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ovl: whiteout inode sharing

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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@mykernel.net>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Chengguang Xu
2020-04-24 10:55:17 +08:00
committed by Miklos Szeredi
parent 654255fa20
commit c21c839b84
6 changed files with 48 additions and 15 deletions
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49
fs/overlayfs/dir.c
View File

@@ -62,35 +62,59 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
}
/* 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))
goto out;
err = ovl_do_whiteout(wdir, whiteout);
if (err) {
dput(whiteout);
whiteout = ERR_PTR(err);
err = ovl_do_whiteout(wdir, whiteout);
if (err) {
dput(whiteout);
whiteout = ERR_PTR(err);
goto out;
}
ofs->whiteout = whiteout;
}
if (ofs->share_whiteout) {
whiteout = ovl_lookup_temp(workdir);
if (IS_ERR(whiteout))
goto out;
err = ovl_do_link(ofs->whiteout, wdir, whiteout);
if (!err)
goto out;
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 = ofs->whiteout;
ofs->whiteout = NULL;
out:
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 dentry *dentry, struct dentry *upper)
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(struct dentry *dentry,
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;