From owner-dev-commits-src-main@freebsd.org Sun Apr 11 06:47:56 2021 Return-Path: Delivered-To: dev-commits-src-main@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 8AD8F5E2DD9; Sun, 11 Apr 2021 06:47:56 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4FJ2W03KzZz4rVv; Sun, 11 Apr 2021 06:47:56 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 65D641F8A5; Sun, 11 Apr 2021 06:47:56 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 13B6lu2E076794; Sun, 11 Apr 2021 06:47:56 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 13B6luH2076793; Sun, 11 Apr 2021 06:47:56 GMT (envelope-from git) Date: Sun, 11 Apr 2021 06:47:56 GMT Message-Id: <202104110647.13B6luH2076793@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Ka Ho Ng Subject: git: b77f5f5553e8 - main - vnode_pager_setsize.9: Some clarifications on the manpage MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: khng X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: b77f5f5553e8ac7868b4b234a36bda3cf2db0907 Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for the main branch of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 11 Apr 2021 06:47:56 -0000 The branch main has been updated by khng: URL: https://cgit.FreeBSD.org/src/commit/?id=b77f5f5553e8ac7868b4b234a36bda3cf2db0907 commit b77f5f5553e8ac7868b4b234a36bda3cf2db0907 Author: Ka Ho Ng AuthorDate: 2021-04-11 06:45:37 +0000 Commit: Ka Ho Ng CommitDate: 2021-04-11 06:47:40 +0000 vnode_pager_setsize.9: Some clarifications on the manpage A number of changes: - Clarifies the locking rules when calling the routine. - Correct the description regarding the content range to be purged. - Document the effects on page fault handler. MFC after: 3 days MFC with: 86a52e262a6f Sponsored by: The FreeBSD Foundation Reviewed by: bcr, kib Approved by: philip (mentor) Differential Revision: https://reviews.freebsd.org/D29637 --- share/man/man9/vnode_pager_setsize.9 | 41 ++++++++++++++++++++---------------- 1 file changed, 23 insertions(+), 18 deletions(-) diff --git a/share/man/man9/vnode_pager_setsize.9 b/share/man/man9/vnode_pager_setsize.9 index c59a01796f20..0dc3b2057930 100644 --- a/share/man/man9/vnode_pager_setsize.9 +++ b/share/man/man9/vnode_pager_setsize.9 @@ -27,7 +27,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd April 6, 2021 +.Dd April 8, 2021 .Dt VNODE_PAGER_SETSIZE 9 .Os .Sh NAME @@ -41,26 +41,31 @@ .Fn vnode_pager_setsize "struct vnode *vp" "vm_ooffset_t nsize" .Sh DESCRIPTION .Nm -lets the VM system know about a change in size for a file. -Content beyond the new EOF specified by the -.Fa nsize -argument will be purged from the cache. -This function is useful for use within file system code to implement -truncation in -.Xr VOP_SETATTR 9 . -.Sh IMPLEMENTATION NOTES +lets the VM system know about a change in size for a file, +and updates the object size and vnode pager size of the vm object in +.Fa vp +with +.Fa nsize . +Page faults on the object mapping with offset beyond the new object +size results in +.Va SIGBUS . +.Pp +Pages between the old EOF and the new EOF are removed from the object queue +if the file size shrinks. In case the new EOF specified by the .Fa nsize -argument is not aligned to page boundaries, -partial-page area starting beyond the EOF will be zeroed. -In partial-page area, -for content occupying whole blocks within block -boundaries, -the dirty bits for the corresponding blocks will be cleared. -.Sh LOCKING -Writer lock of the VM object of +argument is not aligned to page boundary, +partial-page area starting beyond the EOF is zeroed and marked invalid. +if the page exists resident. +.Pp +In case the vnode .Fa vp -will be held within the function. +does not have a VM object allocated, the effect of calling this function is no-op. +.Pp +This function must be used within file system code to implement truncation +if the file system allocates vm objects for vnodes. +.Sh LOCKS +The vnode should be exclusively locked on entry and will still be locked on exit. .Sh SEE ALSO .Xr vnode 9 .Sh HISTORY