[PATCH] mm: Make snapshotting pages for stable writes a per-bio operation
Darrick J. Wong
darrick.wong at oracle.com
Fri Mar 15 19:28:16 EDT 2013
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 if data=journal, since file data is written
through the journal. Finally, the MS_SNAP_STABLE mount flag (only used by
ext3) is now superfluous, so get rid of it.
Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
[darrick.wong at oracle.com: Fold in a couple of small cleanups from akpm]
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
fs/buffer.c | 9 ++++++++-
fs/ext3/super.c | 3 ++-
fs/jbd/commit.c | 28 +++++++++++++++++++++++++---
include/linux/blk_types.h | 3 ++-
include/linux/buffer_head.h | 1 +
include/linux/jbd.h | 1 +
include/uapi/linux/fs.h | 1 -
mm/bounce.c | 21 +--------------------
mm/page-writeback.c | 4 ----
9 files changed, 40 insertions(+), 31 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index b4dcb34..71578d6 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -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);
/**
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 1d6e2ed..e845b6de 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -2063,11 +2063,12 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
ext3_mark_recovery_complete(sb, es);
ext3_msg(sb, KERN_INFO, "recovery complete");
}
+ if (test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_JOURNAL_DATA)
+ EXT3_SB(sb)->s_journal->j_flags |= JFS_JOURNALS_DATA;
ext3_msg(sb, KERN_INFO, "mounted filesystem with %s data mode",
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;
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 86b39b1..37a60dd 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -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);
}
}
@@ -663,11 +672,24 @@ void journal_commit_transaction(journal_t *journal)
start_journal_io:
for (i = 0; i < bufs; i++) {
struct buffer_head *bh = wbuf[i];
+ unsigned long bio_flags = 0;
lock_buffer(bh);
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.
+ */
+ if (journal->j_flags & JFS_JOURNALS_DATA)
+ bio_flags = 1 << BIO_SNAP_STABLE;
+ _submit_bh(write_op, bh, bio_flags);
}
cond_resched();
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index cdf1119..22990cf 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -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)))
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 5afc4f9..4c16c4a 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -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);
diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index c8f3297..2bfd613 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -768,6 +768,7 @@ struct journal_s
#define JFS_ABORT_ON_SYNCDATA_ERR 0x040 /* Abort the journal on file
* data write error in ordered
* mode */
+#define JFS_JOURNALS_DATA 0x080 /* data=journal mode */
/*
* Function declarations for the journaling transaction and buffer
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index c7fc1e6..a4ed56c 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -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)
diff --git a/mm/bounce.c b/mm/bounce.c
index 5f89017..a5c2ec3 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -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)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index efe6814..4514ad7 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -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);
}
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