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Mon, 11 Sep 2023 17:13:44 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 8MpGOshK/2QyIAAAMHmgww (envelope-from ); Mon, 11 Sep 2023 17:13:44 +0000 From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Juan Quintela , Peter Xu , Leonardo Bras Subject: [PATCH v6 10/10] migration: Add a wrapper to cleanup migration files Date: Mon, 11 Sep 2023 14:13:20 -0300 Message-Id: <20230911171320.24372-11-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20230911171320.24372-1-farosas@suse.de> References: <20230911171320.24372-1-farosas@suse.de> MIME-Version: 1.0 Received-SPF: pass client-ip=2001:67c:2178:6::1d; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org We currently have a pattern for cleaning up a migration QEMUFile: qemu_mutex_lock(&s->qemu_file_lock); file = s->file_name; s->file_name = NULL; qemu_mutex_unlock(&s->qemu_file_lock); migration_ioc_unregister_yank_from_file(file); qemu_file_shutdown(file); qemu_fclose(file); This sequence requires some consideration about locking to avoid TOC/TOU bugs and avoid passing NULL into the functions that don't expect it. There's no need to call a shutdown() right before a close() and a shutdown() in another thread being issued as a means to unblock a file should not collide with this close(). Create a wrapper function to make sure the locking is being done properly. Remove the extra shutdown(). Signed-off-by: Fabiano Rosas --- migration/migration.c | 89 ++++++++++++------------------------------- 1 file changed, 25 insertions(+), 64 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index 7fec57ad7f..3e94521321 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -217,6 +217,26 @@ MigrationIncomingState *migration_incoming_get_current(void) return current_incoming; } +static void migration_file_release(QEMUFile **file) +{ + MigrationState *ms = migrate_get_current(); + QEMUFile *tmp; + + /* + * Reset the pointer before releasing it to avoid holding the lock + * for too long. + */ + WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) { + tmp = *file; + *file = NULL; + } + + if (tmp) { + migration_ioc_unregister_yank_from_file(tmp); + qemu_fclose(tmp); + } +} + void migration_incoming_transport_cleanup(MigrationIncomingState *mis) { if (mis->socket_address_list) { @@ -1155,8 +1175,6 @@ static void migrate_fd_cleanup(MigrationState *s) qemu_savevm_state_cleanup(); if (s->to_dst_file) { - QEMUFile *tmp; - trace_migrate_fd_cleanup(); qemu_mutex_unlock_iothread(); if (s->migration_thread_running) { @@ -1166,16 +1184,7 @@ static void migrate_fd_cleanup(MigrationState *s) qemu_mutex_lock_iothread(); multifd_save_cleanup(); - qemu_mutex_lock(&s->qemu_file_lock); - tmp = s->to_dst_file; - s->to_dst_file = NULL; - qemu_mutex_unlock(&s->qemu_file_lock); - /* - * Close the file handle without the lock to make sure the - * critical section won't block for long. - */ - migration_ioc_unregister_yank_from_file(tmp); - qemu_fclose(tmp); + migration_file_release(&s->to_dst_file); } /* @@ -1815,38 +1824,6 @@ static int migrate_handle_rp_resume_ack(MigrationState *s, uint32_t value) return 0; } -/* - * Release ms->rp_state.from_dst_file (and postcopy_qemufile_src if - * existed) in a safe way. - */ -static void migration_release_dst_files(MigrationState *ms) -{ - QEMUFile *file; - - WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) { - /* - * Reset the from_dst_file pointer first before releasing it, as we - * can't block within lock section - */ - file = ms->rp_state.from_dst_file; - ms->rp_state.from_dst_file = NULL; - } - - /* - * Do the same to postcopy fast path socket too if there is. No - * locking needed because this qemufile should only be managed by - * return path thread. - */ - if (ms->postcopy_qemufile_src) { - migration_ioc_unregister_yank_from_file(ms->postcopy_qemufile_src); - qemu_file_shutdown(ms->postcopy_qemufile_src); - qemu_fclose(ms->postcopy_qemufile_src); - ms->postcopy_qemufile_src = NULL; - } - - qemu_fclose(file); -} - /* * Handles messages sent on the return path towards the source VM * @@ -2046,7 +2023,8 @@ static int await_return_path_close_on_source(MigrationState *ms) ret = ms->rp_state.error; ms->rp_state.error = false; - migration_release_dst_files(ms); + migration_file_release(&ms->rp_state.from_dst_file); + migration_file_release(&ms->postcopy_qemufile_src); trace_migration_return_path_end_after(ret); return ret; @@ -2502,26 +2480,9 @@ static MigThrError postcopy_pause(MigrationState *s) assert(s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE); while (true) { - QEMUFile *file; - - /* - * Current channel is possibly broken. Release it. Note that this is - * guaranteed even without lock because to_dst_file should only be - * modified by the migration thread. That also guarantees that the - * unregister of yank is safe too without the lock. It should be safe - * even to be within the qemu_file_lock, but we didn't do that to avoid - * taking more mutex (yank_lock) within qemu_file_lock. TL;DR: we make - * the qemu_file_lock critical section as small as possible. - */ + /* Current channel is possibly broken. Release it. */ assert(s->to_dst_file); - migration_ioc_unregister_yank_from_file(s->to_dst_file); - qemu_mutex_lock(&s->qemu_file_lock); - file = s->to_dst_file; - s->to_dst_file = NULL; - qemu_mutex_unlock(&s->qemu_file_lock); - - qemu_file_shutdown(file); - qemu_fclose(file); + migration_file_release(&s->to_dst_file); /* * We're already pausing, so ignore any errors on the return