Soon I want to write patches to enable redirects on non-dir files. That means
it is possible that we have to deal with the case where multiple dentries
might be sharing inode and ovl_inode->redirect field setting/resetting
will need to be protected by taking ovl_inode->lock. Current dentry based
locking alone will not be sufficient for this case.
As of now, nlink based code takes ovl_inode->lock in some cases. For redirect
case, during ovl_rename() I might have to take ovl_inode->lock both on
old as well as new ovl_inode. And that means that I need to make sure
there are no deadlocks.
I want to separate out logic for taking lock in a new function. Hence will
need to break down ovl_nlink_start() a bit.
ovl_nlink_start() does the copy up and then takes ovl_inode->lock. Move
copy up related portions in a separate function called ovl_nlink_prep().
This patch is just code reorganization and no funcitonal change.
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/overlayfs/dir.c | 14 ++++++++++++++
fs/overlayfs/overlayfs.h | 1 +
fs/overlayfs/util.c | 26 ++++++++++++++++++--------
3 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 7617a03acc30..1f003be4a19e 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -595,6 +595,10 @@ static int ovl_link(struct dentry *old, struct inode *newdir,
if (err)
goto out_drop_write;
+ err = ovl_nlink_prep(old);
+ if (err)
+ goto out_drop_write;
+
err = ovl_nlink_start(old, &locked);
if (err)
goto out_drop_write;
@@ -752,6 +756,10 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
if (err)
goto out_drop_write;
+ err = ovl_nlink_prep(dentry);
+ if (err)
+ goto out_drop_write;
+
err = ovl_nlink_start(dentry, &locked);
if (err)
goto out_drop_write;
@@ -960,6 +968,12 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
if (err)
goto out_drop_write;
} else {
+ err = ovl_nlink_prep(new);
+ if (err)
+ goto out_drop_write;
+ }
+
+ if (overwrite) {
err = ovl_nlink_start(new, &new_locked);
if (err)
goto out_drop_write;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 214d9f08c574..aa5b0c121fc7 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -271,6 +271,7 @@ bool ovl_test_flag(unsigned long flag, struct inode *inode);
bool ovl_inuse_trylock(struct dentry *dentry);
void ovl_inuse_unlock(struct dentry *dentry);
bool ovl_need_index(struct dentry *dentry);
+int ovl_nlink_prep(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry, bool *locked);
void ovl_nlink_end(struct dentry *dentry, bool locked);
int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 394674c4c820..ed93e233894f 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -675,15 +675,9 @@ static void ovl_cleanup_index(struct dentry *dentry)
goto out;
}
-/*
- * Operations that change overlay inode and upper inode nlink need to be
- * synchronized with copy up for persistent nlink accounting.
- */
-int ovl_nlink_start(struct dentry *dentry, bool *locked)
+int ovl_nlink_prep(struct dentry *dentry)
{
- struct ovl_inode *oi = OVL_I(d_inode(dentry));
- const struct cred *old_cred;
- int err;
+ int err = 0;
if (!d_inode(dentry))
return 0;
@@ -708,6 +702,22 @@ int ovl_nlink_start(struct dentry *dentry, bool *locked)
return err;
}
+ return err;
+}
+
+/*
+ * Operations that change overlay inode and upper inode nlink need to be
+ * synchronized with copy up for persistent nlink accounting.
+ */
+int ovl_nlink_start(struct dentry *dentry, bool *locked)
+{
+ struct ovl_inode *oi = OVL_I(d_inode(dentry));
+ const struct cred *old_cred;
+ int err;
+
+ if (!d_inode(dentry))
+ return 0;
+
err = mutex_lock_interruptible(&oi->lock);
if (err)
return err;
--
2.13.6
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