[6/6] ovl: concurrent copy up of regular files
diff mbox

Message ID 1484488652-611-7-git-send-email-amir73il@gmail.com
State New
Headers show

Commit Message

Amir Goldstein Jan. 15, 2017, 1:57 p.m. UTC
Now that copy up of regular file is done using O_TMPFILE,
we don't need to hold rename_lock throughout copy up.

Use the copy up waitqueue to synchronize concurrent copy up
of the same file. Different regular files can be copied up
concurrently.

The upper dir inode_lock is taken instead of rename_lock,
because it is needed for lookup and later for linking the
temp file, but it is released while copying up data.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/copy_up.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

Comments

Miklos Szeredi Jan. 16, 2017, 11:05 a.m. UTC | #1
On Sun, Jan 15, 2017 at 2:57 PM, Amir Goldstein <amir73il@gmail.com> wrote:
> Now that copy up of regular file is done using O_TMPFILE,
> we don't need to hold rename_lock throughout copy up.
>
> Use the copy up waitqueue to synchronize concurrent copy up
> of the same file. Different regular files can be copied up
> concurrently.
>
> The upper dir inode_lock is taken instead of rename_lock,
> because it is needed for lookup and later for linking the
> temp file, but it is released while copying up data.
>
> Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/overlayfs/copy_up.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index d3b6c15..ddf5e2d 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -291,7 +291,14 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
>                 BUG_ON(upperpath.dentry != NULL);
>                 upperpath.dentry = temp;
>
> +               if (tmpfile)
> +                       inode_unlock(udir);
> +
>                 err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
> +
> +               if (tmpfile)
> +                       inode_lock_nested(udir, I_MUTEX_PARENT);
> +
>                 if (err)
>                         goto out_cleanup;
>         }
> @@ -371,6 +378,19 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
>                         return PTR_ERR(link);
>         }
>
> +       if (tmpfile) {
> +               err = ovl_copy_up_start(dentry);
> +               /* err < 0: interrupted, err > 0: raced with another copy-up */
> +               if (unlikely(err)) {
> +                       pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
> +                       if (err > 0)
> +                               err = 0;
> +                       goto out_done;
> +               }
> +               /* lock_rename/unlock_rename will lock/unlock only upperdir */
> +               workdir = upperdir;

Unnecessary obfuscation.   Just do lock_inode(); ovl_copy_up_locked();
unlokc_inode();.

Thanks,
Miklos

> +       }
> +
>         err = -EIO;
>         if (lock_rename(workdir, upperdir) != NULL) {
>                 pr_err("overlayfs: failed to lock workdir+upperdir\n");
> @@ -390,6 +410,9 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
>         }
>  out_unlock:
>         unlock_rename(workdir, upperdir);
> +       if (tmpfile)
> +               ovl_copy_up_end(dentry);
> +out_done:
>         do_delayed_call(&done);
>
>         return err;
> --
> 2.7.4
>
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Amir Goldstein Jan. 16, 2017, 11:31 a.m. UTC | #2
On Mon, Jan 16, 2017 at 1:05 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Sun, Jan 15, 2017 at 2:57 PM, Amir Goldstein <amir73il@gmail.com> wrote:
>> Now that copy up of regular file is done using O_TMPFILE,
>> we don't need to hold rename_lock throughout copy up.
>>
>> Use the copy up waitqueue to synchronize concurrent copy up
>> of the same file. Different regular files can be copied up
>> concurrently.
>>
>> The upper dir inode_lock is taken instead of rename_lock,
>> because it is needed for lookup and later for linking the
>> temp file, but it is released while copying up data.
>>
>> Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
>> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>> ---
>>  fs/overlayfs/copy_up.c | 23 +++++++++++++++++++++++
>>  1 file changed, 23 insertions(+)
>>
>> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
>> index d3b6c15..ddf5e2d 100644
>> --- a/fs/overlayfs/copy_up.c
>> +++ b/fs/overlayfs/copy_up.c
>> @@ -291,7 +291,14 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
>>                 BUG_ON(upperpath.dentry != NULL);
>>                 upperpath.dentry = temp;
>>
>> +               if (tmpfile)
>> +                       inode_unlock(udir);
>> +
>>                 err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
>> +
>> +               if (tmpfile)
>> +                       inode_lock_nested(udir, I_MUTEX_PARENT);
>> +
>>                 if (err)
>>                         goto out_cleanup;
>>         }
>> @@ -371,6 +378,19 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
>>                         return PTR_ERR(link);
>>         }
>>
>> +       if (tmpfile) {
>> +               err = ovl_copy_up_start(dentry);
>> +               /* err < 0: interrupted, err > 0: raced with another copy-up */
>> +               if (unlikely(err)) {
>> +                       pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
>> +                       if (err > 0)
>> +                               err = 0;
>> +                       goto out_done;
>> +               }
>> +               /* lock_rename/unlock_rename will lock/unlock only upperdir */
>> +               workdir = upperdir;
>
> Unnecessary obfuscation.   Just do lock_inode(); ovl_copy_up_locked();
> unlokc_inode();.
>

upperdir still needs to be locked for ovl_set_timestamps(), so I can do:

+                    inode_lock_nested(udir, I_MUTEX_PARENT)
+           } else {
>>         if (lock_rename(workdir, upperdir) != NULL) {
>>                 pr_err("overlayfs: failed to lock workdir+upperdir\n");
...
>>  out_unlock:
+             if (tmpfile)
+                     inode_unlock(udir);
+             else
>>         unlock_rename(workdir, upperdir);
>> +       if (tmpfile)
>> +               ovl_copy_up_end(dentry);
>> +out_done:
>>         do_delayed_call(&done);
>>
>>         return err;
>> --
>> 2.7.4
>>
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Patch
diff mbox

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index d3b6c15..ddf5e2d 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -291,7 +291,14 @@  static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
 		BUG_ON(upperpath.dentry != NULL);
 		upperpath.dentry = temp;
 
+		if (tmpfile)
+			inode_unlock(udir);
+
 		err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
+
+		if (tmpfile)
+			inode_lock_nested(udir, I_MUTEX_PARENT);
+
 		if (err)
 			goto out_cleanup;
 	}
@@ -371,6 +378,19 @@  static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 			return PTR_ERR(link);
 	}
 
+	if (tmpfile) {
+		err = ovl_copy_up_start(dentry);
+		/* err < 0: interrupted, err > 0: raced with another copy-up */
+		if (unlikely(err)) {
+			pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
+			if (err > 0)
+				err = 0;
+			goto out_done;
+		}
+		/* lock_rename/unlock_rename will lock/unlock only upperdir */
+		workdir = upperdir;
+	}
+
 	err = -EIO;
 	if (lock_rename(workdir, upperdir) != NULL) {
 		pr_err("overlayfs: failed to lock workdir+upperdir\n");
@@ -390,6 +410,9 @@  static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 	}
 out_unlock:
 	unlock_rename(workdir, upperdir);
+	if (tmpfile)
+		ovl_copy_up_end(dentry);
+out_done:
 	do_delayed_call(&done);
 
 	return err;