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mm: make snapshotting pages for stable writes a per-bio operation

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Walking a bio's page mappings has proved problematic, so create a new
bio flag to indicate that a bio's data needs to be snapshotted in order
to guarantee stable pages during writeback.  Next, for the one user
(ext3/jbd) of snapshotting, hook all the places where writes can be
initiated without PG_writeback set, and set BIO_SNAP_STABLE there.

We must also flag journal "metadata" bios for stable writeout, since
file data can be written through the journal.  Finally, the
MS_SNAP_STABLE mount flag (only used by ext3) is now superfluous, so get
rid of it.

[akpm@linux-foundation.org: rename _submit_bh()'s `flags' to `bio_flags', delobotomize the _submit_bh declaration]
[akpm@linux-foundation.org: teeny cleanup]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Darrick J. Wong 2013-04-29 15:07:25 -07:00 committed by Linus Torvalds
parent 106c992a5e
commit 7136851117
8 changed files with 34 additions and 31 deletions
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9
fs/buffer.c
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@ -2949,7 +2949,7 @@ static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
}
}
int submit_bh(int rw, struct buffer_head * bh)
int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
{
struct bio *bio;
int ret = 0;
@ -2984,6 +2984,7 @@ int submit_bh(int rw, struct buffer_head * bh)
bio->bi_end_io = end_bio_bh_io_sync;
bio->bi_private = bh;
bio->bi_flags |= bio_flags;
/* Take care of bh's that straddle the end of the device */
guard_bh_eod(rw, bio, bh);
@ -2997,6 +2998,12 @@ int submit_bh(int rw, struct buffer_head * bh)
bio_put(bio);
return ret;
}
EXPORT_SYMBOL_GPL(_submit_bh);
int submit_bh(int rw, struct buffer_head *bh)
{
return _submit_bh(rw, bh, 0);
}
EXPORT_SYMBOL(submit_bh);
/**

1
fs/ext3/super.c
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@ -2067,7 +2067,6 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
test_opt(sb,DATA_FLAGS) == EXT3_MOUNT_JOURNAL_DATA ? "journal":
test_opt(sb,DATA_FLAGS) == EXT3_MOUNT_ORDERED_DATA ? "ordered":
"writeback");
sb->s_flags |= MS_SNAP_STABLE;
return 0;

25
fs/jbd/commit.c
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@ -162,8 +162,17 @@ static void journal_do_submit_data(struct buffer_head **wbuf, int bufs,
for (i = 0; i < bufs; i++) {
wbuf[i]->b_end_io = end_buffer_write_sync;
/* We use-up our safety reference in submit_bh() */
submit_bh(write_op, wbuf[i]);
/*
* Here we write back pagecache data that may be mmaped. Since
* we cannot afford to clean the page and set PageWriteback
* here due to lock ordering (page lock ranks above transaction
* start), the data can change while IO is in flight. Tell the
* block layer it should bounce the bio pages if stable data
* during write is required.
*
* We use up our safety reference in submit_bh().
*/
_submit_bh(write_op, wbuf[i], 1 << BIO_SNAP_STABLE);
}
}
@ -667,7 +676,17 @@ start_journal_io:
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
bh->b_end_io = journal_end_buffer_io_sync;
submit_bh(write_op, bh);
/*
* In data=journal mode, here we can end up
* writing pagecache data that might be
* mmapped. Since we can't afford to clean the
* page and set PageWriteback (see the comment
* near the other use of _submit_bh()), the
* data can change while the write is in
* flight. Tell the block layer to bounce the
* bio pages if stable pages are required.
*/
_submit_bh(write_op, bh, 1 << BIO_SNAP_STABLE);
}
cond_resched();

3
include/linux/blk_types.h
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@ -111,12 +111,13 @@ struct bio {
#define BIO_FS_INTEGRITY 9 /* fs owns integrity data, not block layer */
#define BIO_QUIET 10 /* Make BIO Quiet */
#define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
#define BIO_SNAP_STABLE 12 /* bio data must be snapshotted during write */
/*
* Flags starting here get preserved by bio_reset() - this includes
* BIO_POOL_IDX()
*/
#define BIO_RESET_BITS 12
#define BIO_RESET_BITS 13
#define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))

1
include/linux/buffer_head.h
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@ -181,6 +181,7 @@ void ll_rw_block(int, int, struct buffer_head * bh[]);
int sync_dirty_buffer(struct buffer_head *bh);
int __sync_dirty_buffer(struct buffer_head *bh, int rw);
void write_dirty_buffer(struct buffer_head *bh, int rw);
int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags);
int submit_bh(int, struct buffer_head *);
void write_boundary_block(struct block_device *bdev,
sector_t bblock, unsigned blocksize);

1
include/uapi/linux/fs.h
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@ -88,7 +88,6 @@ struct inodes_stat_t {
#define MS_STRICTATIME (1<<24) /* Always perform atime updates */
/* These sb flags are internal to the kernel */
#define MS_SNAP_STABLE (1<<27) /* Snapshot pages during writeback, if needed */
#define MS_NOSEC (1<<28)
#define MS_BORN (1<<29)
#define MS_ACTIVE (1<<30)

21
mm/bounce.c
View File

@ -181,32 +181,13 @@ static void bounce_end_io_read_isa(struct bio *bio, int err)
#ifdef CONFIG_NEED_BOUNCE_POOL
static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
{
struct page *page;
struct backing_dev_info *bdi;
struct address_space *mapping;
struct bio_vec *from;
int i;
if (bio_data_dir(bio) != WRITE)
return 0;
if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
return 0;
/*
* Based on the first page that has a valid mapping, decide whether or
* not we have to employ bounce buffering to guarantee stable pages.
*/
bio_for_each_segment(from, bio, i) {
page = from->bv_page;
mapping = page_mapping(page);
if (!mapping)
continue;
bdi = mapping->backing_dev_info;
return mapping->host->i_sb->s_flags & MS_SNAP_STABLE;
}
return 0;
return test_bit(BIO_SNAP_STABLE, &bio->bi_flags);
}
#else
static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)

4
mm/page-writeback.c
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@ -2311,10 +2311,6 @@ void wait_for_stable_page(struct page *page)
if (!bdi_cap_stable_pages_required(bdi))
return;
#ifdef CONFIG_NEED_BOUNCE_POOL
if (mapping->host->i_sb->s_flags & MS_SNAP_STABLE)
return;
#endif /* CONFIG_NEED_BOUNCE_POOL */
wait_on_page_writeback(page);
}