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NFS: Fix the mount regression
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This avoids the recent NFS mount regression (returning EBUSY when
mounting the same filesystem twice with different parameters).

The best I can do given the constraints appears to be to have the kernel
first look for a superblock that matches both the fsid and the
user-specified mount options, and then spawn off a new superblock if
that search fails.

Note that this is not the same as specifying nosharecache everywhere
since nosharecache will never attempt to match an existing superblock.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: Hua Zhong <hzhong@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Trond Myklebust authored and Linus Torvalds committed Sep 1, 2007
1 parent 36ad488 commit e89a5a4
Showing 1 changed file with 64 additions and 46 deletions.
110 changes: 64 additions & 46 deletions fs/nfs/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1303,34 +1303,6 @@ static void nfs_clone_super(struct super_block *sb,
nfs_initialise_sb(sb);
}

static int nfs_set_super(struct super_block *s, void *_server)
{
struct nfs_server *server = _server;
int ret;

s->s_fs_info = server;
ret = set_anon_super(s, server);
if (ret == 0)
server->s_dev = s->s_dev;
return ret;
}

static int nfs_compare_super(struct super_block *sb, void *data)
{
struct nfs_server *server = data, *old = NFS_SB(sb);

if (memcmp(&old->nfs_client->cl_addr,
&server->nfs_client->cl_addr,
sizeof(old->nfs_client->cl_addr)) != 0)
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;
}

#define NFS_MS_MASK (MS_RDONLY|MS_NOSUID|MS_NODEV|MS_NOEXEC|MS_SYNCHRONOUS)

static int nfs_compare_mount_options(const struct super_block *s, const struct nfs_server *b, int flags)
Expand Down Expand Up @@ -1359,9 +1331,46 @@ static int nfs_compare_mount_options(const struct super_block *s, const struct n
goto Ebusy;
if (clnt_a->cl_auth->au_flavor != clnt_b->cl_auth->au_flavor)
goto Ebusy;
return 0;
return 1;
Ebusy:
return -EBUSY;
return 0;
}

struct nfs_sb_mountdata {
struct nfs_server *server;
int mntflags;
};

static int nfs_set_super(struct super_block *s, void *data)
{
struct nfs_sb_mountdata *sb_mntdata = data;
struct nfs_server *server = sb_mntdata->server;
int ret;

s->s_flags = sb_mntdata->mntflags;
s->s_fs_info = server;
ret = set_anon_super(s, server);
if (ret == 0)
server->s_dev = s->s_dev;
return ret;
}

static int nfs_compare_super(struct super_block *sb, void *data)
{
struct nfs_sb_mountdata *sb_mntdata = data;
struct nfs_server *server = sb_mntdata->server, *old = NFS_SB(sb);
int mntflags = sb_mntdata->mntflags;

if (memcmp(&old->nfs_client->cl_addr,
&server->nfs_client->cl_addr,
sizeof(old->nfs_client->cl_addr)) != 0)
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 nfs_compare_mount_options(sb, server, mntflags);
}

static int nfs_get_sb(struct file_system_type *fs_type,
Expand All @@ -1373,6 +1382,9 @@ static int nfs_get_sb(struct file_system_type *fs_type,
struct nfs_mount_data *data = raw_data;
struct dentry *mntroot;
int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
struct nfs_sb_mountdata sb_mntdata = {
.mntflags = flags,
};
int error;

/* Validate the mount data */
Expand All @@ -1386,28 +1398,25 @@ static int nfs_get_sb(struct file_system_type *fs_type,
error = PTR_ERR(server);
goto out;
}
sb_mntdata.server = server;

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, compare_super, nfs_set_super, server);
s = sget(fs_type, compare_super, nfs_set_super, &sb_mntdata);
if (IS_ERR(s)) {
error = PTR_ERR(s);
goto out_err_nosb;
}

if (s->s_fs_info != server) {
error = nfs_compare_mount_options(s, server, flags);
nfs_free_server(server);
server = NULL;
if (error < 0)
goto error_splat_super;
}

if (!s->s_root) {
/* initial superblock/root creation */
s->s_flags = flags;
nfs_fill_super(s, data);
}

Expand Down Expand Up @@ -1460,6 +1469,9 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags,
struct nfs_server *server;
struct dentry *mntroot;
int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
struct nfs_sb_mountdata sb_mntdata = {
.mntflags = flags,
};
int error;

dprintk("--> nfs_xdev_get_sb()\n");
Expand All @@ -1470,28 +1482,25 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags,
error = PTR_ERR(server);
goto out_err_noserver;
}
sb_mntdata.server = server;

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, compare_super, nfs_set_super, server);
s = sget(&nfs_fs_type, compare_super, nfs_set_super, &sb_mntdata);
if (IS_ERR(s)) {
error = PTR_ERR(s);
goto out_err_nosb;
}

if (s->s_fs_info != server) {
error = nfs_compare_mount_options(s, server, flags);
nfs_free_server(server);
server = NULL;
if (error < 0)
goto error_splat_super;
}

if (!s->s_root) {
/* initial superblock/root creation */
s->s_flags = flags;
nfs_clone_super(s, data->sb);
}

Expand Down Expand Up @@ -1729,6 +1738,9 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
struct dentry *mntroot;
char *mntpath = NULL, *hostname = NULL, *ip_addr = NULL;
int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
struct nfs_sb_mountdata sb_mntdata = {
.mntflags = flags,
};
int error;

/* Validate the mount data */
Expand All @@ -1744,12 +1756,13 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
error = PTR_ERR(server);
goto out;
}
sb_mntdata.server = server;

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, compare_super, nfs_set_super, server);
s = sget(fs_type, compare_super, nfs_set_super, &sb_mntdata);
if (IS_ERR(s)) {
error = PTR_ERR(s);
goto out_free;
Expand All @@ -1762,7 +1775,6 @@ static int nfs4_get_sb(struct file_system_type *fs_type,

if (!s->s_root) {
/* initial superblock/root creation */
s->s_flags = flags;
nfs4_fill_super(s);
}

Expand Down Expand Up @@ -1816,6 +1828,9 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags,
struct nfs_server *server;
struct dentry *mntroot;
int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
struct nfs_sb_mountdata sb_mntdata = {
.mntflags = flags,
};
int error;

dprintk("--> nfs4_xdev_get_sb()\n");
Expand All @@ -1826,12 +1841,13 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags,
error = PTR_ERR(server);
goto out_err_noserver;
}
sb_mntdata.server = server;

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, compare_super, nfs_set_super, server);
s = sget(&nfs_fs_type, compare_super, nfs_set_super, &sb_mntdata);
if (IS_ERR(s)) {
error = PTR_ERR(s);
goto out_err_nosb;
Expand All @@ -1844,7 +1860,6 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags,

if (!s->s_root) {
/* initial superblock/root creation */
s->s_flags = flags;
nfs4_clone_super(s, data->sb);
}

Expand Down Expand Up @@ -1887,6 +1902,9 @@ static int nfs4_referral_get_sb(struct file_system_type *fs_type, int flags,
struct dentry *mntroot;
struct nfs_fh mntfh;
int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
struct nfs_sb_mountdata sb_mntdata = {
.mntflags = flags,
};
int error;

dprintk("--> nfs4_referral_get_sb()\n");
Expand All @@ -1897,12 +1915,13 @@ static int nfs4_referral_get_sb(struct file_system_type *fs_type, int flags,
error = PTR_ERR(server);
goto out_err_noserver;
}
sb_mntdata.server = server;

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, compare_super, nfs_set_super, server);
s = sget(&nfs_fs_type, compare_super, nfs_set_super, &sb_mntdata);
if (IS_ERR(s)) {
error = PTR_ERR(s);
goto out_err_nosb;
Expand All @@ -1915,7 +1934,6 @@ static int nfs4_referral_get_sb(struct file_system_type *fs_type, int flags,

if (!s->s_root) {
/* initial superblock/root creation */
s->s_flags = flags;
nfs4_fill_super(s);
}

Expand Down

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