Date: Sun, 21 Feb 2021 00:43:15 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: a15f787adb44 - main - vfs: add vfs_ref_from_vp Message-ID: <202102210043.11L0hFhg074698@gitrepo.freebsd.org>
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The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=a15f787adb4429b83fa911dcb60f69121aaee1ba commit a15f787adb4429b83fa911dcb60f69121aaee1ba Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2021-02-15 22:08:40 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2021-02-21 00:43:05 +0000 vfs: add vfs_ref_from_vp This generalizes what vop_stdgetwritemount used to be doing. Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D28695 --- sys/kern/vfs_default.c | 25 +------------------------ sys/kern/vfs_mount.c | 38 ++++++++++++++++++++++++++++++++++++++ sys/sys/mount.h | 1 + 3 files changed, 40 insertions(+), 24 deletions(-) diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c index 3c428d7b7511..4b9b1b43f1ce 100644 --- a/sys/kern/vfs_default.c +++ b/sys/kern/vfs_default.c @@ -680,7 +680,6 @@ vop_stdgetwritemount(ap) } */ *ap; { struct mount *mp; - struct mount_pcpu *mpcpu; struct vnode *vp; /* @@ -693,29 +692,7 @@ vop_stdgetwritemount(ap) * with releasing it. */ vp = ap->a_vp; - mp = vp->v_mount; - if (mp == NULL) { - *(ap->a_mpp) = NULL; - return (0); - } - if (vfs_op_thread_enter(mp, mpcpu)) { - if (mp == vp->v_mount) { - vfs_mp_count_add_pcpu(mpcpu, ref, 1); - vfs_op_thread_exit(mp, mpcpu); - } else { - vfs_op_thread_exit(mp, mpcpu); - mp = NULL; - } - } else { - MNT_ILOCK(mp); - if (mp == vp->v_mount) { - MNT_REF(mp); - MNT_IUNLOCK(mp); - } else { - MNT_IUNLOCK(mp); - mp = NULL; - } - } + mp = vfs_ref_from_vp(vp); *(ap->a_mpp) = mp; return (0); } diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c index b3870e46c5e9..e20e1520f677 100644 --- a/sys/kern/vfs_mount.c +++ b/sys/kern/vfs_mount.c @@ -449,6 +449,44 @@ sys_nmount(struct thread *td, struct nmount_args *uap) * Various utility functions */ +/* + * Get a reference on a mount point from a vnode. + * + * The vnode is allowed to be passed unlocked and race against dooming. Note in + * such case there are no guarantees the referenced mount point will still be + * associated with it after the function returns. + */ +struct mount * +vfs_ref_from_vp(struct vnode *vp) +{ + struct mount *mp; + struct mount_pcpu *mpcpu; + + mp = atomic_load_ptr(&vp->v_mount); + if (__predict_false(mp == NULL)) { + return (mp); + } + if (vfs_op_thread_enter(mp, mpcpu)) { + if (__predict_true(mp == vp->v_mount)) { + vfs_mp_count_add_pcpu(mpcpu, ref, 1); + vfs_op_thread_exit(mp, mpcpu); + } else { + vfs_op_thread_exit(mp, mpcpu); + mp = NULL; + } + } else { + MNT_ILOCK(mp); + if (mp == vp->v_mount) { + MNT_REF(mp); + MNT_IUNLOCK(mp); + } else { + MNT_IUNLOCK(mp); + mp = NULL; + } + } + return (mp); +} + void vfs_ref(struct mount *mp) { diff --git a/sys/sys/mount.h b/sys/sys/mount.h index f965dd72d7ba..9ae5f58e5218 100644 --- a/sys/sys/mount.h +++ b/sys/sys/mount.h @@ -997,6 +997,7 @@ void vfs_mount_error(struct mount *, const char *, ...); void vfs_mountroot(void); /* mount our root filesystem */ void vfs_mountedfrom(struct mount *, const char *from); void vfs_notify_upper(struct vnode *, int); +struct mount *vfs_ref_from_vp(struct vnode *); void vfs_ref(struct mount *); void vfs_rel(struct mount *); struct mount *vfs_mount_alloc(struct vnode *, struct vfsconf *, const char *,
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