From 4188188bdc3aed29eb41fb1537305cff7431d062 Mon Sep 17 00:00:00 2001 From: Curt Wohlgemuth Date: Mon, 5 Mar 2012 10:40:22 -0500 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 Signed-off-by: "Theodore Ts'o" --- fs/ext4/ext4.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 37e7d8b66c99..26ee54b2ce82 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -194,18 +194,25 @@ 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 {