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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 11/13] block: Add block layer notifications [ver #4] From: David Howells To: viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, raven@themaw.net, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-block@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 07 Jun 2019 15:19:04 +0100 Message-ID: <155991714448.15579.1960242962075486353.stgit@warthog.procyon.org.uk> In-Reply-To: <155991702981.15579.6007568669839441045.stgit@warthog.procyon.org.uk> References: <155991702981.15579.6007568669839441045.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 07 Jun 2019 14:19:09 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add a block layer notification mechanism whereby notifications about block-layer events such as I/O errors, can be reported to a monitoring process asynchronously. Firstly, an event queue needs to be created: fd = open("/dev/event_queue", O_RDWR); ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, page_size << n); then a notification can be set up to report block notifications via that queue: struct watch_notification_filter filter = { .nr_filters = 1, .filters = { [0] = { .type = WATCH_TYPE_BLOCK_NOTIFY, .subtype_filter[0] = UINT_MAX; }, }, }; ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter); watch_devices(fd, 12); After that, records will be placed into the queue when, for example, errors occur on a block device. Records are of the following format: struct block_notification { struct watch_notification watch; __u64 dev; __u64 sector; } *n; Where: n->watch.type will be WATCH_TYPE_BLOCK_NOTIFY n->watch.subtype will be the type of notification, such as NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM. n->watch.info & WATCH_INFO_LENGTH will indicate the length of the record. n->watch.info & WATCH_INFO_ID will be the second argument to watch_devices(), shifted. n->dev will be the device numbers munged together. n->sector will indicate the affected sector (if appropriate for the event). Note that it is permissible for event records to be of variable length - or, at least, the length may be dependent on the subtype. Signed-off-by: David Howells --- Documentation/watch_queue.rst | 10 +++++++++- block/Kconfig | 9 +++++++++ block/blk-core.c | 29 +++++++++++++++++++++++++++++ include/linux/blkdev.h | 15 +++++++++++++++ include/uapi/linux/watch_queue.h | 27 +++++++++++++++++++++++++++ 5 files changed, 89 insertions(+), 1 deletion(-) diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst index e4b8233d5aa8..c2954e191989 100644 --- a/Documentation/watch_queue.rst +++ b/Documentation/watch_queue.rst @@ -11,7 +11,9 @@ receive notifications from the kernel. This can be used in conjunction with:: * Superblock event notifications - * General device event notifications + * General device event notifications, including:: + + * Block layer event notifications The notifications buffers can be enabled by: @@ -336,6 +338,12 @@ Any particular buffer can be fed from multiple sources. Sources include: See Documentation/security/keys/core.rst for more information. + * WATCH_TYPE_BLOCK_NOTIFY + + Notifications of this type indicate block layer events, such as I/O errors + or temporary link loss. Watchpoints of this type are set on the global + device watch list. + Event Filtering =============== diff --git a/block/Kconfig b/block/Kconfig index 1b220101a9cb..4ff4a56ba9f9 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -163,6 +163,15 @@ config BLK_SED_OPAL Enabling this option enables users to setup/unlock/lock Locking ranges for SED devices using the Opal protocol. +config BLK_NOTIFICATIONS + bool "Block layer event notifications" + select DEVICE_NOTIFICATIONS + help + This option provides support for getting block layer event + notifications. This makes use of the /dev/watch_queue misc device to + handle the notification buffer and provides the device_notify() system + call to enable/disable watches. + menu "Partition Types" source "block/partitions/Kconfig" diff --git a/block/blk-core.c b/block/blk-core.c index 419d600e6637..edad86172d47 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -144,6 +144,22 @@ static const struct { [BLK_STS_IOERR] = { -EIO, "I/O" }, }; +#ifdef CONFIG_BLK_NOTIFICATIONS +static const +enum block_notification_type blk_notifications[ARRAY_SIZE(blk_errors)] = { + [BLK_STS_TIMEOUT] = NOTIFY_BLOCK_ERROR_TIMEOUT, + [BLK_STS_NOSPC] = NOTIFY_BLOCK_ERROR_NO_SPACE, + [BLK_STS_TRANSPORT] = NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT, + [BLK_STS_TARGET] = NOTIFY_BLOCK_ERROR_CRITICAL_TARGET, + [BLK_STS_NEXUS] = NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS, + [BLK_STS_MEDIUM] = NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM, + [BLK_STS_PROTECTION] = NOTIFY_BLOCK_ERROR_PROTECTION, + [BLK_STS_RESOURCE] = NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE, + [BLK_STS_DEV_RESOURCE] = NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE, + [BLK_STS_IOERR] = NOTIFY_BLOCK_ERROR_IO, +}; +#endif + blk_status_t errno_to_blk_status(int errno) { int i; @@ -179,6 +195,19 @@ static void print_req_error(struct request *req, blk_status_t status) req->rq_disk ? req->rq_disk->disk_name : "?", (unsigned long long)blk_rq_pos(req), req->cmd_flags); + +#ifdef CONFIG_BLK_NOTIFICATIONS + if (blk_notifications[idx]) { + struct block_notification n = { + .watch.type = WATCH_TYPE_BLOCK_NOTIFY, + .watch.subtype = blk_notifications[idx], + .watch.info = sizeof(n), + .dev = req->rq_disk ? disk_devt(req->rq_disk) : 0, + .sector = blk_rq_pos(req), + }; + post_block_notification(&n); + } +#endif } static void req_bio_endio(struct request *rq, struct bio *bio, diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 1aafeb923e7b..8b8e235f47c9 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -43,6 +43,7 @@ struct pr_ops; struct rq_qos; struct blk_queue_stats; struct blk_stat_callback; +struct block_notification; #define BLKDEV_MIN_RQ 4 #define BLKDEV_MAX_RQ 128 /* Default maximum */ @@ -1744,6 +1745,20 @@ static inline bool blk_req_can_dispatch_to_zone(struct request *rq) } #endif /* CONFIG_BLK_DEV_ZONED */ +#ifdef CONFIG_BLK_NOTIFICATIONS +static inline void post_block_notification(struct block_notification *n) +{ + u64 id = 0; /* Might want to allow dev# here. */ + + post_device_notification(&n->watch, id); +} +#else +static inline void post_block_notification(struct block_notification *n) +{ +} +#endif + + #else /* CONFIG_BLOCK */ struct block_device; diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h index aeffcfd7a742..22e3326b83a6 100644 --- a/include/uapi/linux/watch_queue.h +++ b/include/uapi/linux/watch_queue.h @@ -155,4 +155,31 @@ struct superblock_error_notification { __u32 error_cookie; }; +/* + * Type of block layer notification. + */ +enum block_notification_type { + NOTIFY_BLOCK_ERROR_TIMEOUT = 1, /* Timeout error */ + NOTIFY_BLOCK_ERROR_NO_SPACE = 2, /* Critical space allocation error */ + NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT = 3, /* Recoverable transport error */ + NOTIFY_BLOCK_ERROR_CRITICAL_TARGET = 4, /* Critical target error */ + NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS = 5, /* Critical nexus error */ + NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM = 6, /* Critical medium error */ + NOTIFY_BLOCK_ERROR_PROTECTION = 7, /* Protection error */ + NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE = 8, /* Kernel resource error */ + NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE = 9, /* Device resource error */ + NOTIFY_BLOCK_ERROR_IO = 10, /* Other I/O error */ +}; + +/* + * Block layer notification record. + * - watch.type = WATCH_TYPE_BLOCK_NOTIFY + * - watch.subtype = enum block_notification_type + */ +struct block_notification { + struct watch_notification watch; /* WATCH_TYPE_BLOCK_NOTIFY */ + __u64 dev; /* Device number */ + __u64 sector; /* Affected sector */ +}; + #endif /* _UAPI_LINUX_WATCH_QUEUE_H */