From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:36455) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QgYMj-0007yN-4z for qemu-devel@nongnu.org; Tue, 12 Jul 2011 04:30:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QgYMe-0008Cw-S3 for qemu-devel@nongnu.org; Tue, 12 Jul 2011 04:30:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5127) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QgYMe-0008Cq-E7 for qemu-devel@nongnu.org; Tue, 12 Jul 2011 04:30:44 -0400 Message-ID: <4E1C06DF.2050302@redhat.com> Date: Tue, 12 Jul 2011 10:33:35 +0200 From: Kevin Wolf MIME-Version: 1.0 References: <1309889871-6267-1-git-send-email-lcapitulino@redhat.com> <1309889871-6267-4-git-send-email-lcapitulino@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 3/8] block: Support to keep track of I/O status List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: stefanha@gmail.com, jan.kiszka@siemens.com, jdenemar@redhat.com, qemu-devel@nongnu.org, Luiz Capitulino Am 12.07.2011 09:45, schrieb Markus Armbruster: > Luiz Capitulino writes: > >> This commit adds support to the BlockDriverState type to keep track >> of the last I/O status. That is, at every I/O operation we update >> a status field in the BlockDriverState instance. Valid statuses are: >> OK, FAILED and ENOSPC. >> >> ENOSPC is distinguished from FAILED because an management application >> can use it to implement thin-provisioning. >> >> This feature has to be explicit enabled by buses/devices supporting it. > > buses? > >> >> Signed-off-by: Luiz Capitulino >> --- >> block.c | 18 ++++++++++++++++++ >> block.h | 7 +++++++ >> block_int.h | 2 ++ >> 3 files changed, 27 insertions(+), 0 deletions(-) >> >> diff --git a/block.c b/block.c >> index 24a25d5..cc0a34e 100644 >> --- a/block.c >> +++ b/block.c >> @@ -195,6 +195,7 @@ BlockDriverState *bdrv_new(const char *device_name) >> if (device_name[0] != '\0') { >> QTAILQ_INSERT_TAIL(&bdrv_states, bs, list); >> } >> + bs->iostatus_enabled = false; >> return bs; >> } >> >> @@ -2876,6 +2877,23 @@ int bdrv_in_use(BlockDriverState *bs) >> return bs->in_use; >> } >> >> +void bdrv_enable_iostatus(BlockDriverState *bs) >> +{ >> + bs->iostatus_enabled = true; >> +} >> + >> +void bdrv_iostatus_update(BlockDriverState *bs, int error) >> +{ >> + error = abs(error); >> + >> + if (!error) { >> + bs->iostatus = BDRV_IOS_OK; >> + } else { >> + bs->iostatus = (error == ENOSPC) ? BDRV_IOS_ENOSPC : >> + BDRV_IOS_FAILED; >> + } >> +} >> + >> int bdrv_img_create(const char *filename, const char *fmt, >> const char *base_filename, const char *base_fmt, >> char *options, uint64_t img_size, int flags) >> diff --git a/block.h b/block.h >> index 859d1d9..0dca1bb 100644 >> --- a/block.h >> +++ b/block.h >> @@ -50,6 +50,13 @@ typedef enum { >> BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP >> } BlockMonEventAction; >> >> +typedef enum { >> + BDRV_IOS_OK, BDRV_IOS_FAILED, BDRV_IOS_ENOSPC >> +} BlockIOStatus; >> + >> +void bdrv_iostatus_update(BlockDriverState *bs, int error); >> +void bdrv_enable_iostatus(BlockDriverState *bs); >> +void bdrv_enable_io_status(BlockDriverState *bs); >> void bdrv_mon_event(const BlockDriverState *bdrv, >> BlockMonEventAction action, int is_read); >> void bdrv_info_print(Monitor *mon, const QObject *data); >> diff --git a/block_int.h b/block_int.h >> index 1e265d2..09f038d 100644 >> --- a/block_int.h >> +++ b/block_int.h >> @@ -195,6 +195,8 @@ struct BlockDriverState { >> drivers. They are not used by the block driver */ >> int cyls, heads, secs, translation; >> BlockErrorAction on_read_error, on_write_error; >> + bool iostatus_enabled; >> + BlockIOStatus iostatus; >> char device_name[32]; >> unsigned long *dirty_bitmap; >> int64_t dirty_count; > > Okay, let's see what we got here. > > The block layer merely holds I/O status, device models set it. > > Device I/O status is not migrated. Why? > > bdrv_new() creates the BDS with I/O status tracking disabled. Devices > that do tracking enable it in their qdev init method. If a device gets > hot unplugged, tracking remains enabled. If the BDS then gets reused > with a device that doesn't do tracking, I/O status becomes incorrect. > Can't happen right now, because we automatically delete the BDS on hot > unplug, but it's a trap. Suggest to disable tracking in bdrv_detach(). > > Actually, this is a symptom of the midlayer disease. I suspect things > would be simpler if we hold the status in its rightful owner, the device > model. Need a getter for it. I'm working on a patch series that moves > misplaced state out of the block layer into device models and block > drivers, and a I/O status getter will fit in easily there. This is host state, so the device is not the rightful owner. Devices should not even be involved with enabling it. Kevin