linux/fs/fs-writeback.c, branch v3.0

fs: pass exact type of data dirties to ->dirty_inode

2011-05-27T11:04:40Z

Tell the filesystem if we just updated timestamp (I_DIRTY_SYNC) or anything else, so that the filesystem can track internally if it needs to push out a transaction for fdatasync or not. This is just the prototype change with no user for it yet. I plan to push large XFS changes for the next merge window, and getting this trivial infrastructure in this window would help a lot to avoid tree interdependencies. Also remove incorrect comments that ->dirty_inode can't block. That has been changed a long time ago, and many implementations rely on it. Signed-off-by: Christoph Hellwig Signed-off-by: Al Viro

Fix common misspellings

2011-03-31T14:26:23Z

Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi

fs: pull inode->i_lock up out of writeback_single_inode

2011-03-25T01:17:51Z

First thing we do in writeback_single_inode() is take the i_lock and the last thing we do is drop it. A caller already holds the i_lock, so pull the i_lock out of writeback_single_inode() to reduce the round trips on this lock during inode writeback. Signed-off-by: Dave Chinner Signed-off-by: Al Viro

fs: move i_wb_list out from under inode_lock

2011-03-25T01:17:51Z

Protect the inode writeback list with a new global lock inode_wb_list_lock and use it to protect the list manipulations and traversals. This lock replaces the inode_lock as the inodes on the list can be validity checked while holding the inode->i_lock and hence the inode_lock is no longer needed to protect the list. Signed-off-by: Dave Chinner Signed-off-by: Al Viro

fs: move i_sb_list out from under inode_lock

2011-03-25T01:16:32Z

Protect the per-sb inode list with a new global lock inode_sb_list_lock and use it to protect the list manipulations and traversals. This lock replaces the inode_lock as the inodes on the list can be validity checked while holding the inode->i_lock and hence the inode_lock is no longer needed to protect the list. Signed-off-by: Dave Chinner Signed-off-by: Al Viro

fs: protect inode->i_state with inode->i_lock

2011-03-25T01:16:31Z

Protect inode state transitions and validity checks with the inode->i_lock. This enables us to make inode state transitions independently of the inode_lock and is the first step to peeling away the inode_lock from the code. This requires that __iget() is done atomically with i_state checks during list traversals so that we don't race with another thread marking the inode I_FREEING between the state check and grabbing the reference. Also remove the unlock_new_inode() memory barrier optimisation required to avoid taking the inode_lock when clearing I_NEW. Simplify the code by simply taking the inode->i_lock around the state change and wakeup. Because the wakeup is no longer tricky, remove the wake_up_inode() function and open code the wakeup where necessary. Signed-off-by: Dave Chinner Signed-off-by: Al Viro

fs/fs-writeback.c: fix sync_inodes_sb() return value kernel-doc

2011-01-14T01:32:48Z

The sync_inodes_sb() function does not have a return value. Remove the outdated documentation comment. Signed-off-by: Stefan Hajnoczi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sync_inode_metadata: fix comment

2011-01-14T01:32:32Z

Use correct function name, remove incorrect apostrophe Cc: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

writeback: avoid livelocking WB_SYNC_ALL writeback

2011-01-14T01:32:32Z

When wb_writeback() is called in WB_SYNC_ALL mode, work->nr_to_write is usually set to LONG_MAX. The logic in wb_writeback() then calls __writeback_inodes_sb() with nr_to_write == MAX_WRITEBACK_PAGES and we easily end up with non-positive nr_to_write after the function returns, if the inode has more than MAX_WRITEBACK_PAGES dirty pages at the moment. When nr_to_write is <= 0 wb_writeback() decides we need another round of writeback but this is wrong in some cases! For example when a single large file is continuously dirtied, we would never finish syncing it because each pass would be able to write MAX_WRITEBACK_PAGES and inode dirty timestamp never gets updated (as inode is never completely clean). Thus __writeback_inodes_sb() would write the redirtied inode again and again. Fix the issue by setting nr_to_write to LONG_MAX in WB_SYNC_ALL mode. We do not need nr_to_write in WB_SYNC_ALL mode anyway since write_cache_pages() does livelock avoidance using page tagging in WB_SYNC_ALL mode. This makes wb_writeback() call __writeback_inodes_sb() only once on WB_SYNC_ALL. The latter function won't livelock because it works on - a finite set of files by doing queue_io() once at the beginning - a finite set of pages by PAGECACHE_TAG_TOWRITE page tagging After this patch, program from http://lkml.org/lkml/2010/10/24/154 is no longer able to stall sync forever. [fengguang.wu@intel.com: fix locking comment] Signed-off-by: Jan Kara Signed-off-by: Wu Fengguang Cc: Johannes Weiner Cc: Dave Chinner Cc: Christoph Hellwig Cc: Jan Engelhardt Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

writeback: stop background/kupdate works from livelocking other works

2011-01-14T01:32:32Z

Background writeback is easily livelockable in a loop in wb_writeback() by a process continuously re-dirtying pages (or continuously appending to a file). This is in fact intended as the target of background writeback is to write dirty pages it can find as long as we are over dirty_background_threshold. But the above behavior gets inconvenient at times because no other work queued in the flusher thread's queue gets processed. In particular, since e.g. sync(1) relies on flusher thread to do all the IO for it, sync(1) can hang forever waiting for flusher thread to do the work. Generally, when a flusher thread has some work queued, someone submitted the work to achieve a goal more specific than what background writeback does. Moreover by working on the specific work, we also reduce amount of dirty pages which is exactly the target of background writeout. So it makes sense to give specific work a priority over a generic page cleaning. Thus we interrupt background writeback if there is some other work to do. We return to the background writeback after completing all the queued work. This may delay the writeback of expired inodes for a while, however the expired inodes will eventually be flushed to disk as long as the other works won't livelock. [fengguang.wu@intel.com: update comment] Signed-off-by: Jan Kara Signed-off-by: Wu Fengguang Cc: Johannes Weiner Cc: Dave Chinner Cc: Christoph Hellwig Cc: Jan Engelhardt Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds