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ovl: check if all layers are on the same fs 

Some features can only work when all layers are on the same fs.  Test this
condition during mount time, so features can check them later.

Add helper ovl_same_sb() to return the common super block in case all
layers are on the same fs.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein 2017-03-22 08:42:21 -04:00 committed by Miklos Szeredi
parent 4a99f3c83d
commit 7bcd74b98d
4 changed files with 18 additions and 0 deletions
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1
fs/overlayfs/overlayfs.h
View File

@ -151,6 +151,7 @@ int ovl_want_write(struct dentry *dentry);
void ovl_drop_write(struct dentry *dentry);
struct dentry *ovl_workdir(struct dentry *dentry);
const struct cred *ovl_override_creds(struct super_block *sb);
struct super_block *ovl_same_sb(struct super_block *sb);
struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
bool ovl_dentry_remote(struct dentry *dentry);
bool ovl_dentry_weird(struct dentry *dentry);

2
fs/overlayfs/ovl_entry.h
View File

@ -29,6 +29,8 @@ struct ovl_fs {
const struct cred *creator_cred;
bool tmpfile;
wait_queue_head_t copyup_wq;
/* sb common to all layers */
struct super_block *same_sb;
};
/* private information held for every overlayfs dentry */

8
fs/overlayfs/super.c
View File

@ -914,11 +914,19 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
ufs->lower_mnt[ufs->numlower] = mnt;
ufs->numlower++;
/* Check if all lower layers are on same sb */
if (i == 0)
ufs->same_sb = mnt->mnt_sb;
else if (ufs->same_sb != mnt->mnt_sb)
ufs->same_sb = NULL;
}
/* If the upper fs is nonexistent, we mark overlayfs r/o too */
if (!ufs->upper_mnt)
sb->s_flags |= MS_RDONLY;
else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
ufs->same_sb = NULL;
if (remote)
sb->s_d_op = &ovl_reval_dentry_operations;

7
fs/overlayfs/util.c
View File

@ -41,6 +41,13 @@ const struct cred *ovl_override_creds(struct super_block *sb)
return override_creds(ofs->creator_cred);
}
struct super_block *ovl_same_sb(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->same_sb;
}
struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
{
size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);