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X-Received-From: 2607:f8b0:400e:c01::243 Subject: [Qemu-devel] [PATCH v4] linux-aio: properly bubble up errors from initialization 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: , From: Nishanth Aravamudan via Qemu-devel Reply-To: Nishanth Aravamudan Cc: Kevin Wolf , Fam Zheng , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Stefan Hajnoczi , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" laio_init() can fail for a couple of reasons, which will lead to a NULL pointer dereference in laio_attach_aio_context(). To solve this, add a aio_setup_linux_aio() function which is called early in raw_open_common. If this fails, propagate the error up. The signature of aio_get_linux_aio() was not modified, because it seems preferable to return the actual errno from the possible failing initialization calls. Additionally, when the AioContext changes, we need to associate a LinuxAioState with the new AioContext. Use the bdrv_attach_aio_context callback and call the new aio_setup_linux_aio(), which will allocate a new AioContext if needed, and return errors on failures. If it fails for any reason, fallback to threaded AIO with an error message, as the device is already in-use by the guest. Add an assert that aio_get_linux_aio() cannot return NULL. Signed-off-by: Nishanth Aravamudan --- Test case 1: Set /proc/sys/fs/max-aio-nr to 0. Start a guest with an aio=3Dnative disk. Result: laio_init() returns NULL due to not being able to allocate any AIO contexts. This NULL is assigned to ctx->linux_aio and dereferenced in aio_get_linux_aio. Test case 2: Set /proc/sys/fs/max-aio-nr to 128. Start a guest with an aio=3Dnative disk and one in-use I/O thread. Result: laio_init() returns NULL due to not being able to allocate additional AIO contexts for the I/O thread. This NULL is assigned to ctx->linux_aio and dereferenced in aio_get_linux_aio. Changes from v3 -> v4 (thanks to Fam Zheng and Kevin Wolf for review): Squash patch 2/2 into 1/2. Differentiate the possible reasons for laio_init() failing and use an Error ** to propagate the errno to the caller. Changes from v2 -> v3 (thanks to Eric Blake and Kevin Wolf for review): Use a boolean false rather than 0 in assignment to use_linux_aio. Drop ending '.' from error_report() calls. Fix typo in commit message (propogates -> propagates). Move aio_setup_linux_aio call to raw_open_common. Changes from v1 -> v2 (thanks to Kevin Wolf for review): Rather than affect virtio-scsi/blk at all, make all the changes internal to file-posix.c. Thanks to Kevin Wolf for the suggested change. block/file-posix.c | 33 ++++++++++++++++++++++++++++----- block/linux-aio.c | 12 +++++++++--- include/block/aio.h | 3 +++ include/block/raw-aio.h | 2 +- stubs/linux-aio.c | 2 +- util/async.c | 14 +++++++++++--- 6 files changed, 53 insertions(+), 13 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index 07bb061fe4..43b963b13e 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -545,11 +545,17 @@ static int raw_open_common(BlockDriverState *bs, QDic= t *options, =20 #ifdef CONFIG_LINUX_AIO /* Currently Linux does AIO only for files opened with O_DIRECT */ - if (s->use_linux_aio && !(s->open_flags & O_DIRECT)) { - error_setg(errp, "aio=3Dnative was specified, but it requires " - "cache.direct=3Don, which was not specified."); - ret =3D -EINVAL; - goto fail; + if (s->use_linux_aio) { + if (!(s->open_flags & O_DIRECT)) { + error_setg(errp, "aio=3Dnative was specified, but it requires " + "cache.direct=3Don, which was not specified."= ); + ret =3D -EINVAL; + goto fail; + } + if (!aio_setup_linux_aio(bdrv_get_aio_context(bs), errp)) { + error_prepend(errp, "Unable to use native AIO: "); + goto fail; + } } #else if (s->use_linux_aio) { @@ -1723,6 +1729,22 @@ static BlockAIOCB *raw_aio_flush(BlockDriverState *b= s, return paio_submit(bs, s->fd, 0, NULL, 0, cb, opaque, QEMU_AIO_FLUSH); } =20 +static void raw_aio_attach_aio_context(BlockDriverState *bs, + AioContext *new_context) +{ +#ifdef CONFIG_LINUX_AIO + BDRVRawState *s =3D bs->opaque; + if (s->use_linux_aio) { + Error *local_err; + if (!aio_setup_linux_aio(new_context, &local_err)) { + error_reportf_err(local_err, "Unable to use native AIO, " + "falling back to thread pool: "); + s->use_linux_aio =3D false; + } + } +#endif +} + static void raw_close(BlockDriverState *bs) { BDRVRawState *s =3D bs->opaque; @@ -2601,6 +2623,7 @@ BlockDriver bdrv_file =3D { .bdrv_refresh_limits =3D raw_refresh_limits, .bdrv_io_plug =3D raw_aio_plug, .bdrv_io_unplug =3D raw_aio_unplug, + .bdrv_attach_aio_context =3D raw_aio_attach_aio_context, =20 .bdrv_truncate =3D raw_truncate, .bdrv_getlength =3D raw_getlength, diff --git a/block/linux-aio.c b/block/linux-aio.c index 88b8d55ec7..19eb922fdd 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -15,6 +15,7 @@ #include "block/raw-aio.h" #include "qemu/event_notifier.h" #include "qemu/coroutine.h" +#include "qapi/error.h" =20 #include =20 @@ -470,16 +471,21 @@ void laio_attach_aio_context(LinuxAioState *s, AioCon= text *new_context) qemu_laio_poll_cb); } =20 -LinuxAioState *laio_init(void) +LinuxAioState *laio_init(Error **errp) { + int rc; LinuxAioState *s; =20 s =3D g_malloc0(sizeof(*s)); - if (event_notifier_init(&s->e, false) < 0) { + rc =3D event_notifier_init(&s->e, false); + if (rc < 0) { + error_setg_errno(errp, -rc, "failed to to initialize event notifie= r"); goto out_free_state; } =20 - if (io_setup(MAX_EVENTS, &s->ctx) !=3D 0) { + rc =3D io_setup(MAX_EVENTS, &s->ctx); + if (rc < 0) { + error_setg_errno(errp, -rc, "failed to create linux AIO context"); goto out_close_efd; } =20 diff --git a/include/block/aio.h b/include/block/aio.h index ae6f354e6c..f08630c6e5 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -381,6 +381,9 @@ GSource *aio_get_g_source(AioContext *ctx); /* Return the ThreadPool bound to this AioContext */ struct ThreadPool *aio_get_thread_pool(AioContext *ctx); =20 +/* Setup the LinuxAioState bound to this AioContext */ +struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp); + /* Return the LinuxAioState bound to this AioContext */ struct LinuxAioState *aio_get_linux_aio(AioContext *ctx); =20 diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h index 0e717fd475..8d698ccd31 100644 --- a/include/block/raw-aio.h +++ b/include/block/raw-aio.h @@ -43,7 +43,7 @@ /* linux-aio.c - Linux native implementation */ #ifdef CONFIG_LINUX_AIO typedef struct LinuxAioState LinuxAioState; -LinuxAioState *laio_init(void); +LinuxAioState *laio_init(Error **errp); void laio_cleanup(LinuxAioState *s); int coroutine_fn laio_co_submit(BlockDriverState *bs, LinuxAioState *s, in= t fd, uint64_t offset, QEMUIOVector *qiov, int t= ype); diff --git a/stubs/linux-aio.c b/stubs/linux-aio.c index ed47bd443c..84d1f784ae 100644 --- a/stubs/linux-aio.c +++ b/stubs/linux-aio.c @@ -21,7 +21,7 @@ void laio_attach_aio_context(LinuxAioState *s, AioContext= *new_context) abort(); } =20 -LinuxAioState *laio_init(void) +LinuxAioState *laio_init(Error **errp) { abort(); } diff --git a/util/async.c b/util/async.c index 03f62787f2..05979f8014 100644 --- a/util/async.c +++ b/util/async.c @@ -323,14 +323,22 @@ ThreadPool *aio_get_thread_pool(AioContext *ctx) } =20 #ifdef CONFIG_LINUX_AIO -LinuxAioState *aio_get_linux_aio(AioContext *ctx) +LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp) { if (!ctx->linux_aio) { - ctx->linux_aio =3D laio_init(); - laio_attach_aio_context(ctx->linux_aio, ctx); + ctx->linux_aio =3D laio_init(errp); + if (ctx->linux_aio) { + laio_attach_aio_context(ctx->linux_aio, ctx); + } } return ctx->linux_aio; } + +LinuxAioState *aio_get_linux_aio(AioContext *ctx) +{ + assert(ctx->linux_aio); + return ctx->linux_aio; +} #endif =20 void aio_notify(AioContext *ctx) --=20 2.17.1