When nfsd caches a file, we want to be able to close it down in advance of setlease attempts. Setting a lease is generally done at the behest of userland, so we need a mechanism to ensure that a userland task can completely close a file without having to return back to userspace. To do this, we borrow the global delayed_fput infrastructure that kthreads use. fput_global will queue to the global_fput list if the last reference was put. The caller can then use fput_global_flush to force the final __fput to run. While we're at it, export fput_global_flush as nfsd will need to use that as well. Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx> --- fs/file_table.c | 33 +++++++++++++++++++++++++++++++++ include/linux/file.h | 1 + 2 files changed, 34 insertions(+) diff --git a/fs/file_table.c b/fs/file_table.c index 0bf8ddc680ab..d214c45765e6 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -262,6 +262,7 @@ void fput_global_flush(void) { flush_delayed_work(&global_fput_work); } +EXPORT_SYMBOL(fput_global_flush); /** * fput - put a struct file reference @@ -304,6 +305,38 @@ void fput(struct file *file) } EXPORT_SYMBOL(fput); +/** + * fput_global - do an fput without using task_work + * @file: file of which to put the reference + * + * 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 global_fput infrastructure that + * kthreads use. The userland process can use fput_global() on one or more + * struct files and then call fput_global_flush() to ensure that they are + * completely closed before proceeding. + * + * The main user is nfsd, which uses this to ensure that all cached but + * otherwise unused files are closed to allow a userland request for a lease + * to proceed. + * + * Returns true if the final fput was done, false otherwise. The caller can + * use this to determine whether to fput_global_flush afterward. + */ +bool fput_global(struct file *file) +{ + if (atomic_long_dec_and_test(&file->f_count)) { + if (llist_add(&file->f_u.fu_llist, &global_fput_list)) + schedule_delayed_work(&global_fput_work, 1); + return true; + } + return false; +} +EXPORT_SYMBOL(fput_global); + /* * synchronous analog of fput(); for kernel threads that might be needed * in some umount() (and thus can't use fput_global_flush() without diff --git a/include/linux/file.h b/include/linux/file.h index 73bb7cee57e9..7803aed00271 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -12,6 +12,7 @@ struct file; extern void fput(struct file *); +extern bool fput_global(struct file *); struct file_operations; struct vfsmount; -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html