2014/1/17 One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx>:
>> +#define ESHAREDENIED 258 /* File is locked with a sharelock */
>
> Have you prepared C library patches to match this ?
I don't have it for now.
>
> (and why not just use EPERM, it has the meaning you want already)
We need to determine if we have a share reservation error to map it
accurately in file servers and wine.
>
>
>> + * Check to see if there's a share_reservation conflict. LOCK_READ/LOCK_WRITE
>> + * tell us whether the reservation allows other readers and writers.
>> + */
>> +static int
>> +locks_mand_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
>> +{
>
> Shouldn't this also check for CAP_SYS_DAC or some similar permission so
> that root can override such a mess (eg to fix full disks in an
> emergency) ?
May be it's better to let root an ability to remount the system
without sharelock mount option and then fix an emergency?
>
>
>> +
>> + /*
>> + * For sharelock mounts if a file was created but not opened, we need
>> + * to keep parent i_mutex until we finish the open to prevent races when
>> + * somebody opens newly created by us file and locks it with a sharelock
>> + * before we open it.
>> + */
>> + if (IS_SHARELOCK(dir->d_inode) && error > 0 && *opened & FILE_CREATED) {
>> + /* Don't check for write permission, don't truncate */
>> + open_flag &= ~O_TRUNC;
>> + will_truncate = false;
>> + acc_mode = MAY_OPEN;
>> + path_to_nameidata(path, nd);
>> +
>> + error = may_open(&nd->path, acc_mode, open_flag);
>> + if (error) {
>> + mutex_unlock(&dir->d_inode->i_mutex);
>> + goto out;
>> + }
>> + file->f_path.mnt = nd->path.mnt;
>> + error = finish_open(file, nd->path.dentry, NULL, opened);
>> + if (error) {
>> + mutex_unlock(&dir->d_inode->i_mutex);
>> + if (error == -EOPENSTALE)
>> + goto stale_open;
>> + goto out;
>> + }
>> + error = sharelock_lock_file(file);
>> + mutex_unlock(&dir->d_inode->i_mutex);
>> + if (error)
>> + goto exit_fput;
>> + goto opened;
>> + }
>> +
>> mutex_unlock(&dir->d_inode->i_mutex);
>
> What stops the file system changing mount flags via a remount between
> these two ?
Nothing, but it doesn't bring problems here: if the first IS_SHARELOCK
condition is true, we don't get into the second (see 'goto opened').
>
>>
>> if (error <= 0) {
>> @@ -3034,6 +3073,18 @@ finish_open_created:
>> goto stale_open;
>> goto out;
>> }
>> +
>> + if (IS_SHARELOCK(dir->d_inode)) {
>> + /*
>> + * Lock parent i_mutex to prevent races with sharelocks on
>> + * newly created files.
>> + */
>> + mutex_lock(&dir->d_inode->i_mutex);
>> + error = sharelock_lock_file(file);
>> + mutex_unlock(&dir->d_inode->i_mutex);
>> + if (error)
>> + goto exit_fput;
>> + }
>> opened:
> --
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--
Best regards,
Pavel Shilovsky.
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