Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932243AbZLFH7w (ORCPT ); Sun, 6 Dec 2009 02:59:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932303AbZLFH7r (ORCPT ); Sun, 6 Dec 2009 02:59:47 -0500 Received: from mtoichi13.ns.itscom.net ([219.110.2.183]:50577 "EHLO mtoichi13.ns.itscom.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932298AbZLFH7m (ORCPT ); Sun, 6 Dec 2009 02:59:42 -0500 From: "J. R. Okajima" To: linux-kernel@vger.kernel.org Cc: stewb@linux-foundation.org, "J. R. Okajima" Subject: [RFC 1/5] vfs, support pathconf(3) with _PC_LINK_MAX Date: Sun, 6 Dec 2009 16:58:59 +0900 Message-Id: <1260086343-8406-2-git-send-email-hooanon05@yahoo.co.jp> X-Mailer: git-send-email 1.6.1.284.g5dc13 In-Reply-To: <1260086343-8406-1-git-send-email-hooanon05@yahoo.co.jp> References: <1260086343-8406-1-git-send-email-hooanon05@yahoo.co.jp> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4224 Lines: 111 The pathconf(_PC_LINK_MAX) cannot get the correct value, since linux kernel doesn't provide such interface. And the current implementation in GLibc issues statfs(2) first and then returns the predefined value (EXT2_LINK_MAX, etc) based upoin the filesystem type. But GLibc doesn't support all filesystem types. ie. when the target filesystem is unknown to pathconf(3), it will return LINUX_LINK_MAX (127). For GLibc, there is no way except implementing this poor method. This patch makes statfs(2) return the correct value via struct statfs.f_spare[0]. Signed-off-by: J. R. Okajima --- fs/compat.c | 5 +++-- fs/libfs.c | 1 + fs/open.c | 9 +++++++-- include/linux/statfs.h | 6 ++++++ 4 files changed, 17 insertions(+), 4 deletions(-) diff --git a/fs/compat.c b/fs/compat.c index 6c19040..fd1d96b 100644 --- a/fs/compat.c +++ b/fs/compat.c @@ -246,7 +246,7 @@ static int put_compat_statfs(struct compat_statfs __user *ubuf, struct kstatfs * __put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) || __put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) || __put_user(kbuf->f_frsize, &ubuf->f_frsize) || - __put_user(0, &ubuf->f_spare[0]) || + __put_user(kbuf->f_linkmax, &ubuf->f_linkmax) || /* f_spare[0] */ __put_user(0, &ubuf->f_spare[1]) || __put_user(0, &ubuf->f_spare[2]) || __put_user(0, &ubuf->f_spare[3]) || @@ -319,7 +319,8 @@ static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstat __put_user(kbuf->f_namelen, &ubuf->f_namelen) || __put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) || __put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) || - __put_user(kbuf->f_frsize, &ubuf->f_frsize)) + __put_user(kbuf->f_frsize, &ubuf->f_frsize) || + __put_user(kbuf->f_linkmax, &ubuf->f_linkmax)) /* f_spare[0] */ return -EFAULT; return 0; } diff --git a/fs/libfs.c b/fs/libfs.c index 219576c..1a078dd 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -28,6 +28,7 @@ int simple_statfs(struct dentry *dentry, struct kstatfs *buf) buf->f_type = dentry->d_sb->s_magic; buf->f_bsize = PAGE_CACHE_SIZE; buf->f_namelen = NAME_MAX; + buf->f_linkmax = LINK_MAX_UNLIMITED; /* cf. simple_link() */ return 0; } diff --git a/fs/open.c b/fs/open.c index 4f01e06..4ca513f 100644 --- a/fs/open.c +++ b/fs/open.c @@ -39,6 +39,7 @@ int vfs_statfs(struct dentry *dentry, struct kstatfs *buf) retval = -ENOSYS; if (dentry->d_sb->s_op->statfs) { memset(buf, 0, sizeof(*buf)); + buf->f_linkmax = LINK_MAX_DEFAULT; retval = security_sb_statfs(dentry); if (retval) return retval; @@ -91,7 +92,9 @@ static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf) buf->f_fsid = st.f_fsid; buf->f_namelen = st.f_namelen; buf->f_frsize = st.f_frsize; - memset(buf->f_spare, 0, sizeof(buf->f_spare)); + /* contain f_linkmax */ + BUILD_BUG_ON(sizeof(buf->f_spare) < sizeof(st.f_spare)); + memcpy(buf->f_spare, st.f_spare, sizeof(st.f_spare)); } return 0; } @@ -118,7 +121,9 @@ static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf) buf->f_fsid = st.f_fsid; buf->f_namelen = st.f_namelen; buf->f_frsize = st.f_frsize; - memset(buf->f_spare, 0, sizeof(buf->f_spare)); + /* contain f_linkmax */ + BUILD_BUG_ON(sizeof(buf->f_spare) < sizeof(st.f_spare)); + memcpy(buf->f_spare, st.f_spare, sizeof(st.f_spare)); } return 0; } diff --git a/include/linux/statfs.h b/include/linux/statfs.h index b34cc82..958b837 100644 --- a/include/linux/statfs.h +++ b/include/linux/statfs.h @@ -19,4 +19,10 @@ struct kstatfs { long f_spare[5]; }; +/* support pathconf(3) with _PC_LINK_MAX */ +#define f_linkmax f_spare[0] +#define LINK_MAX_UNLIMITED (-1) /* link(2) does not check i_nlink */ +#define LINK_MAX_UNSUPPORTED 1 /* hardlink is unavailable */ +#define LINK_MAX_DEFAULT 127 /* compatibility to glibc */ + #endif -- 1.6.1.284.g5dc13 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/