[PATCH 03/11] vfs: add nowait flag for struct dir_context

Hao Xu
2023-08-27T13:33:03Z

From: Hao Xu <howeyxu@tencent.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@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Hao Xu <howeyxu@tencent.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