kernel.git/fs/nilfs2/segment.c, branch linux-2.6.37.y

nilfs2: fix regression that i-flag is not set on changeless checkpoints

2011-03-07T23:05:25Z

commit 72746ac643928f6c3113b5aa783d8ea1b13949d2 upstream. According to the report from Jiro SEKIBA titled "regression in 2.6.37?" (Message-Id: <8739n8vs1f.wl%jir@sekiba.com>), on 2.6.37 and later kernels, lscp command no longer displays "i" flag on checkpoints that snapshot operations or garbage collection created. This is a regression of nilfs2 checkpointing function, and it's critical since it broke behavior of a part of nilfs2 applications. For instance, snapshot manager of TimeBrowse gets to create meaningless snapshots continuously; snapshot creation triggers another checkpoint, but applications cannot distinguish whether the new checkpoint contains meaningful changes or not without the i-flag. This patch fixes the regression and brings that application behavior back to normal. Reported-by: Jiro SEKIBA Signed-off-by: Ryusuke Konishi Tested-by: Ryusuke Konishi Tested-by: Jiro SEKIBA Signed-off-by: Greg Kroah-Hartman

mm: add account_page_writeback()

2010-10-26T23:52:06Z

To help developers and applications gain visibility into writeback behaviour this patch adds two counters to /proc/vmstat. # grep nr_dirtied /proc/vmstat nr_dirtied 3747 # grep nr_written /proc/vmstat nr_written 3618 These entries allow user apps to understand writeback behaviour over time and learn how it is impacting their performance. Currently there is no way to inspect dirty and writeback speed over time. It's not possible for nr_dirty/nr_writeback. These entries are necessary to give visibility into writeback behaviour. We have /proc/diskstats which lets us understand the io in the block layer. We have blktrace for more in depth understanding. We have e2fsprogs and debugsfs to give insight into the file systems behaviour, but we don't offer our users the ability understand what writeback is doing. There is no way to know how active it is over the whole system, if it's falling behind or to quantify it's efforts. With these values exported users can easily see how much data applications are sending through writeback and also at what rates writeback is processing this data. Comparing the rates of change between the two allow developers to see when writeback is not able to keep up with incoming traffic and the rate of dirty memory being sent to the IO back end. This allows folks to understand their io workloads and track kernel issues. Non kernel engineers at Google often use these counters to solve puzzling performance problems. Patch #4 adds a pernode vmstat file with nr_dirtied and nr_written Patch #5 add writeback thresholds to /proc/vmstat Currently these values are in debugfs. But they should be promoted to /proc since they are useful for developers who are writing databases and file servers and are not debugging the kernel. The output is as below: # grep threshold /proc/vmstat nr_pages_dirty_threshold 409111 nr_pages_dirty_background_threshold 818223 This patch: This allows code outside of the mm core to safely manipulate page writeback state and not worry about the other accounting. Not using these routines means that some code will lose track of the accounting and we get bugs. Modify nilfs2 to use interface. Signed-off-by: Michael Rubin Reviewed-by: KOSAKI Motohiro Reviewed-by: Wu Fengguang Cc: KONISHI Ryusuke Cc: Jiro SEKIBA Cc: Dave Chinner Cc: Jens Axboe Cc: KOSAKI Motohiro Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

nilfs2: eliminate sparse warning - "context imbalance"

2010-10-23T00:24:40Z

insert sparse annotations to fix following sparse warning. fs/nilfs2/segment.c:2681:3: warning: context imbalance in 'nilfs_segctor_kill_thread' - unexpected unlock nilfs_segctor_kill_thread is only called inside sc_state_lock lock. sparse doesn't detect the context and warn "unexpected unlock". __acquires/__releases pretend to lock/unlock the sc_state_lock for sparse. Signed-off-by: Jiro SEKIBA Signed-off-by: Ryusuke Konishi

nilfs2: add bdev freeze/thaw support

2010-10-23T00:24:39Z

Nilfs hasn't supported the freeze/thaw feature because it didn't work due to the peculiar design that multiple super block instances could be allocated for a device. This limitation was removed by the patch "nilfs2: do not allocate multiple super block instances for a device". So now this adds the freeze/thaw support to nilfs. Signed-off-by: Ryusuke Konishi

nilfs2: get rid of back pointer to writable sb instance

2010-10-23T00:24:38Z

Nilfs object holds a back pointer to a writable super block instance in nilfs->ns_writer, and this became eliminable since sb is now made per device and all inodes have a valid pointer to it. This deletes the ns_writer pointer and a reader/writer semaphore protecting it. Signed-off-by: Ryusuke Konishi

nilfs2: get rid of GCDAT inode

2010-10-23T00:24:38Z

This applies prepared rollback function and redirect function of metadata file to DAT file, and eliminates GCDAT inode. Signed-off-by: Ryusuke Konishi

nilfs2: add routines to redirect access to buffers of DAT file

2010-10-23T00:24:37Z

During garbage collection (GC), DAT file, which converts virtual block number to real block number, may return disk block number that is not yet written to the device. To avoid access to unwritten blocks, the current implementation stores changes to the caches of GCDAT during GC and atomically commit the changes into the DAT file after they are written to the device. This patch, instead, adds a function that makes a copy of specified buffer and stores it in nilfs_shadow_map, and a function to get the backup copy as needed (nilfs_mdt_freeze_buffer and nilfs_mdt_get_frozen_buffer respectively). Before DAT changes block number in an entry block, it makes a copy and redirect access to the buffer so that address conversion function (i.e. nilfs_dat_translate) refers to the old address saved in the copy. This patch gives requisites for such redirection. Signed-off-by: Ryusuke Konishi

nilfs2: move inode count and block count into root object

2010-10-23T00:24:35Z

This moves sbi->s_inodes_count and sbi->s_blocks_count into nilfs_root object. Signed-off-by: Ryusuke Konishi

nilfs2: use root object to get ifile

2010-10-23T00:24:35Z

This rewrites functions using ifile so that they get ifile from nilfs_root object, and will remove sbi->s_ifile. Some functions that don't know the root object are extended to receive it from caller. Signed-off-by: Ryusuke Konishi

nilfs2: remove own inode hash used for GC

2010-10-23T00:24:34Z

This uses inode hash function that vfs provides instead of the own hash table for caching gc inodes. This finally removes the own inode hash from nilfs. Signed-off-by: Ryusuke Konishi