| Message ID | 1442238355-8203-4-git-send-email-jeff.layton@primarydata.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Sep 14, 2015 at 09:45:54AM -0400, Jeff Layton wrote: > +/** > + * fput_queue - do an fput without using task_work > + * @file: file of which to put the reference > + * > + * If we need to ensure that the final __fput is done on a file before > + * returning to userland, then we can't queue it to task_work. For that we ????????? > + * borrow the infrastructure used by kthreads, and the task can then just > + * called flush_delayed_fput to ensure that the final fput has completed. Are you sure that it's not a typo? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 14 Sep 2015 15:15:39 +0100 Al Viro <viro@ZenIV.linux.org.uk> wrote: > On Mon, Sep 14, 2015 at 09:45:54AM -0400, Jeff Layton wrote: > > +/** > > + * fput_queue - do an fput without using task_work > > + * @file: file of which to put the reference > > + * > > + * If we need to ensure that the final __fput is done on a file before > > + * returning to userland, then we can't queue it to task_work. For that we > ????????? > > + * borrow the infrastructure used by kthreads, and the task can then just > > + * called flush_delayed_fput to ensure that the final fput has completed. > > Are you sure that it's not a typo? I don't think so, but it could be clearer. Something like this maybe? "then we can't queue it via task_work_add."
On Mon, Sep 14, 2015 at 10:19:18AM -0400, Jeff Layton wrote: > > > + * borrow the infrastructure used by kthreads, and the task can then just > > > + * called flush_delayed_fput to ensure that the final fput has completed. > > > > Are you sure that it's not a typo? > > I don't think so, but it could be clearer. Something like this maybe? > > "then we can't queue it via task_work_add." Huh? task_work_add() callbacks *will* run before we return to userland -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 14 Sep 2015 17:39:54 +0100 Al Viro <viro@ZenIV.linux.org.uk> wrote: > On Mon, Sep 14, 2015 at 10:19:18AM -0400, Jeff Layton wrote: > > > > + * borrow the infrastructure used by kthreads, and the task can then just > > > > + * called flush_delayed_fput to ensure that the final fput has completed. > > > > > > Are you sure that it's not a typo? > > > > I don't think so, but it could be clearer. Something like this maybe? > > > > "then we can't queue it via task_work_add." > > Huh? > > task_work_add() callbacks *will* run before we return to userland Right, but only just before. We need it to run before we try to set the lease in the context of a fcntl() call. How about this text instead then? I'll fix up the patch if this sounds reasonable: "When fput is called in the context of a userland process, it'll queue the actual work (__fput()) to be done just before returning to userland. In some cases however, we need to ensure that the __fput runs before that point. There is no safe way to flush work that has been queued via task_work_add however, so to do this we borrow the delayed_fput infrastructure that kthreads use. The userland process can use fput_queue() on one or more struct files and then call flush_delayed_fput() to ensure that they are completely closed."
diff --git a/fs/file_table.c b/fs/file_table.c index d63f4a399d39..1ad2e3fd2064 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -297,6 +297,24 @@ void fput(struct file *file) } EXPORT_SYMBOL(fput); +/** + * fput_queue - do an fput without using task_work + * @file: file of which to put the reference + * + * If we need to ensure that the final __fput is done on a file before + * returning to userland, then we can't queue it to task_work. For that we + * borrow the infrastructure used by kthreads, and the task can then just + * called flush_delayed_fput to ensure that the final fput has completed. + */ +void fput_queue(struct file *file) +{ + if (atomic_long_dec_and_test(&file->f_count)) { + if (llist_add(&file->f_u.fu_llist, &delayed_fput_list)) + schedule_delayed_work(&delayed_fput_work, 1); + } +} +EXPORT_SYMBOL(fput_queue); + /* * synchronous analog of fput(); for kernel threads that might be needed * in some umount() (and thus can't use flush_delayed_fput() without diff --git a/include/linux/file.h b/include/linux/file.h index f87d30882a24..543b0e2faf2c 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -12,6 +12,7 @@ struct file; extern void fput(struct file *); +extern void fput_queue(struct file *); struct file_operations; struct vfsmount;
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com> --- fs/file_table.c | 18 ++++++++++++++++++ include/linux/file.h | 1 + 2 files changed, 19 insertions(+)