2012-03-02 16:49:04

by Curt Wohlgemuth

Subject: [PATCH] ext4: Add comments to definition of ext4_io_end_t

This should make it more clear what this structure is used
for, and how some of the (mutually exclusive) fields are
used to keep page cache references.

Signed-off-by: Curt Wohlgemuth <[email protected]>
---
fs/ext4/ext4.h | 13 ++++++++++---
1 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 513004f..4dc34ed 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -192,18 +192,25 @@ struct ext4_io_page {

#define MAX_IO_PAGES 128

+/*
+ * For converting uninitialized extents on a work queue.
+ *
+ * 'page' is only used from the writepage() path; 'pages' is only used for
+ * buffered writes; they are used to keep page references until conversion
+ * takes place. For AIO/DIO, neither field is filled in.
+ */
typedef struct ext4_io_end {
struct list_head list; /* per-file finished IO list */
struct inode *inode; /* file being written to */
unsigned int flag; /* unwritten or not */
- struct page *page; /* page struct for buffer write */
+ struct page *page; /* for writepage() path */
loff_t offset; /* offset in the file */
ssize_t size; /* size of the extent */
struct work_struct work; /* data work queue */
struct kiocb *iocb; /* iocb struct for AIO */
int result; /* error value for AIO */
- int num_io_pages;
- struct ext4_io_page *pages[MAX_IO_PAGES];
+ int num_io_pages; /* for writepages() */
+ struct ext4_io_page *pages[MAX_IO_PAGES]; /* for writepages() */
} ext4_io_end_t;

struct ext4_io_submit {
--
1.7.7.3

2012-03-05 15:42:24

by Theodore Ts'o

Subject: Re: [PATCH] ext4: Add comments to definition of ext4_io_end_t

On Fri, Mar 02, 2012 at 08:43:45AM -0800, Curt Wohlgemuth wrote:
> This should make it more clear what this structure is used
> for, and how some of the (mutually exclusive) fields are
> used to keep page cache references.
>
> Signed-off-by: Curt Wohlgemuth <[email protected]>

Thanks, applied.

- Ted