From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:42747) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h2HZt-0005k4-G7 for qemu-devel@nongnu.org; Fri, 08 Mar 2019 10:38:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h2HZr-0001d9-I9 for qemu-devel@nongnu.org; Fri, 08 Mar 2019 10:38:29 -0500 From: Kevin Wolf Date: Fri, 8 Mar 2019 16:37:56 +0100 Message-Id: <20190308153757.25794-8-kwolf@redhat.com> In-Reply-To: <20190308153757.25794-1-kwolf@redhat.com> References: <20190308153757.25794-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH 7/8] file-posix: Prepare permission code for fd switching List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, mreitz@redhat.com, eblake@redhat.com, pkrempa@redhat.com, qemu-devel@nongnu.org In order to be able to dynamically reopen the file read-only or read-write, depending on the users that are attached, we need to be able to switch to a different file descriptor during the permission change. This interacts with reopen, which also creates a new file descriptor and performs permission changes internally. In this case, the permission change code must reuse the reopen file descriptor instead of creating a third one. In turn, reopen can drop its code to copy file locks to the new file descriptor because that is now done when applying the new permissions. Signed-off-by: Kevin Wolf --- block/file-posix.c | 91 ++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 80 insertions(+), 11 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index 932cc8e58c..bcfb38ec4b 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -144,6 +144,7 @@ typedef struct BDRVRawState { uint64_t locked_perm; uint64_t locked_shared_perm; =20 + int perm_change_fd; BDRVReopenState *reopen_state; =20 #ifdef CONFIG_XFS @@ -845,7 +846,8 @@ static int raw_handle_perm_lock(BlockDriverState *bs, } =20 static int raw_reconfigure_getfd(BlockDriverState *bs, int flags, - int *open_flags, Error **errp) + int *open_flags, bool force_dup, + Error **errp) { BDRVRawState *s =3D bs->opaque; int fd =3D -1; @@ -871,6 +873,11 @@ static int raw_reconfigure_getfd(BlockDriverState *b= s, int flags, assert((s->open_flags & O_ASYNC) =3D=3D 0); #endif =20 + if (!force_dup && *open_flags =3D=3D s->open_flags) { + /* We're lucky, the existing fd is fine */ + return s->fd; + } + if ((*open_flags & ~fcntl_flags) =3D=3D (s->open_flags & ~fcntl_flag= s)) { /* dup the original fd */ fd =3D qemu_dup(s->fd); @@ -935,7 +942,7 @@ static int raw_reopen_prepare(BDRVReopenState *state, qemu_opts_to_qdict(opts, state->options); =20 rs->fd =3D raw_reconfigure_getfd(state->bs, state->flags, &rs->open_= flags, - &local_err); + true, &local_err); if (local_err) { error_propagate(errp, local_err); ret =3D -1; @@ -951,14 +958,6 @@ static int raw_reopen_prepare(BDRVReopenState *state= , ret =3D -EINVAL; goto out_fd; } - - /* Copy locks to the new fd */ - ret =3D raw_apply_lock_bytes(NULL, rs->fd, s->locked_perm, - s->locked_shared_perm, false, errp); - if (ret < 0) { - ret =3D -EINVAL; - goto out_fd; - } } =20 s->reopen_state =3D state; @@ -2696,12 +2695,73 @@ static QemuOptsList raw_create_opts =3D { static int raw_check_perm(BlockDriverState *bs, uint64_t perm, uint64_t = shared, Error **errp) { - return raw_handle_perm_lock(bs, RAW_PL_PREPARE, perm, shared, errp); + BDRVRawState *s =3D bs->opaque; + BDRVRawReopenState *rs =3D NULL; + int open_flags; + int ret; + + if (s->reopen_state) { + /* We already have a new file descriptor to set permissions for = */ + assert(s->reopen_state->perm =3D=3D perm); + assert(s->reopen_state->shared_perm =3D=3D shared); + if (s->perm_change_fd) { + /* reopen may call this function several times (directly and + * recursively while change permissions of the parent). Igno= re all + * but the first call. */ + return 0; + } + rs =3D s->reopen_state->opaque; + s->perm_change_fd =3D rs->fd; + } else { + /* We may need a new fd if auto-read-only switches the mode */ + assert(!s->perm_change_fd); + ret =3D raw_reconfigure_getfd(bs, bs->open_flags, &open_flags, + false, errp); + if (ret < 0) { + return ret; + } else if (ret !=3D s->fd) { + s->perm_change_fd =3D ret; + } + } + + /* Prepare permissions on old fd to avoid conflicts between old and = new, + * but keep everything locked that new will need. */ + ret =3D raw_handle_perm_lock(bs, RAW_PL_PREPARE, perm, shared, errp)= ; + if (ret < 0) { + goto fail; + } + + /* Copy locks to the new fd */ + if (s->perm_change_fd) { + ret =3D raw_apply_lock_bytes(NULL, s->perm_change_fd, perm, ~sha= red, + false, errp); + if (ret < 0) { + raw_handle_perm_lock(bs, RAW_PL_ABORT, 0, 0, NULL); + goto fail; + } + } + return 0; + +fail: + if (s->perm_change_fd && !s->reopen_state) { + qemu_close(s->perm_change_fd); + } + s->perm_change_fd =3D 0; + return ret; } =20 static void raw_set_perm(BlockDriverState *bs, uint64_t perm, uint64_t s= hared) { BDRVRawState *s =3D bs->opaque; + + /* For reopen, we have already switched to the new fd (.bdrv_set_per= m is + * called after .bdrv_reopen_commit) */ + if (s->perm_change_fd && s->fd !=3D s->perm_change_fd) { + qemu_close(s->fd); + s->fd =3D s->perm_change_fd; + } + s->perm_change_fd =3D 0; + raw_handle_perm_lock(bs, RAW_PL_COMMIT, perm, shared, NULL); s->perm =3D perm; s->shared_perm =3D shared; @@ -2709,6 +2769,15 @@ static void raw_set_perm(BlockDriverState *bs, uin= t64_t perm, uint64_t shared) =20 static void raw_abort_perm_update(BlockDriverState *bs) { + BDRVRawState *s =3D bs->opaque; + + /* For reopen, .bdrv_reopen_abort is called afterwards and will clos= e + * the file descriptor. */ + if (s->perm_change_fd && !s->reopen_state) { + qemu_close(s->perm_change_fd); + } + s->perm_change_fd =3D 0; + raw_handle_perm_lock(bs, RAW_PL_ABORT, 0, 0, NULL); } =20 --=20 2.20.1