On Mon, Jan 16, 2017 at 1:05 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Sun, Jan 15, 2017 at 2:57 PM, Amir Goldstein <amir73il@xxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
>> ---
>> 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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