On Fri, Apr 24, 2020 at 05:49:00PM +0300, Amir Goldstein wrote:
> I didn't mean we need to check if link_max is valid range for upper fs.
> We anyway use minimum of user requested value and upper fs max.
>
> Frankly, I think there are only two sane options for system wide configuration:
> 1. disable whiteout link
> 2. enable whiteout link with ofs->workdir->d_sb->s_max_links
And that one doesn't work, see for example ext4, which defines EXT4_LINK_MAX but
doesn't set s_max_links. This could be fixed, but using EMLINK to detect the
max-link condition is simpler and more reliable.
And I don't really see a reason to disable whiteout hard links. What scenario
would that be useful in?
Updated patch below. Changes from v5:
- fix a missing dput on shutdown
- don't poass workdir to ovl_cleanup_and_whiteout/ovl_whiteout
- flatten out retry loop in ovl_whiteout
- use EMLINK to distinguish max-links from misc failure
Thanks,
Miklos
---
From: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
Subject: ovl: whiteout inode sharing
Date: Fri, 24 Apr 2020 10:55:17 +0800
Share inode with different whiteout files for saving inode and speeding up
delete operation.
If EMLINK is encountered when linking a shared whiteout, create a new one.
In case of any other error, disable sharing for this super block.
Note: ofs->whiteout is protected by inode lock on workdir.
Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/overlayfs/dir.c | 49 +++++++++++++++++++++++++++++++++++------------
fs/overlayfs/overlayfs.h | 2 -
fs/overlayfs/ovl_entry.h | 3 ++
fs/overlayfs/readdir.c | 2 -
fs/overlayfs/super.c | 4 +++
fs/overlayfs/util.c | 3 +-
6 files changed, 48 insertions(+), 15 deletions(-)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -62,35 +62,59 @@ struct dentry *ovl_lookup_temp(struct de
}
/* caller holds i_mutex on workdir */
-static struct dentry *ovl_whiteout(struct dentry *workdir)
+static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
{
int err;
struct dentry *whiteout;
+ struct dentry *workdir = ofs->workdir;
struct inode *wdir = workdir->d_inode;
- whiteout = ovl_lookup_temp(workdir);
- if (IS_ERR(whiteout))
- return whiteout;
+ if (!ofs->whiteout) {
+ whiteout = ovl_lookup_temp(workdir);
+ if (IS_ERR(whiteout))
+ return whiteout;
+
+ err = ovl_do_whiteout(wdir, whiteout);
+ if (err) {
+ dput(whiteout);
+ return ERR_PTR(err);
+ }
+ ofs->whiteout = whiteout;
+ }
- err = ovl_do_whiteout(wdir, whiteout);
- if (err) {
+ if (ofs->share_whiteout) {
+ whiteout = ovl_lookup_temp(workdir);
+ if (IS_ERR(whiteout))
+ goto fallback;
+
+ err = ovl_do_link(ofs->whiteout, wdir, whiteout);
+ if (!err)
+ goto success;
+
+ if (err != -EMLINK) {
+ pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
+ ofs->whiteout->d_inode->i_nlink, err);
+ ofs->share_whiteout = false;
+ }
dput(whiteout);
- whiteout = ERR_PTR(err);
}
-
+fallback:
+ whiteout = ofs->whiteout;
+ ofs->whiteout = NULL;
+success:
return whiteout;
}
/* Caller must hold i_mutex on both workdir and dir */
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
struct dentry *dentry)
{
- struct inode *wdir = workdir->d_inode;
+ struct inode *wdir = ofs->workdir->d_inode;
struct dentry *whiteout;
int err;
int flags = 0;
- whiteout = ovl_whiteout(workdir);
+ whiteout = ovl_whiteout(ofs);
err = PTR_ERR(whiteout);
if (IS_ERR(whiteout))
return err;
@@ -715,6 +739,7 @@ static bool ovl_matches_upper(struct den
static int ovl_remove_and_whiteout(struct dentry *dentry,
struct list_head *list)
{
+ struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
struct dentry *workdir = ovl_workdir(dentry);
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct dentry *upper;
@@ -748,7 +773,7 @@ static int ovl_remove_and_whiteout(struc
goto out_dput_upper;
}
- err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
+ err = ovl_cleanup_and_whiteout(ofs, d_inode(upperdir), upper);
if (err)
goto out_d_drop;
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -455,7 +455,7 @@ static inline void ovl_copyflags(struct
/* dir.c */
extern const struct inode_operations ovl_dir_inode_operations;
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
struct dentry *dentry);
struct ovl_cattr {
dev_t rdev;
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -68,6 +68,7 @@ struct ovl_fs {
/* Did we take the inuse lock? */
bool upperdir_locked;
bool workdir_locked;
+ bool share_whiteout;
/* Traps in ovl inode cache */
struct inode *upperdir_trap;
struct inode *workbasedir_trap;
@@ -77,6 +78,8 @@ struct ovl_fs {
int xino_mode;
/* For allocation of non-persistent inode numbers */
atomic_long_t last_ino;
+ /* Whiteout dentry cache */
+ struct dentry *whiteout;
};
static inline struct ovl_fs *OVL_FS(struct super_block *sb)
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -1154,7 +1154,7 @@ int ovl_indexdir_cleanup(struct ovl_fs *
* Whiteout orphan index to block future open by
* handle after overlay nlink dropped to zero.
*/
- err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+ err = ovl_cleanup_and_whiteout(ofs, dir, index);
} else {
/* Cleanup orphan index entries */
err = ovl_cleanup(dir, index);
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -707,7 +707,8 @@ static void ovl_cleanup_index(struct den
index = NULL;
} else if (ovl_index_all(dentry->d_sb)) {
/* Whiteout orphan index to block future open by handle */
- err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+ err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
+ dir, index);
} else {
/* Cleanup orphan index entries */
err = ovl_cleanup(dir, index);
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -217,6 +217,7 @@ static void ovl_free_fs(struct ovl_fs *o
iput(ofs->indexdir_trap);
iput(ofs->workdir_trap);
iput(ofs->upperdir_trap);
+ dput(ofs->whiteout);
dput(ofs->indexdir);
dput(ofs->workdir);
if (ofs->workdir_locked)
@@ -1776,6 +1777,9 @@ static int ovl_fill_super(struct super_b
if (!cred)
goto out_err;
+ /* Is there a reason anyone would want not to share whiteouts? */
+ ofs->share_whiteout = true;
+
ofs->config.index = ovl_index_def;
ofs->config.nfs_export = ovl_nfs_export_def;
ofs->config.xino = ovl_xino_def();
