linux-ext4 - [PATCH 03/11] vfs: add nowait flag for struct dir

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Date:   Sun, 27 Aug 2023 21:28:27 +0800
From:   Hao Xu <hao.xu@...ux.dev>
To:     io-uring@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Cc:     Dominique Martinet <asmadeus@...ewreck.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        Christian Brauner <brauner@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Stefan Roesch <shr@...com>, Clay Harris <bugs@...ycon.org>,
        Dave Chinner <david@...morbit.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-cachefs@...hat.com,
        ecryptfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-unionfs@...r.kernel.org, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-btrfs@...r.kernel.org, codalist@...a.cs.cmu.edu,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-mm@...ck.org, linux-nilfs@...r.kernel.org,
        devel@...ts.orangefs.org, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-mtd@...ts.infradead.org,
        Wanpeng Li <wanpengli@...cent.com>
Subject: [PATCH 03/11] vfs: add nowait flag for struct dir_context

From: Hao Xu <howeyxu@...cent.com>

The flags will allow passing DIR_CONTEXT_F_NOWAIT to iterate()
implementations that support it (as signaled through FMODE_NWAIT
in file->f_mode)

Notes:
- considered using IOCB_NOWAIT but if we add more flags later it
would be confusing to keep track of which values are valid, use
dedicated flags
- might want to check ctx.flags & DIR_CONTEXT_F_NOWAIT is only set
when file->f_mode & FMODE_NOWAIT in iterate_dir() as e.g. WARN_ONCE?

Co-developed-by: Dominique Martinet <asmadeus@...ewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
Signed-off-by: Hao Xu <howeyxu@...cent.com>
---
 fs/internal.h      | 2 +-
 fs/readdir.c       | 6 ++++--
 include/linux/fs.h | 8 ++++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/internal.h b/fs/internal.h
index b1f66e52d61b..7508d485c655 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -311,4 +311,4 @@ void mnt_idmap_put(struct mnt_idmap *idmap);
 struct linux_dirent64;
 
 int vfs_getdents(struct file *file, struct linux_dirent64 __user *dirent,
-		 unsigned int count);
+		 unsigned int count, unsigned long flags);
diff --git a/fs/readdir.c b/fs/readdir.c
index 9592259b7e7f..b80caf4c9321 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -358,12 +358,14 @@ static bool filldir64(struct dir_context *ctx, const char *name, int namlen,
  * @file    : pointer to file struct of directory
  * @dirent  : pointer to user directory structure
  * @count   : size of buffer
+ * @flags   : additional dir_context flags
  */
 int vfs_getdents(struct file *file, struct linux_dirent64 __user *dirent,
-		 unsigned int count)
+		 unsigned int count, unsigned long flags)
 {
 	struct getdents_callback64 buf = {
 		.ctx.actor = filldir64,
+		.ctx.flags = flags,
 		.count = count,
 		.current_dir = dirent
 	};
@@ -395,7 +397,7 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 	if (!f.file)
 		return -EBADF;
 
-	error = vfs_getdents(f.file, dirent, count);
+	error = vfs_getdents(f.file, dirent, count, 0);
 
 	fdput_pos(f);
 	return error;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6867512907d6..f3e315e8efdd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1719,8 +1719,16 @@ typedef bool (*filldir_t)(struct dir_context *, const char *, int, loff_t, u64,
 struct dir_context {
 	filldir_t actor;
 	loff_t pos;
+	unsigned long flags;
 };
 
+/*
+ * flags for dir_context flags
+ * DIR_CONTEXT_F_NOWAIT: Request non-blocking iterate
+ *                       (requires file->f_mode & FMODE_NOWAIT)
+ */
+#define DIR_CONTEXT_F_NOWAIT	(1 << 0)
+
 /*
  * These flags let !MMU mmap() govern direct device mapping vs immediate
  * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
-- 
2.25.1