Date: Mon, 30 Jan 2012 19:35:16 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r230782 - head/sys/kern Message-ID: <201201301935.q0UJZGW7099426@svn.freebsd.org>
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Author: jhb Date: Mon Jan 30 19:35:15 2012 New Revision: 230782 URL: http://svn.freebsd.org/changeset/base/230782 Log: Refine the implementation of POSIX_FADV_NOREUSE for the read(2) case such that instead of using direct I/O it allows read-ahead similar to POSIX_FADV_NORMAL, but invokes VOP_ADVISE(POSIX_FADV_DONTNEED) after the read(2) has completed to purge just-read data. The write(2) path continues to use direct I/O for POSIX_FADV_NOREUSE for now. Note that NOREUSE works optimally if an application reads and writes full fs blocks. Modified: head/sys/kern/vfs_vnops.c Modified: head/sys/kern/vfs_vnops.c ============================================================================== --- head/sys/kern/vfs_vnops.c Mon Jan 30 19:34:41 2012 (r230781) +++ head/sys/kern/vfs_vnops.c Mon Jan 30 19:35:15 2012 (r230782) @@ -519,6 +519,7 @@ vn_read(fp, uio, active_cred, flags, td) int error, ioflag; struct mtx *mtxp; int advice, vfslocked; + off_t offset; KASSERT(uio->uio_td == td, ("uio_td %p is not td %p", uio->uio_td, td)); @@ -558,19 +559,14 @@ vn_read(fp, uio, active_cred, flags, td) switch (advice) { case POSIX_FADV_NORMAL: case POSIX_FADV_SEQUENTIAL: + case POSIX_FADV_NOREUSE: ioflag |= sequential_heuristic(uio, fp); break; case POSIX_FADV_RANDOM: /* Disable read-ahead for random I/O. */ break; - case POSIX_FADV_NOREUSE: - /* - * Request the underlying FS to discard the buffers - * and pages after the I/O is complete. - */ - ioflag |= IO_DIRECT; - break; } + offset = uio->uio_offset; #ifdef MAC error = mac_vnode_check_read(active_cred, fp->f_cred, vp); @@ -587,6 +583,10 @@ vn_read(fp, uio, active_cred, flags, td) } fp->f_nextoff = uio->uio_offset; VOP_UNLOCK(vp, 0); + if (error == 0 && advice == POSIX_FADV_NOREUSE && + offset != uio->uio_offset) + error = VOP_ADVISE(vp, offset, uio->uio_offset - 1, + POSIX_FADV_DONTNEED); VFS_UNLOCK_GIANT(vfslocked); return (error); }
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