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spf=pass smtp.mailfrom=pbonzini@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com CE3B5C0B39E4 From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Thu, 25 May 2017 18:32:08 +0200 Message-Id: <20170525163225.29954-2-pbonzini@redhat.com> In-Reply-To: <20170525163225.29954-1-pbonzini@redhat.com> References: <20170525163225.29954-1-pbonzini@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 25 May 2017 16:32:30 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 01/18] block: access copy_on_read with atomic ops X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: famz@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Reviewed-by: Stefan Hajnoczi Signed-off-by: Paolo Bonzini --- block.c | 6 ++++-- block/io.c | 8 ++++---- blockdev.c | 2 +- include/block/block_int.h | 11 ++++++----- 4 files changed, 15 insertions(+), 12 deletions(-) diff --git a/block.c b/block.c index 50ba264..f6066ef 100644 --- a/block.c +++ b/block.c @@ -1260,7 +1260,9 @@ static int bdrv_open_common(BlockDriverState *bs, Blo= ckBackend *file, goto fail_opts; } =20 - assert(bs->copy_on_read =3D=3D 0); /* bdrv_new() and bdrv_close() make= it so */ + /* bdrv_new() and bdrv_close() make it so */ + assert(atomic_read(&bs->copy_on_read) =3D=3D 0); + if (bs->open_flags & BDRV_O_COPY_ON_READ) { if (!bs->read_only) { bdrv_enable_copy_on_read(bs); @@ -3023,7 +3025,7 @@ static void bdrv_close(BlockDriverState *bs) =20 g_free(bs->opaque); bs->opaque =3D NULL; - bs->copy_on_read =3D 0; + atomic_set(&bs->copy_on_read, 0); bs->backing_file[0] =3D '\0'; bs->backing_format[0] =3D '\0'; bs->total_sectors =3D 0; diff --git a/block/io.c b/block/io.c index fdd7485..80a3a8c 100644 --- a/block/io.c +++ b/block/io.c @@ -129,13 +129,13 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error = **errp) */ void bdrv_enable_copy_on_read(BlockDriverState *bs) { - bs->copy_on_read++; + atomic_inc(&bs->copy_on_read); } =20 void bdrv_disable_copy_on_read(BlockDriverState *bs) { - assert(bs->copy_on_read > 0); - bs->copy_on_read--; + int old =3D atomic_fetch_dec(&bs->copy_on_read); + assert(old >=3D 1); } =20 /* Check if any requests are in-flight (including throttled requests) */ @@ -1157,7 +1157,7 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child, bdrv_inc_in_flight(bs); =20 /* Don't do copy-on-read if we read data before write operation */ - if (bs->copy_on_read && !(flags & BDRV_REQ_NO_SERIALISING)) { + if (atomic_read(&bs->copy_on_read) && !(flags & BDRV_REQ_NO_SERIALISIN= G)) { flags |=3D BDRV_REQ_COPY_ON_READ; } =20 diff --git a/blockdev.c b/blockdev.c index c63f4e8..a2fa9f7 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1791,7 +1791,7 @@ static void external_snapshot_commit(BlkActionState *= common) /* We don't need (or want) to use the transactional * bdrv_reopen_multiple() across all the entries at once, because we * don't want to abort all of them if one of them fails the reopen */ - if (!state->old_bs->copy_on_read) { + if (!atomic_read(&state->old_bs->copy_on_read)) { bdrv_reopen(state->old_bs, state->old_bs->open_flags & ~BDRV_O_RDW= R, NULL); } diff --git a/include/block/block_int.h b/include/block/block_int.h index 8d3724c..c71492a 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -595,11 +595,6 @@ struct BlockDriverState { =20 /* Protected by AioContext lock */ =20 - /* If true, copy read backing sectors into image. Can be >1 if more - * than one client has requested copy-on-read. - */ - int copy_on_read; - /* If we are reading a disk image, give its size in sectors. * Generally read-only; it is written to by load_vmstate and save_vmst= ate, * but the block layer is quiescent during those. @@ -633,6 +628,12 @@ struct BlockDriverState { =20 QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps; =20 + /* If true, copy read backing sectors into image. Can be >1 if more + * than one client has requested copy-on-read. Accessed with atomic + * ops. + */ + int copy_on_read; + /* do we need to tell the quest if we have a volatile write cache? */ int enable_write_cache; =20 --=20 1.8.3.1