From: Trond Myklebust Date: Wed, 16 May 2007 16:53:28 -0400 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 --- fs/nfs/super.c | 34 +++++++++++++++++++++++++++++----- include/linux/nfs4_mount.h | 1 + include/linux/nfs_mount.h | 1 + 3 files changed, 31 insertions(+), 5 deletions(-) diff --git a/fs/nfs/super.c b/fs/nfs/super.c index ca20d3c..c03120a 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -291,6 +291,7 @@ static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss, { NFS_MOUNT_NONLM, ",nolock", "" }, { NFS_MOUNT_NOACL, ",noacl", "" }, { NFS_MOUNT_NORDIRPLUS, ",nordirplus", "" }, + { NFS_MOUNT_UNSHARED, ",nosharecache", ""}, { 0, NULL, NULL } }; const struct proc_nfs_info *nfs_infop; @@ -602,6 +603,9 @@ static int nfs_compare_super(struct super_block *sb, void *data) if (old->nfs_client != server->nfs_client) return 0; + /* Note: NFS_MOUNT_UNSHARED == NFS4_MOUNT_UNSHARED */ + if (old->flags & NFS_MOUNT_UNSHARED) + return 0; if (memcmp(&old->fsid, &server->fsid, sizeof(old->fsid)) != 0) return 0; return 1; @@ -615,6 +619,7 @@ static int nfs_get_sb(struct file_system_type *fs_type, struct nfs_fh mntfh; struct nfs_mount_data *data = raw_data; struct dentry *mntroot; + int (*compare_super)(struct super_block *,void *) = nfs_compare_super; int error; /* Validate the mount data */ @@ -629,8 +634,11 @@ static int nfs_get_sb(struct file_system_type *fs_type, goto out_err_noserver; } + if (server->flags & NFS_MOUNT_UNSHARED) + compare_super = NULL; + /* Get a superblock - note that we may end up sharing one that already exists */ - s = sget(fs_type, nfs_compare_super, nfs_set_super, server); + s = sget(fs_type, compare_super, nfs_set_super, server); if (IS_ERR(s)) { error = PTR_ERR(s); goto out_err_nosb; @@ -691,6 +699,7 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags, struct super_block *s; struct nfs_server *server; struct dentry *mntroot; + int (*compare_super)(struct super_block *,void *) = nfs_compare_super; int error; dprintk("--> nfs_xdev_get_sb()\n"); @@ -702,8 +711,11 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags, goto out_err_noserver; } + if (server->flags & NFS_MOUNT_UNSHARED) + compare_super = NULL; + /* Get a superblock - note that we may end up sharing one that already exists */ - s = sget(&nfs_fs_type, nfs_compare_super, nfs_set_super, server); + s = sget(&nfs_fs_type, compare_super, nfs_set_super, server); if (IS_ERR(s)) { error = PTR_ERR(s); goto out_err_nosb; @@ -808,6 +820,7 @@ static int nfs4_get_sb(struct file_system_type *fs_type, struct dentry *mntroot; char *mntpath = NULL, *hostname = NULL, ip_addr[16]; void *p; + int (*compare_super)(struct super_block *,void *) = nfs_compare_super; int error; if (data == NULL) { @@ -879,8 +892,11 @@ static int nfs4_get_sb(struct file_system_type *fs_type, goto out_err_noserver; } + if (server->flags & NFS4_MOUNT_UNSHARED) + compare_super = NULL; + /* Get a superblock - note that we may end up sharing one that already exists */ - s = sget(fs_type, nfs_compare_super, nfs_set_super, server); + s = sget(fs_type, compare_super, nfs_set_super, server); if (IS_ERR(s)) { error = PTR_ERR(s); goto out_free; @@ -949,6 +965,7 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags, struct super_block *s; struct nfs_server *server; struct dentry *mntroot; + int (*compare_super)(struct super_block *,void *) = nfs_compare_super; int error; dprintk("--> nfs4_xdev_get_sb()\n"); @@ -960,8 +977,11 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags, goto out_err_noserver; } + if (server->flags & NFS4_MOUNT_UNSHARED) + compare_super = NULL; + /* Get a superblock - note that we may end up sharing one that already exists */ - s = sget(&nfs_fs_type, nfs_compare_super, nfs_set_super, server); + s = sget(&nfs_fs_type, compare_super, nfs_set_super, server); if (IS_ERR(s)) { error = PTR_ERR(s); goto out_err_nosb; @@ -1016,6 +1036,7 @@ static int nfs4_referral_get_sb(struct file_system_type *fs_type, int flags, struct nfs_server *server; struct dentry *mntroot; struct nfs_fh mntfh; + int (*compare_super)(struct super_block *,void *) = nfs_compare_super; int error; dprintk("--> nfs4_referral_get_sb()\n"); @@ -1027,8 +1048,11 @@ static int nfs4_referral_get_sb(struct file_system_type *fs_type, int flags, goto out_err_noserver; } + if (server->flags & NFS4_MOUNT_UNSHARED) + compare_super = NULL; + /* Get a superblock - note that we may end up sharing one that already exists */ - s = sget(&nfs_fs_type, nfs_compare_super, nfs_set_super, server); + s = sget(&nfs_fs_type, compare_super, nfs_set_super, server); if (IS_ERR(s)) { error = PTR_ERR(s); goto out_err_nosb; diff --git a/include/linux/nfs4_mount.h b/include/linux/nfs4_mount.h index 26b4c83..ad1bd4a 100644 --- a/include/linux/nfs4_mount.h +++ b/include/linux/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 /* 1 */ #define NFS4_MOUNT_FLAGMASK 0xFFFF #endif diff --git a/include/linux/nfs_mount.h b/include/linux/nfs_mount.h index cc8b9c5..3e3b521 100644 --- a/include/linux/nfs_mount.h +++ b/include/linux/nfs_mount.h @@ -62,6 +62,7 @@ struct nfs_mount_data { #define NFS_MOUNT_STRICTLOCK 0x1000 /* reserved for NFSv4 */ #define NFS_MOUNT_SECFLAVOUR 0x2000 /* 5 */ #define NFS_MOUNT_NORDIRPLUS 0x4000 /* 5 */ +#define NFS_MOUNT_UNSHARED 0x8000 /* 5 */ #define NFS_MOUNT_FLAGMASK 0xFFFF #endif