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ext4: make ext4_bio_write_page() use BH_Async_Write flags

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So far ext4_bio_write_page() attached all the pages to ext4_io_end
structure.  This makes that structure pretty heavy (1 KB for pointers
+ 16 bytes per page attached to the bio).  Also later we would like to
share ext4_io_end structure among several bios in case IO to a single
extent needs to be split among several bios and pointing to pages from
ext4_io_end makes this complex.

We remove page pointers from ext4_io_end and use pointers from bio
itself instead.  This isn't as easy when blocksize < pagesize because
then we can have several bios in flight for a single page and we have
to be careful when to call end_page_writeback().  However this is a
known problem already solved by block_write_full_page() /
end_buffer_async_write() so we mimic its behavior here.  We mark
buffers going to disk with BH_Async_Write flag and in
ext4_bio_end_io() we check whether there are any buffers with
BH_Async_Write flag left.  If there are not, we can call
end_page_writeback().

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
This commit is contained in:
Jan Kara 2013-04-11 23:48:32 -04:00 • committed by Theodore Ts'o
parent e1091b157c
commit 0058f9658c
2 changed files with 77 additions and 100 deletions
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14
fs/ext4/ext4.h
View file

@ -198,19 +198,8 @@ struct mpage_da_data {
#define EXT4_IO_END_ERROR 0x0002
#define EXT4_IO_END_DIRECT 0x0004
struct ext4_io_page {
struct page *p_page;
atomic_t p_count;
};
#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 */
@ -220,15 +209,12 @@ typedef struct ext4_io_end {
ssize_t size; /* size of the extent */
struct kiocb *iocb; /* iocb struct for AIO */
int result; /* error value for AIO */
int num_io_pages; /* for writepages() */
struct ext4_io_page *pages[MAX_IO_PAGES]; /* for writepages() */
} ext4_io_end_t;
struct ext4_io_submit {
int io_op;
struct bio *io_bio;
ext4_io_end_t *io_end;
struct ext4_io_page *io_page;
sector_t io_next_block;
};