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* vfs: Rename fsync_super() to sync_filesystem() (version 4)Jan Kara2009-06-125-13/+12
| | | | | | | | Rename the function so that it better describe what it really does. Also remove the unnecessary include of buffer_head.h. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: Move syncing code from super.c to sync.c (version 4)Jan Kara2009-06-123-87/+86
| | | | | | | | | | Move sync_filesystems(), __fsync_super(), fsync_super() from super.c to sync.c where it fits better. [build fixes folded] Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: Make sys_sync() use fsync_super() (version 4)Jan Kara2009-06-127-135/+51
| | | | | | | | | | | | | | | | | | It is unnecessarily fragile to have two places (fsync_super() and do_sync()) doing data integrity sync of the filesystem. Alter __fsync_super() to accommodate needs of both callers and use it. So after this patch __fsync_super() is the only place where we gather all the calls needed to properly send all data on a filesystem to disk. Nice bonus is that we get a complete livelock avoidance and write_supers() is now only used for periodic writeback of superblocks. sync_blockdevs() introduced a couple of patches ago is gone now. [build fixes folded] Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: Make __fsync_super() a static function (version 4)Jan Kara2009-06-123-6/+4
| | | | | | | | | | __fsync_super() does the same thing as fsync_super(). So change the only caller to use fsync_super() and make __fsync_super() static. This removes unnecessarily duplicated call to sync_blockdev() and prepares ground for the changes to __fsync_super() in the following patches. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: Call ->sync_fs() even if s_dirt is 0 (version 4)Jan Kara2009-06-121-1/+1
| | | | | | | | | | | sync_filesystems() has a condition that if wait == 0 and s_dirt == 0, then ->sync_fs() isn't called. This does not really make much sence since s_dirt is generally used by a filesystem to mean that ->write_super() needs to be called. But ->sync_fs() does different things. I even suspect that some filesystems (btrfs?) sets s_dirt just to fool this logic. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: Fix sys_sync() and fsync_super() reliability (version 4)Jan Kara2009-06-123-2/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | So far, do_sync() called: sync_inodes(0); sync_supers(); sync_filesystems(0); sync_filesystems(1); sync_inodes(1); This ordering makes it kind of hard for filesystems as sync_inodes(0) need not submit all the IO (for example it skips inodes with I_SYNC set) so e.g. forcing transaction to disk in ->sync_fs() is not really enough. Therefore sys_sync has not been completely reliable on some filesystems (ext3, ext4, reiserfs, ocfs2 and others are hit by this) when racing e.g. with background writeback. A similar problem hits also other filesystems (e.g. ext2) because of write_supers() being called before the sync_inodes(1). Change the ordering of calls in do_sync() - this requires a new function sync_blockdevs() to preserve the property that block devices are always synced after write_super() / sync_fs() call. The same issue is fixed in __fsync_super() function used on umount / remount read-only. [AV: build fixes] Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* remove s_async_listChristoph Hellwig2009-06-122-13/+0
| | | | | | | | | | Remove the unused s_async_list in the superblock, a leftover of the broken async inode deletion code that leaked into mainline. Having this in the middle of the sync/unmount path is not helpful for the following cleanups. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* fs: move mark_files_ro into file_table.cnpiggin@suse.de2009-06-123-39/+43
| | | | | | | | | | | This function walks the s_files lock, and operates primarily on the files in a superblock, so it better belongs here (eg. see also fs_may_remount_ro). [AV: ... and it shouldn't be static after that move] Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* fs: introduce mnt_clone_writenpiggin@suse.de2009-06-126-6/+50
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch speeds up lmbench lat_mmap test by about another 2% after the first patch. Before: avg = 462.286 std = 5.46106 After: avg = 453.12 std = 9.58257 (50 runs of each, stddev gives a reasonable confidence) It does this by introducing mnt_clone_write, which avoids some heavyweight operations of mnt_want_write if called on a vfsmount which we know already has a write count; and mnt_want_write_file, which can call mnt_clone_write if the file is open for write. After these two patches, mnt_want_write and mnt_drop_write go from 7% on the profile down to 1.3% (including mnt_clone_write). [AV: mnt_want_write_file() should take file alone and derive mnt from it; not only all callers have that form, but that's the only mnt about which we know that it's already held for write if file is opened for write] Cc: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* fs: mnt_want_write speedupnpiggin@suse.de2009-06-122-183/+106
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch speeds up lmbench lat_mmap test by about 8%. lat_mmap is set up basically to mmap a 64MB file on tmpfs, fault in its pages, then unmap it. A microbenchmark yes, but it exercises some important paths in the mm. Before: avg = 501.9 std = 14.7773 After: avg = 462.286 std = 5.46106 (50 runs of each, stddev gives a reasonable confidence, but there is quite a bit of variation there still) It does this by removing the complex per-cpu locking and counter-cache and replaces it with a percpu counter in struct vfsmount. This makes the code much simpler, and avoids spinlocks (although the msync is still pretty costly, unfortunately). It results in about 900 bytes smaller code too. It does increase the size of a vfsmount, however. It should also give a speedup on large systems if CPUs are frequently operating on different mounts (because the existing scheme has to operate on an atomic in the struct vfsmount when switching between mounts). But I'm most interested in the single threaded path performance for the moment. [AV: minor cleanup] Cc: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Move junk from proc_fs.h to fs/proc/internal.hAl Viro2009-06-123-24/+26
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch lookup_mnt()Al Viro2009-06-123-6/+6
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch follow_mount()Al Viro2009-06-121-8/+8
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch follow_down()Al Viro2009-06-1212-33/+29
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Switch collect_mounts() to struct pathAl Viro2009-06-123-6/+6
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch follow_up() to struct pathAl Viro2009-06-124-11/+11
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch rqst_exp_parent()Al Viro2009-06-123-28/+23
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch rqst_exp_get_by_name()Al Viro2009-06-123-27/+23
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch exp_parent() to struct pathAl Viro2009-06-121-16/+12
| | | | | | | ... and lose the always-NULL last argument (non-NULL case had been split off a while ago). Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* nfsd struct path use: exp_get_by_name()Al Viro2009-06-121-20/+18
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Don't bother with check_mnt() in do_add_mount() on shrinkable onesAl Viro2009-06-121-1/+1
| | | | | | | | These guys are what we add as submounts; checks for "is that attached in our namespace" are simply irrelevant for those and counterproductive for use of private vfsmount trees a-la what NFS folks want. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Make vfs_path_lookup() use starting point as rootAl Viro2009-06-121-5/+4
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Cache root in nameidataAl Viro2009-06-122-19/+35
| | | | | | | | | | | | New field: nd->root. When pathname resolution wants to know the root, check if nd->root.mnt is non-NULL; use nd->root if it is, otherwise copy current->fs->root there. After path_walk() is finished, we check if we'd got a cached value in nd->root and drop it. Before calling path_walk() we should either set nd->root.mnt to NULL *or* copy (and pin down) some path to nd->root. In the latter case we won't be looking at current->fs->root at all. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Preparations to caching root in path_walk()Al Viro2009-06-121-10/+21
| | | | | | | | | | | Split do_path_lookup(), opencode the call from do_filp_open() do_filp_open() is the only caller of do_path_lookup() that cares about root afterwards (it keeps resolving symlinks on O_CREAT path after it'd done LOOKUP_PARENT walk). So when we start caching fs->root in path_walk(), it'll need a different treatment. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Get rid of path_lookup in autofs4Al Viro2009-06-121-135/+60
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* reiserfs: allow exposing privroot w/ xattrs enabledJeff Mahoney2009-06-124-7/+9
| | | | | | | This patch adds an -oexpose_privroot option to allow access to the privroot. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Merge git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstableLinus Torvalds2009-06-1129-2153/+7306
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable: (23 commits) Btrfs: fix extent_buffer leak during tree log replay Btrfs: fix oops when btrfs_inherit_iflags called with a NULL dir Btrfs: fix -o nodatasum printk spelling Btrfs: check duplicate backrefs for both data and metadata Btrfs: init worker struct fields before kthread-run Btrfs: pin buffers during write_dev_supers Btrfs: avoid races between super writeout and device list updates Fix btrfs when ACLs are configured out Btrfs: fdatasync should skip metadata writeout Btrfs: remove crc32c.h and use libcrc32c directly. Btrfs: implement FS_IOC_GETFLAGS/SETFLAGS/GETVERSION Btrfs: autodetect SSD devices Btrfs: add mount -o ssd_spread to spread allocations out Btrfs: avoid allocation clusters that are too spread out Btrfs: Add mount -o nossd Btrfs: avoid IO stalls behind congested devices in a multi-device FS Btrfs: don't allow WRITE_SYNC bios to starve out regular writes Btrfs: fix metadata dirty throttling limits Btrfs: reduce mount -o ssd CPU usage Btrfs: balance btree more often ...
| * Btrfs: fix extent_buffer leak during tree log replayChris Mason2009-06-111-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | During tree log replay, we read in the tree log roots, process them and then free them. A recent change takes an extra reference on the root node of the tree when the root is read in, and stores that reference in root->commit_root. This reference was not being freed, leaving us with one buffer pinned in ram for each subvol with a tree log root after a crash. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: fix oops when btrfs_inherit_iflags called with a NULL dirChris Mason2009-06-111-1/+6
| | | | | | | | | | | | This happens during subvol creation. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: fix -o nodatasum printk spellingChris Mason2009-06-111-1/+1
| | | | | | | | | | | | It was printing nodatacsum, which was not the correct option name. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: check duplicate backrefs for both data and metadataYan Zheng2009-06-111-11/+4
| | | | | | | | | | | | | | | | | | | | | | | | lookup_inline_extent_backref only checks for duplicate backref for data extents. It assumes backrefs for tree block never conflict. This patch makes lookup_inline_extent_backref check for duplicate backrefs for both data and tree block, so that we can detect potential bug earlier. This is a safety check, strictly speaking it is not required. Signed-off-by: Yan Zheng <zheng.yan@oracle.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: init worker struct fields before kthread-runShin Hong2009-06-111-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes a bug which may result race condition between btrfs_start_workers() and worker_loop(). btrfs_start_workers() executed in a parent thread writes on workers->worker and worker_loop() in a child thread reads workers->worker. However, there is no synchronization enforcing the order of two operations. This patch makes btrfs_start_workers() fill workers->worker before it starts a child thread with worker_loop() Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: pin buffers during write_dev_supersHisashi Hifumi2009-06-101-14/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | write_dev_supers is called in sequence. First is it called with wait == 0, which starts IO on all of the super blocks for a given device. Then it is called with wait == 1 to make sure they all reach the disk. It doesn't currently pin the buffers between the two calls, and it also assumes the buffers won't go away between the two calls, leading to an oops if the VM manages to free the buffers in the middle of the sync. This fixes that assumption and updates the code to return an error if things are not up to date when the wait == 1 run is done. Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: avoid races between super writeout and device list updatesChris Mason2009-06-103-2/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On multi-device filesystems, btrfs writes supers to all of the devices before considering a sync complete. There wasn't any additional locking between super writeout and the device list management code because device management was done inside a transaction and super writeout only happened with no transation writers running. With the btrfs fsync log and other async transaction updates, this has been racey for some time. This adds a mutex to protect the device list. The existing volume mutex could not be reused due to transaction lock ordering requirements. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Fix btrfs when ACLs are configured outAl Viro2009-06-102-5/+4
| | | | | | | | | | | | | | | | ... otherwise generic_permission() will allow *anything* for all files you don't own and that have some group permissions. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: fdatasync should skip metadata writeoutHisashi Hifumi2009-06-101-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In btrfs, fdatasync and fsync are identical, but fdatasync should skip committing transaction when inode->i_state is set just I_DIRTY_SYNC and this indicates only atime or/and mtime updates. Following patch improves fdatasync throughput. --file-block-size=4K --file-total-size=16G --file-test-mode=rndwr --file-fsync-mode=fdatasync run Results: -2.6.30-rc8 Test execution summary: total time: 1980.6540s total number of events: 10001 total time taken by event execution: 1192.9804 per-request statistics: min: 0.0000s avg: 0.1193s max: 15.3720s approx. 95 percentile: 0.7257s Threads fairness: events (avg/stddev): 625.0625/151.32 execution time (avg/stddev): 74.5613/9.46 -2.6.30-rc8-patched Test execution summary: total time: 1695.9118s total number of events: 10000 total time taken by event execution: 871.3214 per-request statistics: min: 0.0000s avg: 0.0871s max: 10.4644s approx. 95 percentile: 0.4787s Threads fairness: events (avg/stddev): 625.0000/131.86 execution time (avg/stddev): 54.4576/8.98 Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: remove crc32c.h and use libcrc32c directly.David Woodhouse2009-06-104-37/+7
| | | | | | | | | | | | | | | | | | | | There's no need to preserve this abstraction; it used to let us use hardware crc32c support directly, but libcrc32c is already doing that for us through the crypto API -- so we're already using the Intel crc32c acceleration where appropriate. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: implement FS_IOC_GETFLAGS/SETFLAGS/GETVERSIONChristoph Hellwig2009-06-105-21/+200
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add support for the standard attributes set via chattr and read via lsattr. Currently we store the attributes in the flags value in the btrfs inode, but I wonder whether we should split it into two so that we don't have to keep converting between the two formats. Remove the btrfs_clear_flag/btrfs_set_flag/btrfs_test_flag macros as they were confusing the existing code and got in the way of the new additions. Also add the FS_IOC_GETVERSION ioctl for getting i_generation as it's trivial. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: autodetect SSD devicesChris Mason2009-06-105-0/+24
| | | | | | | | | | | | | | | | | | | | | | During mount, btrfs will check the queue nonrot flag for all the devices found in the FS. If they are all non-rotating, SSD mode is enabled by default. If the FS was mounted with -o nossd, the non-rotating flag is ignored. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: add mount -o ssd_spread to spread allocations outChris Mason2009-06-105-6/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Some SSDs perform best when reusing block numbers often, while others perform much better when clustering strictly allocates big chunks of unused space. The default mount -o ssd will find rough groupings of blocks where there are a bunch of free blocks that might have some allocated blocks mixed in. mount -o ssd_spread will make sure there are no allocated blocks mixed in. It should perform better on lower end SSDs. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: avoid allocation clusters that are too spread outChris Mason2009-06-101-1/+2
| | | | | | | | | | | | | | | | | | In SSD mode for data, and all the time for metadata the allocator will try to find a cluster of nearby blocks for allocations. This commit adds extra checks to make sure that each free block in the cluster is close to the last one. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: Add mount -o nossdChris Mason2009-06-101-2/+7
| | | | | | | | | | | | This allows you to turn off the ssd mode via remount. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: avoid IO stalls behind congested devices in a multi-device FSChris Mason2009-06-101-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The btrfs IO submission threads try to service a bunch of devices with a small number of threads. They do a congestion check to try and avoid waiting on requests for a busy device. The checks make sure we've sent a few requests down to a given device just so that we aren't bouncing between busy devices without actually sending down any IO. The counter used to decide if we can switch to the next device is somewhat overloaded. It is also being used to decide if we've done a good batch of requests between the WRITE_SYNC or regular priority lists. It may get reset to zero often, leaving us hammering on a busy device instead of moving on to another disk. This commit adds a new counter for the number of bios sent while servicing a device. It doesn't get reset or fiddled with. On multi-device filesystems, this fixes IO stalls in streaming write workloads. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: don't allow WRITE_SYNC bios to starve out regular writesChris Mason2009-06-101-7/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Btrfs uses dedicated threads to submit bios when checksumming is on, which allows us to make sure the threads dedicated to checksumming don't get stuck waiting for requests. For each btrfs device, there are two lists of bios. One list is for WRITE_SYNC bios and the other is for regular priority bios. The IO submission threads used to process all of the WRITE_SYNC bios first and then switch to the regular bios. This commit makes sure we don't completely starve the regular bios by rotating between the two lists. WRITE_SYNC bios are still favored 2:1 over the regular bios, and this tries to run in batches to avoid seeking. Benchmarking shows this eliminates stalls during streaming buffered writes on both multi-device and single device filesystems. If the regular bios starve, the system can end up with a large amount of ram pinned down in writeback pages. If we are a little more fair between the two classes, we're able to keep throughput up and make progress on the bulk of our dirty ram. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: fix metadata dirty throttling limitsChris Mason2009-06-101-5/+2
| | | | | | | | | | | | | | | | | | | | | | | | Once a metadata block has been written, it must be recowed, so the btrfs dirty balancing call has a check to make sure a fair amount of metadata was actually dirty before it started writing it back to disk. A previous commit had changed the dirty tracking for metadata without updating the btrfs dirty balancing checks. This commit switches it to use the correct counter. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: reduce mount -o ssd CPU usageChris Mason2009-06-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | The block allocator in SSD mode will try to find groups of free blocks that are close together. This commit makes it loop less on a given group size before bumping it. The end result is that we are less likely to fill small holes in the available free space, but we don't waste as much CPU building the large cluster used by ssd mode. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: balance btree more oftenChris Mason2009-06-101-2/+2
| | | | | | | | | | | | | | | | | | With the new back reference code, the cost of a balance has gone down in terms of the number of back reference updates done. This commit makes us more aggressively balance leaves and nodes as they become less full. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: stop avoiding balancing at the end of the transaction.Chris Mason2009-06-101-7/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the delayed reference code was added, some checks were added to avoid extra balancing while the delayed references were being flushed. This made for less efficient btrees, but it reduced the chances of loops where no forward progress was made because the balances made more delayed ref updates. With the new dead root removal code and the mixed back references, the extent allocation tree is no longer using precise back refs, and the delayed reference updates don't carry the risk of looping forever anymore. So, the balance avoidance is no longer required. Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * Btrfs: Mixed back reference (FORWARD ROLLING FORMAT CHANGE)Yan Zheng2009-06-1020-2043/+6928
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit introduces a new kind of back reference for btrfs metadata. Once a filesystem has been mounted with this commit, IT WILL NO LONGER BE MOUNTABLE BY OLDER KERNELS. When a tree block in subvolume tree is cow'd, the reference counts of all extents it points to are increased by one. At transaction commit time, the old root of the subvolume is recorded in a "dead root" data structure, and the btree it points to is later walked, dropping reference counts and freeing any blocks where the reference count goes to 0. The increments done during cow and decrements done after commit cancel out, and the walk is a very expensive way to go about freeing the blocks that are no longer referenced by the new btree root. This commit reduces the transaction overhead by avoiding the need for dead root records. When a non-shared tree block is cow'd, we free the old block at once, and the new block inherits old block's references. When a tree block with reference count > 1 is cow'd, we increase the reference counts of all extents the new block points to by one, and decrease the old block's reference count by one. This dead tree avoidance code removes the need to modify the reference counts of lower level extents when a non-shared tree block is cow'd. But we still need to update back ref for all pointers in the block. This is because the location of the block is recorded in the back ref item. We can solve this by introducing a new type of back ref. The new back ref provides information about pointer's key, level and in which tree the pointer lives. This information allow us to find the pointer by searching the tree. The shortcoming of the new back ref is that it only works for pointers in tree blocks referenced by their owner trees. This is mostly a problem for snapshots, where resolving one of these fuzzy back references would be O(number_of_snapshots) and quite slow. The solution used here is to use the fuzzy back references in the common case where a given tree block is only referenced by one root, and use the full back references when multiple roots have a reference on a given block. This commit adds per subvolume red-black tree to keep trace of cached inodes. The red-black tree helps the balancing code to find cached inodes whose inode numbers within a given range. This commit improves the balancing code by introducing several data structures to keep the state of balancing. The most important one is the back ref cache. It caches how the upper level tree blocks are referenced. This greatly reduce the overhead of checking back ref. The improved balancing code scales significantly better with a large number of snapshots. This is a very large commit and was written in a number of pieces. But, they depend heavily on the disk format change and were squashed together to make sure git bisect didn't end up in a bad state wrt space balancing or the format change. Signed-off-by: Yan Zheng <zheng.yan@oracle.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
| * btrfs: Fix set/clear_extent_bit for 'end == (u64)-1'Yan Zheng2009-06-101-4/+14
| | | | | | | | | | | | | | | | There are some 'start = state->end + 1;' like code in set_extent_bit and clear_extent_bit. They overflow when end == (u64)-1. Signed-off-by: Yan Zheng <zheng.yan@oracle.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>