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

[Hao Xu]

From: Hao Xu <howe...@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 <asmad...@codewreck.org>
Signed-off-by: Dominique Martinet <asmad...@codewreck.org>
Signed-off-by: Hao Xu <howe...@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

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