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-rw-r--r--Documentation/filesystems/overlayfs.rst19
-rw-r--r--fs/overlayfs/copy_up.c12
-rw-r--r--fs/overlayfs/file.c10
-rw-r--r--fs/overlayfs/ovl_entry.h6
-rw-r--r--fs/overlayfs/readdir.c3
-rw-r--r--fs/overlayfs/super.c74
6 files changed, 116 insertions, 8 deletions
diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst
index 8ea83a51c266..580ab9a0fe31 100644
--- a/Documentation/filesystems/overlayfs.rst
+++ b/Documentation/filesystems/overlayfs.rst
@@ -564,6 +564,25 @@ Note: the mount options index=off,nfs_export=on are conflicting for a
read-write mount and will result in an error.
+Volatile mount
+--------------
+
+This is enabled with the "volatile" mount option. Volatile mounts are not
+guaranteed to survive a crash. It is strongly recommended that volatile
+mounts are only used if data written to the overlay can be recreated
+without significant effort.
+
+The advantage of mounting with the "volatile" option is that all forms of
+sync calls to the upper filesystem are omitted.
+
+When overlay is mounted with "volatile" option, the directory
+"$workdir/work/incompat/volatile" is created. During next mount, overlay
+checks for this directory and refuses to mount if present. This is a strong
+indicator that user should throw away upper and work directories and create
+fresh one. In very limited cases where the user knows that the system has
+not crashed and contents of upperdir are intact, The "volatile" directory
+can be removed.
+
Testsuite
---------
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index d07fb92b7253..9d17e42d184b 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -128,7 +128,8 @@ out:
return error;
}
-static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
+static int ovl_copy_up_data(struct ovl_fs *ofs, struct path *old,
+ struct path *new, loff_t len)
{
struct file *old_file;
struct file *new_file;
@@ -218,7 +219,7 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
len -= bytes;
}
out:
- if (!error)
+ if (!error && ovl_should_sync(ofs))
error = vfs_fsync(new_file, 0);
fput(new_file);
out_fput:
@@ -484,6 +485,7 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c)
static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
{
+ struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
int err;
/*
@@ -499,7 +501,8 @@ static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
upperpath.dentry = temp;
ovl_path_lowerdata(c->dentry, &datapath);
- err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);
+ err = ovl_copy_up_data(ofs, &datapath, &upperpath,
+ c->stat.size);
if (err)
return err;
}
@@ -784,6 +787,7 @@ static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
/* Copy up data of an inode which was copied up metadata only in the past. */
static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
{
+ struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
struct path upperpath, datapath;
int err;
char *capability = NULL;
@@ -804,7 +808,7 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
goto out;
}
- err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);
+ err = ovl_copy_up_data(ofs, &datapath, &upperpath, c->stat.size);
if (err)
goto out_free;
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 0d940e29d62b..3582c3ae819c 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -331,6 +331,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
struct fd real;
const struct cred *old_cred;
ssize_t ret;
+ int ifl = iocb->ki_flags;
if (!iov_iter_count(iter))
return 0;
@@ -346,11 +347,14 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
if (ret)
goto out_unlock;
+ if (!ovl_should_sync(OVL_FS(inode->i_sb)))
+ ifl &= ~(IOCB_DSYNC | IOCB_SYNC);
+
old_cred = ovl_override_creds(file_inode(file)->i_sb);
if (is_sync_kiocb(iocb)) {
file_start_write(real.file);
ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
- ovl_iocb_to_rwf(iocb->ki_flags));
+ ovl_iocb_to_rwf(ifl));
file_end_write(real.file);
/* Update size */
ovl_copyattr(ovl_inode_real(inode), inode);
@@ -370,6 +374,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
real.flags = 0;
aio_req->orig_iocb = iocb;
kiocb_clone(&aio_req->iocb, iocb, real.file);
+ aio_req->iocb.ki_flags = ifl;
aio_req->iocb.ki_complete = ovl_aio_rw_complete;
ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
if (ret != -EIOCBQUEUED)
@@ -433,6 +438,9 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
const struct cred *old_cred;
int ret;
+ if (!ovl_should_sync(OVL_FS(file_inode(file)->i_sb)))
+ return 0;
+
ret = ovl_real_fdget_meta(file, &real, !datasync);
if (ret)
return ret;
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index b429c80879ee..1b5a2094df8e 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -17,6 +17,7 @@ struct ovl_config {
bool nfs_export;
int xino;
bool metacopy;
+ bool ovl_volatile;
};
struct ovl_sb {
@@ -90,6 +91,11 @@ static inline struct ovl_fs *OVL_FS(struct super_block *sb)
return (struct ovl_fs *)sb->s_fs_info;
}
+static inline bool ovl_should_sync(struct ovl_fs *ofs)
+{
+ return !ofs->config.ovl_volatile;
+}
+
/* private information held for every overlayfs dentry */
struct ovl_entry {
union {
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 9b0078aabaf9..f8cc15533afa 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -863,6 +863,9 @@ static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
if (!OVL_TYPE_UPPER(ovl_path_type(dentry)))
return 0;
+ if (!ovl_should_sync(OVL_FS(dentry->d_sb)))
+ return 0;
+
/*
* Need to check if we started out being a lower dir, but got copied up
*/
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f82defec02c1..8b419ef78502 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -264,6 +264,8 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
if (!ovl_upper_mnt(ofs))
return 0;
+ if (!ovl_should_sync(ofs))
+ return 0;
/*
* Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
* All the super blocks will be iterated, including upper_sb.
@@ -362,6 +364,8 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
if (ofs->config.metacopy != ovl_metacopy_def)
seq_printf(m, ",metacopy=%s",
ofs->config.metacopy ? "on" : "off");
+ if (ofs->config.ovl_volatile)
+ seq_puts(m, ",volatile");
return 0;
}
@@ -376,9 +380,11 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
if (*flags & SB_RDONLY && !sb_rdonly(sb)) {
upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
- down_read(&upper_sb->s_umount);
- ret = sync_filesystem(upper_sb);
- up_read(&upper_sb->s_umount);
+ if (ovl_should_sync(ofs)) {
+ down_read(&upper_sb->s_umount);
+ ret = sync_filesystem(upper_sb);
+ up_read(&upper_sb->s_umount);
+ }
}
return ret;
@@ -411,6 +417,7 @@ enum {
OPT_XINO_AUTO,
OPT_METACOPY_ON,
OPT_METACOPY_OFF,
+ OPT_VOLATILE,
OPT_ERR,
};
@@ -429,6 +436,7 @@ static const match_table_t ovl_tokens = {
{OPT_XINO_AUTO, "xino=auto"},
{OPT_METACOPY_ON, "metacopy=on"},
{OPT_METACOPY_OFF, "metacopy=off"},
+ {OPT_VOLATILE, "volatile"},
{OPT_ERR, NULL}
};
@@ -573,6 +581,10 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
metacopy_opt = true;
break;
+ case OPT_VOLATILE:
+ config->ovl_volatile = true;
+ break;
+
default:
pr_err("unrecognized mount option \"%s\" or missing value\n",
p);
@@ -595,6 +607,11 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->index = false;
}
+ if (!config->upperdir && config->ovl_volatile) {
+ pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
+ config->ovl_volatile = false;
+ }
+
err = ovl_parse_redirect_mode(config, config->redirect_mode);
if (err)
return err;
@@ -1203,6 +1220,45 @@ out_unlock:
return err;
}
+static struct dentry *ovl_lookup_or_create(struct dentry *parent,
+ const char *name, umode_t mode)
+{
+ size_t len = strlen(name);
+ struct dentry *child;
+
+ inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
+ child = lookup_one_len(name, parent, len);
+ if (!IS_ERR(child) && !child->d_inode)
+ child = ovl_create_real(parent->d_inode, child,
+ OVL_CATTR(mode));
+ inode_unlock(parent->d_inode);
+ dput(parent);
+
+ return child;
+}
+
+/*
+ * Creates $workdir/work/incompat/volatile/dirty file if it is not already
+ * present.
+ */
+static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
+{
+ unsigned int ctr;
+ struct dentry *d = dget(ofs->workbasedir);
+ static const char *const volatile_path[] = {
+ OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
+ };
+ const char *const *name = volatile_path;
+
+ for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
+ d = ovl_lookup_or_create(d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
+ if (IS_ERR(d))
+ return PTR_ERR(d);
+ }
+ dput(d);
+ return 0;
+}
+
static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
struct path *workpath)
{
@@ -1286,6 +1342,18 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
goto out;
}
+ /*
+ * For volatile mount, create a incompat/volatile/dirty file to keep
+ * track of it.
+ */
+ if (ofs->config.ovl_volatile) {
+ err = ovl_create_volatile_dirty(ofs);
+ if (err < 0) {
+ pr_err("Failed to create volatile/dirty file.\n");
+ goto out;
+ }
+ }
+
/* Check if upper/work fs supports file handles */
fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
if (ofs->config.index && !fh_type) {
generated by cgit v1.2.3 (git 2.39.0) at 2025-03-02 22:18:10 +0300