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.
[[email protected]: rename _submit_bh()'s `flags' to `bio_flags', delobotomize the _submit_bh declaration]
[[email protected]: teeny cleanup]
Signed-off-by: Darrick J. Wong <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Artem Bityutskiy <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Cc: Jens Axboe <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This provides a band-aid to provide stable page writes on jbd without
needing to backport the fixed locking and page writeback bit handling
schemes of jbd2. The band-aid works by using bounce buffers to snapshot
page contents instead of waiting.
For those wondering about the ext3 bandage -- fixing the jbd locking
(which was done as part of ext4dev years ago) is a lot of surgery, and
setting PG_writeback on data pages when we actually hold the page lock
dropped ext3 performance by nearly an order of magnitude. If we're
going to migrate iscsi and raid to use stable page writes, the
complaints about high latency will likely return. We might as well
centralize their page snapshotting thing to one place.
Signed-off-by: Darrick J. Wong <[email protected]>
Tested-by: Andy Lutomirski <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Artem Bityutskiy <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Steven Whitehouse <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Eric Van Hensbergen <[email protected]>
Cc: Ron Minnich <[email protected]>
Cc: Latchesar Ionkov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
There are some bits of linux/fs.h which are only used within the kernel and
shouldn't be in the UAPI. Move these from uapi/linux/fs.h into linux/fs.h.
Signed-off-by: David Howells <[email protected]>
Signed-off-by: Al Viro <[email protected]>
Darrick J. Wong