diff options
Diffstat (limited to 'fs/super.c')
| -rw-r--r-- | fs/super.c | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/fs/super.c b/fs/super.c index 96bec768684a..e04a403dbffd 100644 --- a/fs/super.c +++ b/fs/super.c @@ -546,17 +546,31 @@ bool mount_capable(struct fs_context *fc) * @test: Comparison callback * @set: Setup callback * - * Find or create a superblock using the parameters stored in the filesystem - * context and the two callback functions. + * Create a new superblock or find an existing one. * - * If an extant superblock is matched, then that will be returned with an - * elevated reference count that the caller must transfer or discard. + * The @test callback is used to find a matching existing superblock. + * Whether or not the requested parameters in @fc are taken into account + * is specific to the @test callback that is used. They may even be + * completely ignored. + * + * If an extant superblock is matched, it will be returned unless: + * + * (1) the namespace the filesystem context @fc and the extant + * superblock's namespace differ + * + * (2) the filesystem context @fc has requested that reusing an extant + * superblock is not allowed + * + * In both cases EBUSY will be returned. * * If no match is made, a new superblock will be allocated and basic - * initialisation will be performed (s_type, s_fs_info and s_id will be set and - * the set() callback will be invoked), the superblock will be published and it - * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE - * as yet unset. + * initialisation will be performed (s_type, s_fs_info and s_id will be + * set and the @set callback will be invoked), the superblock will be + * published and it will be returned in a partially constructed state + * with SB_BORN and SB_ACTIVE as yet unset. + * + * Return: On success, an extant or newly created superblock is + * returned. On failure an error pointer is returned. */ struct super_block *sget_fc(struct fs_context *fc, int (*test)(struct super_block *, struct fs_context *), @@ -603,9 +617,13 @@ retry: return s; share_extant_sb: - if (user_ns != old->s_user_ns) { + if (user_ns != old->s_user_ns || fc->exclusive) { spin_unlock(&sb_lock); destroy_unused_super(s); + if (fc->exclusive) + warnfc(fc, "reusing existing filesystem not allowed"); + else + warnfc(fc, "reusing existing filesystem in another namespace not allowed"); return ERR_PTR(-EBUSY); } if (!grab_super(old)) |