BMC/Intel-BMC/linux.git/fs/gfs2/log.h, branch dev

GFS2: remove transaction glock

2014-05-14T09:04:34+00:00

GFS2 has a transaction glock, which must be grabbed for every transaction, whose purpose is to deal with freezing the filesystem. Aside from this involving a large amount of locking, it is very easy to make the current fsfreeze code hang on unfreezing. This patch rewrites how gfs2 handles freezing the filesystem. The transaction glock is removed. In it's place is a freeze glock, which is cached (but not held) in a shared state by every node in the cluster when the filesystem is mounted. This lock only needs to be grabbed on freezing, and actions which need to be safe from freezing, like recovery. When a node wants to freeze the filesystem, it grabs this glock exclusively. When the freeze glock state changes on the nodes (either from shared to unlocked, or shared to exclusive), the filesystem does a special log flush. gfs2_log_flush() does all the work for flushing out the and shutting down the incore log, and then it tries to grab the freeze glock in a shared state again. Since the filesystem is stuck in gfs2_log_flush, no new transaction can start, and nothing can be written to disk. Unfreezing the filesytem simply involes dropping the freeze glock, allowing gfs2_log_flush() to grab and then release the shared lock, so it is cached for next time. However, in order for the unfreezing ioctl to occur, gfs2 needs to get a shared lock on the filesystem root directory inode to check permissions. If that glock has already been grabbed exclusively, fsfreeze will be unable to get the shared lock and unfreeze the filesystem. In order to allow the unfreeze, this patch makes gfs2 grab a shared lock on the filesystem root directory during the freeze, and hold it until it unfreezes the filesystem. The functions which need to grab a shared lock in order to allow the unfreeze ioctl to be issued now use the lock grabbed by the freeze code instead. The freeze and unfreeze code take care to make sure that this shared lock will not be dropped while another process is using it. Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse

GFS2: aggressively issue revokes in gfs2_log_flush

2013-06-19T08:41:59+00:00

This patch looks at all the outstanding blocks in all the transactions on the log, and moves the completed ones to the ail2 list. Then it issues revokes for these blocks. This will hopefully speed things up in situations where there is a lot of contention for glocks, especially if they are acquired serially. revoke_lo_before_commit will issue at most one log block's full of these preemptive revokes. The amount of reserved log space that gfs2_log_reserve() ignores has been incremented to allow for this extra block. This patch also consolidates the common revoke instructions into one function, gfs2_add_revoke(). Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse

GFS2: Use ->writepages for ordered writes

2013-01-29T10:29:17+00:00

Instead of using a list of buffers to write ahead of the journal flush, this now uses a list of inodes and calls ->writepages via filemap_fdatawrite() in order to achieve the same thing. For most use cases this results in a shorter ordered write list, as well as much larger i/os being issued. The ordered write list is sorted by inode number before writing in order to retain the disk block ordering between inodes as per the previous code. The previous ordered write code used to conflict in its assumptions about how to write out the disk blocks with mpage_writepages() so that with this updated version we can also use mpage_writepages() for GFS2's ordered write, writepages implementation. So we will also send larger i/os from writeback too. Signed-off-by: Steven Whitehouse

GFS2: Clean up log write code path

2012-04-24T15:44:34+00:00

Prior to this patch, we have two ways of sending i/o to the log. One of those is used when we need to allocate both the data to be written itself and also a buffer head to submit it. This is done via sb_getblk and friends. This is used mostly for writing log headers. The other method is used when writing blocks which have some in-place counterpart. This is the case for all the metadata blocks which are journalled, and when journaled data is in use, for unescaped journalled data blocks. This patch replaces both of those two methods, and about half a dozen separate i/o submission points with a single i/o submission function. We also go direct to bio rather than using buffer heads, since this allows us to build i/o requests of the maximum size for the block device in question. It also reduces the memory required for flushing the log, which can be very useful in low memory situations. Signed-off-by: Steven Whitehouse

GFS2: Move two functions from log.c to lops.c

2012-02-28T17:09:59+00:00

gfs2_log_get_buf() and gfs2_log_fake_buf() are both used only in lops.c, so move them next to their callers and they can then become static. Signed-off-by: Steven Whitehouse

GFS2: Make writeback more responsive to system conditions

2011-04-20T08:01:37+00:00

This patch adds writeback_control to writing back the AIL list. This means that we can then take advantage of the information we get in ->write_inode() in order to set off some pre-emptive writeback. In addition, the AIL code is cleaned up a bit to make it a bit simpler to understand. There is still more which can usefully be done in this area, but this is a good start at least. Signed-off-by: Steven Whitehouse

GFS2: Rework reclaiming unlinked dinodes

2010-05-21T15:11:36+00:00

The previous patch I wrote for reclaiming unlinked dinodes had some shortcomings and did not prevent all hangs. This version is much cleaner and more logical, and has passed very difficult testing. Sorry for the churn. Signed-off-by: Bob Peterson Signed-off-by: Steven Whitehouse

GFS2: Various gfs2_logd improvements

2010-05-05T08:39:18+00:00

This patch contains various tweaks to how log flushes and active item writeback work. gfs2_logd is now managed by a waitqueue, and gfs2_log_reseve now waits for gfs2_logd to do the log flushing. Multiple functions were rewritten to remove the need to call gfs2_log_lock(). Instead of using one test to see if gfs2_logd had work to do, there are now seperate tests to check if there are two many buffers in the incore log or if there are two many items on the active items list. This patch is a port of a patch Steve Whitehouse wrote about a year ago, with some minor changes. Since gfs2_ail1_start always submits all the active items, it no longer needs to keep track of the first ai submitted, so this has been removed. In gfs2_log_reserve(), the order of the calls to prepare_to_wait_exclusive() and wake_up() when firing off the logd thread has been switched. If it called wake_up first there was a small window for a race, where logd could run and return before gfs2_log_reserve was ready to get woken up. If gfs2_logd ran, but did not free up enough blocks, gfs2_log_reserve() would be left waiting for gfs2_logd to eventualy run because it timed out. Finally, gt_logd_secs, which controls how long to wait before gfs2_logd times out, and flushes the log, can now be set on mount with ar_commit. Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse

[GFS2] trivial sparse lock annotations

2008-06-27T08:39:31+00:00

Annotate the &sdp->sd_log_lock. Signed-off-by: Harvey Harrison Signed-off-by: Steven Whitehouse

[GFS2] Move gfs2_logd into log.c

2008-01-25T08:07:56+00:00

This means that we can mark gfs2_ail1_empty static and prepares the way for further changes. Signed-off-by: Steven Whitehouse