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Subject[v3][PATCH 5/5] Merge code for single and multiple-instance mounts

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Subject: [v3][PATCH 5/5] Merge code for single and multiple-instance mounts

new_pts_mount() (including the get_sb_nodev()), shares a lot of code
with init_pts_mount(). The only difference between them is the 'test-super'
function passed into sget().

Move all common code into devpts_get_sb() and remove the new_pts_mount() and
init_pts_mount() functions,

Changelog[v3]:
[Serge Hallyn]: Remove unnecessary printk()s
Changelog[v2]:
(Christoph Hellwig): Merge code in 'do_pts_mount()' into devpts_get_sb()

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Tested-by: Serge Hallyn <serue@us.ibm.com>
---
fs/devpts/inode.c | 115 ++++++++++++++++++----------------------------------
1 files changed, 40 insertions(+), 75 deletions(-)

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index c821c9a..c25fb34 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -325,87 +325,38 @@ static int compare_init_pts_sb(struct super_block *s, void *p)
}

/*
- * Mount a new (private) instance of devpts. PTYs created in this
- * instance are independent of the PTYs in other devpts instances.
- */
-static int new_pts_mount(struct file_system_type *fs_type, int flags,
- void *data, struct pts_mount_opts *opts, struct vfsmount *mnt)
-{
- int err;
- struct pts_fs_info *fsi;
-
- printk(KERN_NOTICE "devpts: newinstance mount\n");
-
- err = get_sb_nodev(fs_type, flags, data, devpts_fill_super, mnt);
- if (err)
- return err;
-
- fsi = DEVPTS_SB(mnt->mnt_sb);
- memcpy(&fsi->mount_opts, opts, sizeof(opts));
-
- return 0;
-}
-
-/*
- * init_pts_mount()
+ * devpts_get_sb()
+ *
+ * If the '-o newinstance' mount option was specified, mount a new
+ * (private) instance of devpts. PTYs created in this instance are
+ * independent of the PTYs in other devpts instances.
*
- * Mount or remount the initial kernel mount of devpts. This type of
- * mount maintains the legacy, single-instance semantics, while the
- * kernel still allows multiple-instances.
+ * If the '-o newinstance' option was not specified, mount/remount the
+ * initial kernel mount of devpts. This type of mount gives the
+ * legacy, single-instance semantics.
*
- * This interface is needed to support multiple namespace semantics in
- * devpts while preserving backward compatibility of the current 'single-
- * namespace' semantics. i.e all mounts of devpts without the 'newinstance'
- * mount option should bind to the initial kernel mount, like
- * get_sb_single().
+ * The 'newinstance' option is needed to support multiple namespace
+ * semantics in devpts while preserving backward compatibility of the
+ * current 'single-namespace' semantics. i.e all mounts of devpts
+ * without the 'newinstance' mount option should bind to the initial
+ * kernel mount, like get_sb_single().
*
- * Mounts with 'newinstance' option create a new private namespace.
+ * Mounts with 'newinstance' option create a new, private namespace.
*
- * But for single-mount semantics, devpts cannot use get_sb_single(),
+ * NOTE:
+ *
+ * For single-mount semantics, devpts cannot use get_sb_single(),
* because get_sb_single()/sget() find and use the super-block from
* the most recent mount of devpts. But that recent mount may be a
* 'newinstance' mount and get_sb_single() would pick the newinstance
* super-block instead of the initial super-block.
- *
- * This interface is identical to get_sb_single() except that it
- * consistently selects the 'single-namespace' superblock even in the
- * presence of the private namespace (i.e 'newinstance') super-blocks.
*/
-static int init_pts_mount(struct file_system_type *fs_type, int flags,
- void *data, struct pts_mount_opts *opts, struct vfsmount *mnt)
-{
- struct super_block *s;
- struct pts_fs_info *fsi;
- int error;
-
- s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
- if (IS_ERR(s))
- return PTR_ERR(s);
-
- if (!s->s_root) {
- s->s_flags = flags;
- error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
- if (error) {
- up_write(&s->s_umount);
- deactivate_super(s);
- return error;
- }
- s->s_flags |= MS_ACTIVE;
- }
-
- simple_set_mnt(mnt, s);
-
- fsi = DEVPTS_SB(mnt->mnt_sb);
- memcpy(&fsi->mount_opts, opts, sizeof(opts));
-
- return 0;
-}
-
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
int error;
struct pts_mount_opts opts;
+ struct super_block *s;

memset(&opts, 0, sizeof(opts));
if (data) {
@@ -415,23 +366,37 @@ static int devpts_get_sb(struct file_system_type *fs_type,
}

if (opts.newinstance)
- error = new_pts_mount(fs_type, flags, data, &opts, mnt);
+ s = sget(fs_type, NULL, set_anon_super, NULL);
else
- error = init_pts_mount(fs_type, flags, data, &opts, mnt);
+ s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);

- if (error)
- return error;
+ if (IS_ERR(s))
+ return PTR_ERR(s);

- error = mknod_ptmx(mnt->mnt_sb);
+ if (!s->s_root) {
+ s->s_flags = flags;
+ error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
+ if (error)
+ goto out_undo_sget;
+ s->s_flags |= MS_ACTIVE;
+ }
+
+ simple_set_mnt(mnt, s);
+
+ memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
+
+ error = mknod_ptmx(s);
if (error)
goto out_dput;

return 0;

out_dput:
- dput(mnt->mnt_sb->s_root);
- up_write(&mnt->mnt_sb->s_umount);
- deactivate_super(mnt->mnt_sb);
+ dput(s->s_root);
+
+out_undo_sget:
+ up_write(&s->s_umount);
+ deactivate_super(s);
return error;
}

--
1.5.2.5


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