[PATCH 33/38] afs: Use fs_context to pass parameters over automount [ver #10]

David Howells
2018-07-27T17:35:09Z

Alter the AFS automounting code to create and modify an fs_context struct
when parameterising a new mount triggered by an AFS mountpoint rather than
constructing device name and option strings.

Also remove the cell=, vol= and rwpath options as they are then redundant.
The reason they existed is because the 'device name' may be derived
literally from a mountpoint object in the filesystem, so default cell and
parent-type information needed to be passed in by some other method from
the automount routines. The vol= option didn't end up being used.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Eric W. Biederman <ebiederm@redhat.com>
---

fs/afs/internal.h | 1
fs/afs/mntpt.c | 148 +++++++++++++++++++++++++++--------------------------
fs/afs/super.c | 44 +---------------
3 files changed, 78 insertions(+), 115 deletions(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index d54aab35a1ca..e35d59761d47 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -35,7 +35,6 @@ struct pagevec;
struct afs_call;

struct afs_fs_context {
- bool rwpath; /* T if the parent should be considered R/W */
bool force; /* T to force cell type */
bool autocell; /* T if set auto mount operation */
bool dyn_root; /* T if dynamic root */
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index c45aa1776591..c8a7f05b9f12 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -47,6 +47,8 @@ static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);

static unsigned long afs_mntpt_expiry_timeout = 10 * 60;

+static const char afs_root_volume[] = "root.cell";
+
/*
* no valid lookup procedure on this sort of dir
*/
@@ -68,107 +70,107 @@ static int afs_mntpt_open(struct inode *inode, struct file *file)
}

/*
- * create a vfsmount to be automounted
+ * Set the parameters for the proposed superblock.
*/
-static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
+static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
{
- struct afs_super_info *as;
- struct vfsmount *mnt;
- struct afs_vnode *vnode;
- struct page *page;
- char *devname, *options;
- bool rwpath = false;
+ struct afs_fs_context *ctx = fc->fs_private;
+ struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
+ struct afs_cell *cell;
+ const char *p;
int ret;

- _enter("{%pd}", mntpt);
-
- BUG_ON(!d_inode(mntpt));
-
- ret = -ENOMEM;
- devname = (char *) get_zeroed_page(GFP_KERNEL);
- if (!devname)
- goto error_no_devname;
-
- options = (char *) get_zeroed_page(GFP_KERNEL);
- if (!options)
- goto error_no_options;
-
- vnode = AFS_FS_I(d_inode(mntpt));
if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
/* if the directory is a pseudo directory, use the d_name */
- static const char afs_root_cell[] = ":root.cell.";
unsigned size = mntpt->d_name.len;

- ret = -ENOENT;
- if (size < 2 || size > AFS_MAXCELLNAME)
- goto error_no_page;
+ if (size < 2)
+ return -ENOENT;

+ p = mntpt->d_name.name;
if (mntpt->d_name.name[0] == '.') {
- devname[0] = '%';
- memcpy(devname + 1, mntpt->d_name.name + 1, size - 1);
- memcpy(devname + size, afs_root_cell,
- sizeof(afs_root_cell));
- rwpath = true;
- } else {
- devname[0] = '#';
- memcpy(devname + 1, mntpt->d_name.name, size);
- memcpy(devname + size + 1, afs_root_cell,
- sizeof(afs_root_cell));
+ size--;
+ p++;
+ ctx->type = AFSVL_RWVOL;
+ ctx->force = true;
+ }
+ if (size > AFS_MAXCELLNAME)
+ return -ENAMETOOLONG;
+
+ cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
+ if (IS_ERR(cell)) {
+ pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
+ return PTR_ERR(cell);
}
+ afs_put_cell(ctx->net, ctx->cell);
+ ctx->cell = cell;
+
+ ctx->volname = afs_root_volume;
+ ctx->volnamesz = sizeof(afs_root_volume) - 1;
} else {
/* read the contents of the AFS special symlink */
+ struct page *page;
loff_t size = i_size_read(d_inode(mntpt));
char *buf;

- ret = -EINVAL;
if (size > PAGE_SIZE - 1)
- goto error_no_page;
+ return -EINVAL;

page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
- if (IS_ERR(page)) {
- ret = PTR_ERR(page);
- goto error_no_page;
- }
+ if (IS_ERR(page))
+ return PTR_ERR(page);

- ret = -EIO;
- if (PageError(page))
- goto error;
+ if (PageError(page)) {
+ put_page(page);
+ return -EIO;
+ }

- buf = kmap_atomic(page);
- memcpy(devname, buf, size);
- kunmap_atomic(buf);
+ buf = kmap(page);
+ ret = vfs_parse_fs_string(fc, "source", buf, size);
+ kunmap(page);
put_page(page);
- page = NULL;
+ if (ret < 0)
+ return ret;
}

- /* work out what options we want */
- as = AFS_FS_S(mntpt->d_sb);
- if (as->cell) {
- memcpy(options, "cell=", 5);
- strcpy(options + 5, as->cell->name);
- if ((as->volume && as->volume->type == AFSVL_RWVOL) || rwpath)
- strcat(options, ",rwpath");
- }
+ return 0;
+}

- /* try and do the mount */
- _debug("--- attempting mount %s -o %s ---", devname, options);
- mnt = vfs_submount(mntpt, &afs_fs_type, devname,
- options, strlen(options) + 1);
- _debug("--- mount result %p ---", mnt);
+/*
+ * create a vfsmount to be automounted
+ */
+static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
+{
+ struct fs_context *fc;
+ struct vfsmount *mnt;
+ int ret;
+
+ BUG_ON(!d_inode(mntpt));
+
+ fc = vfs_new_fs_context(&afs_fs_type, mntpt, 0,
+ FS_CONTEXT_FOR_SUBMOUNT);
+ if (IS_ERR(fc))
+ return ERR_CAST(fc);
+
+ ret = afs_mntpt_set_params(fc, mntpt);
+ if (ret < 0)
+ goto error_fc;
+
+ ret = vfs_get_tree(fc);
+ if (ret < 0)
+ goto error_fc;
+
+ mnt = vfs_create_mount(fc, 0);
+ if (IS_ERR(mnt)) {
+ ret = PTR_ERR(mnt);
+ goto error_fc;
+ }

- free_page((unsigned long) devname);
- free_page((unsigned long) options);
- _leave(" = %p", mnt);
+ put_fs_context(fc);
return mnt;

-error:
- put_page(page);
-error_no_page:
- free_page((unsigned long) options);
-error_no_options:
- free_page((unsigned long) devname);
-error_no_devname:
- _leave(" = %d", ret);
+error_fc:
+ put_fs_context(fc);
return ERR_PTR(ret);
}

diff --git a/fs/afs/super.c b/fs/afs/super.c
index 303dc50ebbbd..55f11477ade6 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -66,30 +66,21 @@ static atomic_t afs_count_active_inodes;

enum afs_param {
Opt_autocell,
- Opt_cell,
Opt_dyn,
- Opt_rwpath,
Opt_source,
- Opt_vol,
nr__afs_params
};

static const struct fs_parameter_spec afs_param_specs[nr__afs_params] = {
[Opt_autocell] = { fs_param_takes_no_value },
- [Opt_cell] = { fs_param_is_string },
[Opt_dyn] = { fs_param_takes_no_value },
- [Opt_rwpath] = { fs_param_takes_no_value },
[Opt_source] = { fs_param_is_string },
- [Opt_vol] = { fs_param_is_string },
};

static const struct constant_table afs_param_keys[] = {
{ "autocell", Opt_autocell },
- { "cell", Opt_cell },
{ "dyn", Opt_dyn },
- { "rwpath", Opt_rwpath },
{ "source", Opt_source },
- { "vol", Opt_vol },
};

static const struct fs_parameter_description afs_fs_parameters = {
@@ -214,8 +205,8 @@ static int afs_show_options(struct seq_file *m, struct dentry *root)
*
* This can be one of the following:
* "%[cell:]volume[.]" R/W volume
- * "#[cell:]volume[.]" R/O or R/W volume (rwpath=0),
- * or R/W (rwpath=1) volume
+ * "#[cell:]volume[.]" R/O or R/W volume (R/O parent),
+ * or R/W (R/W parent) volume
* "%[cell:]volume.readonly" R/O volume
* "#[cell:]volume.readonly" R/O volume
* "%[cell:]volume.backup" Backup volume
@@ -246,9 +237,7 @@ static int afs_parse_source(struct fs_context *fc, struct fs_parameter *param)
}

/* determine the type of volume we're looking for */
- ctx->type = AFSVL_ROVOL;
- ctx->force = false;
- if (ctx->rwpath || name[0] == '%') {
+ if (name[0] == '%') {
ctx->type = AFSVL_RWVOL;
ctx->force = true;
}
@@ -317,7 +306,6 @@ static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct fs_parse_result result;
struct afs_fs_context *ctx = fc->fs_private;
- struct afs_cell *cell;
int ret;

ret = fs_parse(fc, &afs_fs_parameters, param, &result);
@@ -325,21 +313,6 @@ static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param)
return ret;

switch (result.key) {
- case Opt_cell:
- if (param->size <= 0)
- return -EINVAL;
- if (param->size > AFS_MAXCELLNAME)
- return -ENAMETOOLONG;
-
- rcu_read_lock();
- cell = afs_lookup_cell_rcu(ctx->net, param->string, param->size);
- rcu_read_unlock();
- if (IS_ERR(cell))
- return PTR_ERR(cell);
- afs_put_cell(ctx->net, ctx->cell);
- ctx->cell = cell;
- break;
-
case Opt_source:
return afs_parse_source(fc, param);

@@ -351,14 +324,6 @@ static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param)
ctx->dyn_root = true;
break;

- case Opt_rwpath:
- ctx->rwpath = true;
- break;
-
- case Opt_vol:
- return invalf(fc, "'vol' param is obsolete");
- break;
-
default:
return -EINVAL;
}
@@ -628,9 +593,6 @@ static int afs_init_fs_context(struct fs_context *fc, struct dentry *reference)
struct afs_super_info *src_as;
struct afs_cell *cell;

- if (current->nsproxy->net_ns != &init_net)
- return -EINVAL;
-
ctx = kzalloc(sizeof(struct afs_fs_context), GFP_KERNEL);
if (!ctx)
return -ENOMEM;