I read through lib/seq.c to learn how this patch works. Looks good to me, but I feel not very confident.
Reviewed-by: Yifeng Sun <[email protected]> On Sun, Dec 31, 2017 at 9:16 PM, Ben Pfaff <[email protected]> wrote: > The OVSDB log code has always had the ability to commit the log to disk and > wait for the commit to finish. This patch introduces a new feature that > allows the client to start a commit in the background and then to determine > asynchronously that the commit has completed. This will be especially > useful later for the distributed database feature. > > Signed-off-by: Ben Pfaff <[email protected]> > --- > ovsdb/file.c | 4 +- > ovsdb/log.c | 152 ++++++++++++++++++++++++++++++ > +++++++++++++++++++++-- > ovsdb/log.h | 7 ++- > ovsdb/ovsdb-tool.c | 2 +- > tests/test-ovsdb.c | 2 +- > 5 files changed, 158 insertions(+), 9 deletions(-) > > diff --git a/ovsdb/file.c b/ovsdb/file.c > index 90c2b9d20a9a..fdd5f8e35a44 100644 > --- a/ovsdb/file.c > +++ b/ovsdb/file.c > @@ -661,7 +661,7 @@ ovsdb_file_compact(struct ovsdb_file *file) > > /* Commit the old version, so that we can be assured that we'll > eventually > * have either the old or the new version. */ > - error = ovsdb_log_commit(file->log); > + error = ovsdb_log_commit_block(file->log); > if (error) { > goto exit; > } > @@ -857,7 +857,7 @@ ovsdb_file_txn_commit(struct json *json, const char > *comment, > } > > if (durable) { > - error = ovsdb_log_commit(log); > + error = ovsdb_log_commit_block(log); > if (error) { > return ovsdb_wrap_error(error, "committing transaction > failed"); > } > diff --git a/ovsdb/log.c b/ovsdb/log.c > index 0f8dafa30a8f..cc4bc2c6243e 100644 > --- a/ovsdb/log.c > +++ b/ovsdb/log.c > @@ -24,12 +24,17 @@ > #include <sys/stat.h> > #include <unistd.h> > > +#include "lockfile.h" > #include "openvswitch/dynamic-string.h" > #include "openvswitch/json.h" > #include "openvswitch/vlog.h" > -#include "lockfile.h" > -#include "ovsdb.h" > +#include "ovs-atomic.h" > +#include "ovs-rcu.h" > +#include "ovs-thread.h" > #include "ovsdb-error.h" > +#include "ovsdb.h" > +#include "openvswitch/poll-loop.h" > +#include "seq.h" > #include "sha1.h" > #include "socket-util.h" > #include "transaction.h" > @@ -78,6 +83,7 @@ struct ovsdb_log { > struct lockfile *lockfile; > FILE *stream; > off_t base; > + struct afsync *afsync; > }; > > /* Whether the OS supports renaming open files. > @@ -95,6 +101,9 @@ static bool parse_header(char *header, const char > **magicp, > uint8_t sha1[SHA1_DIGEST_SIZE]); > static bool is_magic_ok(const char *needle, const char *haystack); > > +static struct afsync *afsync_create(int fd, uint64_t initial_ticket); > +static uint64_t afsync_destroy(struct afsync *); > + > /* Attempts to open 'name' with the specified 'open_mode'. On success, > stores > * the new log into '*filep' and returns NULL; otherwise returns NULL and > * stores NULL into '*filep'. > @@ -269,6 +278,7 @@ ovsdb_log_open(const char *name, const char *magic, > file->prev_offset = 0; > file->offset = 0; > file->base = 0; > + file->afsync = NULL; > *filep = file; > return NULL; > > @@ -308,6 +318,7 @@ ovsdb_log_close(struct ovsdb_log *file) > { > if (file) { > ovsdb_error_destroy(file->error); > + afsync_destroy(file->afsync); > free(file->name); > free(file->display_name); > free(file->magic); > @@ -634,8 +645,10 @@ ovsdb_log_write(struct ovsdb_log *file, const struct > json *json) > return NULL; > } > > +/* Attempts to commit 'file' to disk. Waits for the commit to succeed or > fail. > + * Returns NULL if successful, otherwise the error that occurred. */ > struct ovsdb_error * > -ovsdb_log_commit(struct ovsdb_log *file) > +ovsdb_log_commit_block(struct ovsdb_log *file) > { > if (file->stream && fsync(fileno(file->stream))) { > return ovsdb_io_error(errno, "%s: fsync failed", > file->display_name); > @@ -740,7 +753,7 @@ ovsdb_rename(const char *old, const char *new) > struct ovsdb_error * OVS_WARN_UNUSED_RESULT > ovsdb_log_replace_commit(struct ovsdb_log *old, struct ovsdb_log *new) > { > - struct ovsdb_error *error = ovsdb_log_commit(new); > + struct ovsdb_error *error = ovsdb_log_commit_block(new); > if (error) { > ovsdb_log_replace_abort(new); > return error; > @@ -812,6 +825,10 @@ ovsdb_log_replace_commit(struct ovsdb_log *old, > struct ovsdb_log *new) > ovsdb_error_destroy(old->error); > old->error = NULL; > /* prev_offset only matters for OVSDB_LOG_READ. */ > + if (old->afsync) { > + uint64_t ticket = afsync_destroy(old->afsync); > + old->afsync = afsync_create(fileno(old->stream), ticket + 1); > + } > old->offset = new->offset; > /* Keep old->name. */ > free(old->magic); > @@ -844,3 +861,130 @@ ovsdb_log_disable_renaming_open_files(void) > { > rename_open_files = false; > } > + > +struct afsync { > + pthread_t thread; > + atomic_uint64_t cur, next; > + struct seq *request, *complete; > + int fd; > +}; > + > +static void * > +afsync_thread(void *afsync_) > +{ > + struct afsync *afsync = afsync_; > + uint64_t cur = 0; > + for (;;) { > + ovsrcu_quiesce_start(); > + > + uint64_t request_seq = seq_read(afsync->request); > + > + uint64_t next; > + atomic_read_explicit(&afsync->next, &next, memory_order_acquire); > + if (next == UINT64_MAX) { > + break; > + } > + > + if (cur != next && afsync->fd != -1) { > + int error = fsync(afsync->fd) ? errno : 0; > + if (!error) { > + cur = next; > + atomic_store_explicit(&afsync->cur, cur, > memory_order_release); > + seq_change(afsync->complete); > + } else { > + VLOG_WARN("fsync failed (%s)", ovs_strerror(error)); > + } > + } > + > + seq_wait(afsync->request, request_seq); > + poll_block(); > + } > + return NULL; > +} > + > +static struct afsync * > +afsync_create(int fd, uint64_t initial_ticket) > +{ > + struct afsync *afsync = xzalloc(sizeof *afsync); > + atomic_init(&afsync->cur, initial_ticket); > + atomic_init(&afsync->next, initial_ticket); > + afsync->request = seq_create(); > + afsync->complete = seq_create(); > + afsync->thread = ovs_thread_create("log_fsync", afsync_thread, > afsync); > + afsync->fd = fd; > + return afsync; > +} > + > +static uint64_t > +afsync_destroy(struct afsync *afsync) > +{ > + if (!afsync) { > + return 0; > + } > + > + uint64_t next; > + atomic_read(&afsync->next, &next); > + atomic_store(&afsync->next, UINT64_MAX); > + seq_change(afsync->request); > + xpthread_join(afsync->thread, NULL); > + > + seq_destroy(afsync->request); > + seq_destroy(afsync->complete); > + > + free(afsync); > + > + return next; > +} > + > +static struct afsync * > +ovsdb_log_get_afsync(struct ovsdb_log *log) > +{ > + if (!log->afsync) { > + log->afsync = afsync_create(log->stream ? fileno(log->stream) : > -1, 0); > + } > + return log->afsync; > +} > + > +/* Starts committing 'log' to disk. Returns a ticket that can be passed > to > + * ovsdb_log_commit_wait() or compared against the return value of > + * ovsdb_log_commit_progress() later. */ > +uint64_t > +ovsdb_log_commit_start(struct ovsdb_log *log) > +{ > + struct afsync *afsync = ovsdb_log_get_afsync(log); > + > + uint64_t orig; > + atomic_add_explicit(&afsync->next, 1, &orig, memory_order_acq_rel); > + > + seq_change(afsync->request); > + > + return orig + 1; > +} > + > +/* Returns a ticket value that represents the current progress of commits > to > + * 'log'. Suppose that some call to ovsdb_log_commit_start() returns X > and any > + * call ovsdb_log_commit_progress() returns Y, for the same 'log'. Then > commit > + * X is complete if and only if X <= Y. */ > +uint64_t > +ovsdb_log_commit_progress(struct ovsdb_log *log) > +{ > + struct afsync *afsync = ovsdb_log_get_afsync(log); > + uint64_t cur; > + atomic_read_explicit(&afsync->cur, &cur, memory_order_acquire); > + return cur; > +} > + > +/* Causes poll_block() to wake up if and when > ovsdb_log_commit_progress(log) > + * would return at least 'goal'. */ > +void > +ovsdb_log_commit_wait(struct ovsdb_log *log, uint64_t goal) > +{ > + struct afsync *afsync = ovsdb_log_get_afsync(log); > + uint64_t complete = seq_read(afsync->complete); > + uint64_t cur = ovsdb_log_commit_progress(log); > + if (cur < goal) { > + seq_wait(afsync->complete, complete); > + } else { > + poll_immediate_wake(); > + } > +} > diff --git a/ovsdb/log.h b/ovsdb/log.h > index 18900fa50f44..bd0396f27ea8 100644 > --- a/ovsdb/log.h > +++ b/ovsdb/log.h > @@ -35,6 +35,7 @@ > * that compacting is advised. > */ > > +#include <stdint.h> > #include <sys/types.h> > #include "compiler.h" > > @@ -70,7 +71,11 @@ void ovsdb_log_compose_record(const struct json *, > const char *magic, > > struct ovsdb_error *ovsdb_log_write(struct ovsdb_log *, const struct json > *) > OVS_WARN_UNUSED_RESULT; > -struct ovsdb_error *ovsdb_log_commit(struct ovsdb_log *) > + > +uint64_t ovsdb_log_commit_start(struct ovsdb_log *); > +uint64_t ovsdb_log_commit_progress(struct ovsdb_log *); > +void ovsdb_log_commit_wait(struct ovsdb_log *, uint64_t); > +struct ovsdb_error *ovsdb_log_commit_block(struct ovsdb_log *) > OVS_WARN_UNUSED_RESULT; > > void ovsdb_log_mark_base(struct ovsdb_log *); > diff --git a/ovsdb/ovsdb-tool.c b/ovsdb/ovsdb-tool.c > index 4343e3ce5b22..cec64152f079 100644 > --- a/ovsdb/ovsdb-tool.c > +++ b/ovsdb/ovsdb-tool.c > @@ -222,7 +222,7 @@ do_create(struct ovs_cmdl_context *ctx) > check_ovsdb_error(ovsdb_log_open(db_file_name, OVSDB_MAGIC, > OVSDB_LOG_CREATE_EXCL, -1, &log)); > check_ovsdb_error(ovsdb_log_write(log, json)); > - check_ovsdb_error(ovsdb_log_commit(log)); > + check_ovsdb_error(ovsdb_log_commit_block(log)); > ovsdb_log_close(log); > > json_destroy(json); > diff --git a/tests/test-ovsdb.c b/tests/test-ovsdb.c > index 6b2cde863aba..c0c5a4df51af 100644 > --- a/tests/test-ovsdb.c > +++ b/tests/test-ovsdb.c > @@ -380,7 +380,7 @@ do_log_io(struct ovs_cmdl_context *ctx) > error = ovsdb_log_write(target, json); > json_destroy(json); > } else if (!strcmp(command, "commit")) { > - error = ovsdb_log_commit(target); > + error = ovsdb_log_commit_block(target); > } else if (!strcmp(command, "replace_start")) { > ovs_assert(!replacement); > error = ovsdb_log_replace_start(log, &replacement); > -- > 2.10.2 > > _______________________________________________ > dev mailing list > [email protected] > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
