Date: Mon, 24 Jul 2023 22:03:18 GMT From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 5b353925ff61 - main - vnode read(2)/write(2): acquire rangelock regardless of do_vn_io_fault() Message-ID: <202307242203.36OM3IwQ009522@gitrepo.freebsd.org>
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The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=5b353925ff61b9ddb97bb453ba75278b578ed7d9 commit 5b353925ff61b9ddb97bb453ba75278b578ed7d9 Author: Konstantin Belousov <kib@FreeBSD.org> AuthorDate: 2023-07-23 15:55:50 +0000 Commit: Konstantin Belousov <kib@FreeBSD.org> CommitDate: 2023-07-24 22:02:59 +0000 vnode read(2)/write(2): acquire rangelock regardless of do_vn_io_fault() To ensure atomicity of reads against parallel writes and truncates, vnode lock was not enough at least since introduction of vn_io_fault(). That code only take rangelock when it was possible that vn_read() and vn_write() could drop the vnode lock. At least since the introduction of VOP_READ_PGCACHE() which generally does not lock the vnode at all, rangelocks become required even for filesystems that do not need vn_io_fault() workaround. For instance, tmpfs. PR: 272678 Analyzed and reviewed by: Andrew Gierth <andrew@tao11.riddles.org.uk> Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D41158 --- sys/kern/vfs_vnops.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c index 83e95731d7c4..306840ff0357 100644 --- a/sys/kern/vfs_vnops.c +++ b/sys/kern/vfs_vnops.c @@ -1443,6 +1443,7 @@ vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred, void *rl_cookie; struct vn_io_fault_args args; int error; + bool rl_locked; doio = uio->uio_rw == UIO_READ ? vn_read : vn_write; vp = fp->f_vnode; @@ -1465,12 +1466,7 @@ vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred, } foffset_lock_uio(fp, uio, flags); - if (do_vn_io_fault(vp, uio)) { - args.kind = VN_IO_FAULT_FOP; - args.args.fop_args.fp = fp; - args.args.fop_args.doio = doio; - args.cred = active_cred; - args.flags = flags | FOF_OFFSET; + if (vp->v_type == VREG) { if (uio->uio_rw == UIO_READ) { rl_cookie = vn_rangelock_rlock(vp, uio->uio_offset, uio->uio_offset + uio->uio_resid); @@ -1482,11 +1478,22 @@ vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred, rl_cookie = vn_rangelock_wlock(vp, uio->uio_offset, uio->uio_offset + uio->uio_resid); } + rl_locked = true; + } else { + rl_locked = false; + } + if (do_vn_io_fault(vp, uio)) { + args.kind = VN_IO_FAULT_FOP; + args.args.fop_args.fp = fp; + args.args.fop_args.doio = doio; + args.cred = active_cred; + args.flags = flags | FOF_OFFSET; error = vn_io_fault1(vp, uio, &args, td); - vn_rangelock_unlock(vp, rl_cookie); } else { error = doio(fp, uio, active_cred, flags | FOF_OFFSET, td); } + if (rl_locked) + vn_rangelock_unlock(vp, rl_cookie); foffset_unlock_uio(fp, uio, flags); return (error); }
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