[RFC PATCH v3 01/18] block: Add check for async buffered writes to generic_write_checks

Stefan Roesch
2022-05-18T23:37:25Z

This introduces the flag FMODE_BUF_WASYNC. If devices support async
buffered writes, this flag can be set. It also modifies the check in
generic_write_checks to take async buffered writes into consideration.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
fs/read_write.c | 4 +++-
include/linux/fs.h | 3 +++
2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index e643aec2b0ef..544d4df33f4f 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1633,7 +1633,9 @@ int generic_write_checks_count(struct kiocb *iocb, loff_t *count)
if (iocb->ki_flags & IOCB_APPEND)
iocb->ki_pos = i_size_read(inode);

- if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
+ if ((iocb->ki_flags & IOCB_NOWAIT) &&
+ !((iocb->ki_flags & IOCB_DIRECT) ||
+ (file->f_mode & FMODE_BUF_WASYNC)))
return -EINVAL;

return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, count);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bbde95387a23..3b479d02e210 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -177,6 +177,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
/* File supports async buffered reads */
#define FMODE_BUF_RASYNC ((__force fmode_t)0x40000000)

+/* File supports async nowait buffered writes */
+#define FMODE_BUF_WASYNC ((__force fmode_t)0x80000000)
+
/*
* Attribute flags. These should be or-ed together to figure out what
* has been changed!
--
2.30.2