs_interpret(const struct lu_env *env, struct ptlrpc_request *req, union ptlrpc_async_args *aa, int rc) @@ -134,6 +158,16 @@ out: RETURN(rc); } +/** + * Send OST_STATFS RPC + * + * Sends OST_STATFS RPC to refresh cached statfs data for the target. + * Also disables scheduled updates as times OSP may need to refresh + * statfs data before expiration. The function doesn't block, instead + * an interpretation callback osp_statfs_interpret() is used. + * + * \param[in] d OSP device + */ static int osp_statfs_update(struct osp_device *d) { struct ptlrpc_request *req; @@ -177,11 +211,18 @@ static int osp_statfs_update(struct osp_device *d) RETURN(0); } -/* - * XXX: there might be a case where removed object(s) do not add free - * space (empty object). if the number of such deletions is high, then - * we can start to update statfs too often - a rpc storm - * TODO: some throttling is needed +/** + * Schedule an immediate update for statfs data + * + * If cached statfs data claim no free space, but OSP has got a request to + * destroy an object (so release some space probably), then we may need to + * refresh cached statfs data sooner then planned. The function checks there + * is no statfs update going and schedules immediate update if so. + * XXX: there might be a case where removed object(s) do not add free space (empty + * object). If the number of such deletions is high, then we can start to update + * statfs too often causing a RPC storm. some throttling is needed... + * + * \param[in] d OSP device where statfs data needs to be refreshed */ void osp_statfs_need_now(struct osp_device *d) { @@ -197,6 +238,16 @@ void osp_statfs_need_now(struct osp_device *d) } } +/** + * Return number of precreated objects + * + * A simple helper to calculate the number of precreated objects on the device. + * + * \param[in] env LU environment provided by the caller + * \param[in] osp OSP device + * + * \retval the number of the precreated objects + */ static inline int osp_objs_precreated(const struct lu_env *env, struct osp_device *osp) { @@ -204,6 +255,20 @@ static inline int osp_objs_precreated(const struct lu_env *env, &osp->opd_pre_used_fid); } +/** + * Check pool of precreated objects is nearly empty + * + * We should not wait till the pool of the precreated objects is exhausted, + * because then there will be a long period of OSP being unavailable for the + * new creations due to lenghty precreate RPC. Instead we ask for another + * precreation ahead and hopefully have it ready before the current pool is + * empty. Notice this function relies on an external locking. + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 - current pool is good enough, 1 - time to precreate + */ static inline int osp_precreate_near_empty_nolock(const struct lu_env *env, struct osp_device *d) { @@ -215,6 +280,17 @@ static inline int osp_precreate_near_empty_nolock(const struct lu_env *env, (d->opd_pre_status == 0)); } +/** + * Check pool of precreated objects + * + * This is protected version of osp_precreate_near_empty_nolock(), check that + * for the details. + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 - current pool is good enough, 1 - time to precreate + */ static inline int osp_precreate_near_empty(const struct lu_env *env, struct osp_device *d) { @@ -227,6 +303,18 @@ static inline int osp_precreate_near_empty(const struct lu_env *env, return rc; } +/** + * Check given sequence is empty + * + * Returns a binary result whether the given sequence has some IDs left + * or not. Find the details in osp_fid_end_seq(). This is a lock protected + * version of that function. + * + * \param[in] env LU environment provided by the caller + * \param[in] osp OSP device + * + * \retval 0 - current sequence has no IDs, 1 - otherwise + */ static inline int osp_create_end_seq(const struct lu_env *env, struct osp_device *osp) { @@ -240,7 +328,19 @@ static inline int osp_create_end_seq(const struct lu_env *env, } /** - * Write fid into last_oid/last_seq file. + * Write FID into into last_oid/last_seq file + * + * The function stores the sequence and the in-sequence id into two dedicated + * files. The sync argument can be used to request synchronous commit, so the + * function won't return until the updates are committed. + * + * \param[in] env LU environment provided by the caller + * \param[in] osp OSP device + * \param[in] fid fid where sequence/id is taken + * \param[in] sync update mode: 0 - asynchronously, 1 - synchronously + * + * \retval 0 on success + * \retval negative negated errno on error **/ int osp_write_last_oid_seq_files(struct lu_env *env, struct osp_device *osp, struct lu_fid *fid, int sync) @@ -303,6 +403,25 @@ out: RETURN(rc); } +/** + * Switch to another sequence + * + * When a current sequence has no available IDs left, OSP has to switch to + * another new sequence. OSP requests it using the regular FLDB protocol + * and stores synchronously before that is used in precreated. This is needed + * to basically have the sequences referenced (not orphaned), otherwise it's + * possible that OST has some objects precreated and the clients have data + * written to it, but after MDT failover nobody refers those objects and OSP + * has no idea that the sequence need cleanup to be done. + * While this is very expensive operation, it's supposed to happen very very + * infrequently because sequence has 2^32 or 2^48 objects (depending on type) + * + * \param[in] env LU environment provided by the caller + * \param[in] osp OSP device + * + * \retval 0 on success + * \retval negative negated errno on error + */ int osp_precreate_rollover_new_seq(struct lu_env *env, struct osp_device *osp) { struct lu_fid *fid = &osp_env_info(env)->osi_fid; @@ -345,11 +464,23 @@ int osp_precreate_rollover_new_seq(struct lu_env *env, struct osp_device *osp) } /** - * alloc fids for precreation. - * rc = 0 Success, @grow is the count of real allocation. - * rc = 1 Current seq is used up. - * rc < 0 Other error. - **/ + * Find IDs available in current sequence + * + * The function calculates the highest possible ID and the number of IDs + * available in the current sequence OSP is using. The number is limited + * artifically by the caller (grow param) and the number of IDs available + * in the sequence by nature. The function doesn't require an external + * locking. + * + * \param[in] env LU environment provided by the caller + * \param[in] osp OSP device + * \param[in] fid FID the caller wants to start with + * \param[in] grow how many the caller wants + * \param[out] fid the highest calculated FID + * \param[out] grow the number of available IDs calculated + * + * \retval 0 on success, 1 - the sequence is empty + */ static int osp_precreate_fids(const struct lu_env *env, struct osp_device *osp, struct lu_fid *fid, int *grow) { @@ -390,6 +521,21 @@ static int osp_precreate_fids(const struct lu_env *env, struct osp_device *osp, return *grow > 0 ? 0 : 1; } +/** + * Prepare and send precreate RPC + * + * The function finds how many objects should be precreated. Then allocates, + * prepares and schedules precreate RPC synchronously. Upon reply the function + * wake ups the threads waiting for the new objects on this target. If the + * target wasn't able to create all the objects requested, then the next + * precreate will be asking less objects (i.e. slow precreate down). + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 on success + * \retval negative negated errno on error + **/ static int osp_precreate_send(const struct lu_env *env, struct osp_device *d) { struct osp_thread_info *oti = osp_env_info(env); @@ -513,6 +659,20 @@ out_req: RETURN(rc); } +/** + * Get last precreated object from target (OST) + * + * Sends synchronous RPC to the target (OST) to learn the last precreated + * object. This later is used to remove all unused objects (cleanup orphan + * procedure). Also, the next object after one we got will be used as a + * starting point for the new precreates. + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 on success + * \retval negative negated errno on error + **/ static int osp_get_lastfid_from_ost(const struct lu_env *env, struct osp_device *d) { @@ -585,8 +745,21 @@ out: } /** - * asks OST to clean precreate orphans - * and gets next id for new objects + * Cleanup orphans on OST + * + * This function is called in a contex of a dedicated thread handling + * all the precreation suff. The function waits till local recovery + * is complete, then identify all the unreferenced objects (orphans) + * using the highest ID referenced by a local and the highest object + * precreated by the target. The found range is a subject to removal + * using specially flagged RPC. During this process OSP is marked + * unavailable for new objects. + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 on success + * \retval negative negated errno on error */ static int osp_precreate_cleanup_orphans(struct lu_env *env, struct osp_device *d) @@ -737,13 +910,36 @@ out: RETURN(rc); } -/* +/** + * Update precreate status using statfs data + * + * The function decides whether this OSP should be used for new objects. + * IOW, whether this OST is used up or has some free space. Cached statfs + * data is used to make this decision. If the latest result of statfs + * request (rc argument) is not success, then just mark OSP unavailable + * right away. + + * Add a bit of hysteresis so this flag isn't continually flapping, + * and ensure that new files don't get extremely fragmented due to + * only a small amount of available space in the filesystem. + * We want to set the NOSPC flag when there is less than ~0.1% free + * and clear it when there is at least ~0.2% free space, so: + * avail < ~0.1% max max = avail + used + * 1025 * avail < avail + used used = blocks - free + * 1024 * avail < used + * 1024 * avail < blocks - free + * avail < ((blocks - free) >> 10) + * + * On very large disk, say 16TB 0.1% will be 16 GB. We don't want to + * lose that amount of space so in those cases we report no space left + * if their is less than 1 GB left. * the function updates current precreation status used: functional or not * - * rc is a last code from the transport, rc == 0 meaning transport works - * well and users of lod can use objects from this OSP + * \param[in] d OSP device + * \param[in] rc new precreate status for device \a d * - * the status depends on current usage of OST + * \retval 0 on success + * \retval negative negated errno on error */ void osp_pre_update_status(struct osp_device *d, int rc) { @@ -755,20 +951,6 @@ void osp_pre_update_status(struct osp_device *d, int rc) if (rc) goto out; - /* Add a bit of hysteresis so this flag isn't continually flapping, - * and ensure that new files don't get extremely fragmented due to - * only a small amount of available space in the filesystem. - * We want to set the NOSPC flag when there is less than ~0.1% free - * and clear it when there is at least ~0.2% free space, so: - * avail < ~0.1% max max = avail + used - * 1025 * avail < avail + used used = blocks - free - * 1024 * avail < used - * 1024 * avail < blocks - free - * avail < ((blocks - free) >> 10) - * - * On very large disk, say 16TB 0.1% will be 16 GB. We don't want to - * lose that amount of space so in those cases we report no space left - * if their is less than 1 GB left. */ if (likely(msfs->os_type)) { used = min_t(__u64, (msfs->os_blocks - msfs->os_bfree) >> 10, 1 << 30); @@ -803,6 +985,22 @@ out: wake_up(&d->opd_pre_user_waitq); } +/** + * Initialize FID for precreation + * + * For a just created new target, a new sequence should be taken. + * The function checks there is no IDIF in use (if the target was + * added with the older version of Lustre), then requests a new + * sequence from FLDB using the regular protocol. Then this new + * sequence is stored on a persisten storage synchronously to prevent + * possible object leakage (for the detail see the description for + * osp_precreate_rollover_new_seq()). + * + * \param[in] osp OSP device + * + * \retval 0 on success + * \retval negative negated errno on error + */ int osp_init_pre_fid(struct osp_device *osp) { struct lu_env env; @@ -859,6 +1057,24 @@ out: RETURN(rc); } +/** + * The core of precreate functionality + * + * The function implements the main precreation loop. Basically it + * involves connecting to the target, precerate FID initialization, + * identifying and removing orphans, then serving precreation. As + * part of the latter, the thread is responsible for statfs data + * updates. The precreation is mostly driven by another threads + * asking for new OST objects - those askers wake the thread when + * the number of precreated objects reach low watermark. + * After a disconnect, the sequence above repeats. This is keep going + * until the thread is requested to stop. + * + * \param[in] _arg private data the thread (OSP device to handle) + * + * \retval 0 on success + * \retval negative negated errno on error + */ static int osp_precreate_thread(void *_arg) { struct osp_device *d = _arg; @@ -985,6 +1201,20 @@ static int osp_precreate_thread(void *_arg) RETURN(0); } +/** + * Check when to stop to wait for precreate objects. + * + * The caller wanting a new OST object can't wait undefinitely. The + * function checks for few conditions including available new OST + * objects, disconnected OST, lack of space with no pending destroys, + * etc. IOW, it checks whether the current OSP state is good to keep + * waiting or it's better to give up. + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 - keep waiting, 1 - no luck + */ static int osp_precreate_ready_condition(const struct lu_env *env, struct osp_device *d) { @@ -1031,12 +1261,29 @@ static int osp_precreate_timeout_condition(void *data) return 1; } -/* - * called to reserve object in the pool - * return codes: - * ENOSPC - no space on corresponded OST - * EAGAIN - precreation is in progress, try later - * EIO - no access to OST +/** + * Reserve object in precreate pool + * + * When the caller wants to create a new object on this target (target + * represented by the given OSP), it should declare this intention using + * a regular ->dt_declare_create() OSD API method. Then OSP will be trying + * to reserve an object in the existing precreated pool or wait up to + * obd_timeout for the available object to appear in the pool (a dedicated + * thread will be doing real precreation in background). The object can be + * consumed later with osp_precreate_get_fid() or be released with call to + * lu_object_put(). Notice the function doesn't reserve a specific ID, just + * some ID. The actual ID assignment happen in osp_precreate_get_fid(). + * If the space on the target is short and there is a pending object destroy, + * then the function forces local commit to speedup space release (see + * osp_sync.c for the details). + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * + * \retval 0 on success + * \retval -ENOSPC when no space on OST + * \retval -EAGAIN try later, slow precreation in progress + * \retval -EIO when no access to OST */ int osp_precreate_reserve(const struct lu_env *env, struct osp_device *d) { @@ -1129,8 +1376,27 @@ int osp_precreate_reserve(const struct lu_env *env, struct osp_device *d) RETURN(rc); } -/* - * this function relies on reservation made before +/** + * Get a FID from precreation pool + * + * The function is a companion for osp_precreate_reserve() - it assigns + * a specific FID from the precreate. The function should be called only + * if the call to osp_precreate_reserve() was successful. The function + * updates a local storage to remember the highest object ID referenced + * by the node in the given sequence. + * + * A very importan details: this is supposed to be called once the + * transaction is started, so on-disk update will be atomic with the + * data (like LOVEA) refering this object. Then the object won't be leaked: + * either it's referenced by the committed transaction or it's a subject + * to the orphan cleanup procedure. + * + * \param[in] env LU environment provided by the caller + * \param[in] d OSP device + * \param[out] fid generated FID + * + * \retval 0 on success + * \retval negative negated errno on error */ int osp_precreate_get_fid(const struct lu_env *env, struct osp_device *d, struct lu_fid *fid) @@ -1166,7 +1432,20 @@ int osp_precreate_get_fid(const struct lu_env *env, struct osp_device *d, } /* + * Set size regular attribute on a object + * + * When a striping is created late, it's possible that size is already + * initialized on the file. Then the new striping should inherit size + * from the file. The function sets size on the object using the regular + * protocol (OST_PUNCH). + * XXX: should be re-implemented using OUT ? * + * \param[in] env LU environment provided by the caller + * \param[in] dt object + * \param[in] size size to set. + * + * \retval 0 on success + * \retval negative negated errno on error */ int osp_object_truncate(const struct lu_env *env, struct dt_object *dt, __u64 size) @@ -1235,6 +1514,16 @@ out: RETURN(rc); } +/** + * Initialize precreation functionality of OSP + * + * Prepares all the internal structures and starts the precreate thread + * + * \param[in] d OSP device + * + * \retval 0 on success + * \retval negative negated errno on error + */ int osp_init_precreate(struct osp_device *d) { struct l_wait_info lwi = { 0 }; @@ -1291,6 +1580,15 @@ int osp_init_precreate(struct osp_device *d) RETURN(0); } +/** + * Finish precreate functionality of OSP + * + * + * Asks all the activity (the thread, update timer) to stop, then + * wait till that is done. + * + * \param[in] d OSP device + */ void osp_precreate_fini(struct osp_device *d) { struct ptlrpc_thread *thread;