From 3ecc5650e25fbcfe6d1b885b69c00d515cd485ce Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Tue, 10 Jul 2007 10:03:22 +1000 Subject: [PATCH] mount.nfs: Add the mount option "nosharecache" Prior to David Howell's mount changes in 2.6.18, users who mounted different directories which happened to be from the same filesystem on the server would get different super blocks, and hence could choose different mount options. As long as there were no hard linked files that crossed from one subtree to another, this was quite safe. Post the changes, if the two directories are on the same filesystem (have the same 'fsid'), they will share the same super block, and hence the same mount options. Add a flag to allow users to elect not to share the NFS super block with another mount point, even if the fsids are the same. This will allow users to set different mount options for the two different super blocks, as was previously possible. It is still up to the user to ensure that there are no cache coherency issues when doing this, however the default behaviour will be to share super blocks whenever two paths result in the same fsid. Signed-off-by: Trond Myklebust Signed-off-by: Neil Brown --- utils/mount/nfs.man | 34 ++++++++++++++++++++++++++++++++++ utils/mount/nfs4_mount.h | 1 + utils/mount/nfs4mount.c | 14 ++++++++++---- utils/mount/nfs_mount.h | 1 + utils/mount/nfsmount.c | 4 ++++ 5 files changed, 50 insertions(+), 4 deletions(-) diff --git a/utils/mount/nfs.man b/utils/mount/nfs.man index 673556c..e66daba 100644 --- a/utils/mount/nfs.man +++ b/utils/mount/nfs.man @@ -288,6 +288,23 @@ Mount the NFS filesystem using the UDP protocol. Disables NFSv3 READDIRPLUS RPCs. Use this option when mounting servers that don't support or have broken READDIRPLUS implementations. +.TP 1.5i +.I nosharecache +As of kernel 2.6.18, it is no longer possible to mount the same +same filesystem with different mount options to a new mountpoint. +It was deemed unsafe to do so, since cached data cannot be shared +between the two mountpoints. In consequence, files or directories +that were common to both mountpoint subtrees could often be seen to +be out of sync following an update. +.br +This option allows administrators to select the pre-2.6.18 behaviour, +permitting the same filesystem to be mounted with different mount +options. +.br +.B Beware: +Use of this option is not recommended unless you are certain that there +are no hard links or subtrees of this mountpoint that are mounted +elsewhere. .P All of the non-value options have corresponding nooption forms. For example, nointr means don't allow file operations to be @@ -444,6 +461,23 @@ This extracts a server performance penalty but it allows two different NFS clients to get reasonable good results when both clients are actively writing to common filesystem on the server. +.TP 1.5i +.I nosharecache +As of kernel 2.6.18, it is no longer possible to mount the same +same filesystem with different mount options to a new mountpoint. +It was deemed unsafe to do so, since cached data cannot be shared +between the two mountpoints. In consequence, files or directories +that were common to both mountpoint subtrees could often be seen to +be out of sync following an update. +.br +This option allows administrators to select the pre-2.6.18 behaviour, +permitting the same filesystem to be mounted with different mount +options. +.br +.B Beware: +Use of this option is not recommended unless you are certain that there +are no hard links or subtrees of this mountpoint that are mounted +elsewhere. .P All of the non-value options have corresponding nooption forms. For example, nointr means don't allow file operations to be diff --git a/utils/mount/nfs4_mount.h b/utils/mount/nfs4_mount.h index 74c9b95..2fcca6d 100644 --- a/utils/mount/nfs4_mount.h +++ b/utils/mount/nfs4_mount.h @@ -65,6 +65,7 @@ struct nfs4_mount_data { #define NFS4_MOUNT_NOCTO 0x0010 /* 1 */ #define NFS4_MOUNT_NOAC 0x0020 /* 1 */ #define NFS4_MOUNT_STRICTLOCK 0x1000 /* 1 */ +#define NFS4_MOUNT_UNSHARED 0x8000 /* 5 */ #define NFS4_MOUNT_FLAGMASK 0xFFFF /* pseudoflavors: */ diff --git a/utils/mount/nfs4mount.c b/utils/mount/nfs4mount.c index 2a58d0a..0376f32 100644 --- a/utils/mount/nfs4mount.c +++ b/utils/mount/nfs4mount.c @@ -201,7 +201,7 @@ int nfs4mount(const char *spec, const char *node, int *flags, char *s; int val; int bg, soft, intr; - int nocto, noac; + int nocto, noac, unshared; int retry; int retval; time_t timeout, t; @@ -252,6 +252,7 @@ int nfs4mount(const char *spec, const char *node, int *flags, intr = NFS4_MOUNT_INTR; nocto = 0; noac = 0; + unshared = 0; retry = 10000; /* 10000 minutes ~ 1 week */ /* @@ -336,6 +337,8 @@ int nfs4mount(const char *spec, const char *node, int *flags, nocto = !val; else if (!strcmp(opt, "ac")) noac = !val; + else if (!strcmp(opt, "sharecache")) + unshared = !val; else if (!sloppy) { printf(_("unknown nfs mount option: " "%s%s\n"), val ? "" : "no", opt); @@ -347,7 +350,8 @@ int nfs4mount(const char *spec, const char *node, int *flags, data.flags = (soft ? NFS4_MOUNT_SOFT : 0) | (intr ? NFS4_MOUNT_INTR : 0) | (nocto ? NFS4_MOUNT_NOCTO : 0) - | (noac ? NFS4_MOUNT_NOAC : 0); + | (noac ? NFS4_MOUNT_NOAC : 0) + | (unshared ? NFS4_MOUNT_UNSHARED : 0); /* * Give a warning if the rpc.idmapd daemon is not running @@ -388,11 +392,13 @@ int nfs4mount(const char *spec, const char *node, int *flags, data.acregmin, data.acregmax, data.acdirmin, data.acdirmax); printf("port = %d, bg = %d, retry = %d, flags = %.8x\n", ntohs(server_addr.sin_port), bg, retry, data.flags); - printf("soft = %d, intr = %d, nocto = %d, noac = %d\n", + printf("soft = %d, intr = %d, nocto = %d, noac = %d, " + "nosharecache = %d\n", (data.flags & NFS4_MOUNT_SOFT) != 0, (data.flags & NFS4_MOUNT_INTR) != 0, (data.flags & NFS4_MOUNT_NOCTO) != 0, - (data.flags & NFS4_MOUNT_NOAC) != 0); + (data.flags & NFS4_MOUNT_NOAC) != 0, + (data.flags & NFS4_MOUNT_UNSHARED) != 0); if (num_flavour > 0) { int pf_cnt, i; diff --git a/utils/mount/nfs_mount.h b/utils/mount/nfs_mount.h index 4a061d8..50ce2a8 100644 --- a/utils/mount/nfs_mount.h +++ b/utils/mount/nfs_mount.h @@ -64,6 +64,7 @@ struct nfs_mount_data { #define NFS_MOUNT_NOACL 0x0800 /* 4 */ #define NFS_MOUNT_SECFLAVOUR 0x2000 /* 5 */ #define NFS_MOUNT_NORDIRPLUS 0x4000 /* 5 */ +#define NFS_MOUNT_UNSHARED 0x8000 /* 5 */ /* security pseudoflavors */ diff --git a/utils/mount/nfsmount.c b/utils/mount/nfsmount.c index 815064a..f21aaff 100644 --- a/utils/mount/nfsmount.c +++ b/utils/mount/nfsmount.c @@ -804,6 +804,10 @@ parse_options(char *old_opts, struct nfs_mount_data *data, data->flags &= ~NFS_MOUNT_NORDIRPLUS; if (!val) data->flags |= NFS_MOUNT_NORDIRPLUS; + } else if (!strcmp(opt, "sharecache")) { + data->flags &= ~NFS_MOUNT_UNSHARED; + if (!val) + data->flags |= NFS_MOUNT_UNSHARED; #endif } else { bad_option: -- 2.39.2