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path: root/fs/btrfs/disk-io.c
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* btrfs: get rid of current_is_pdflush() in btrfs_btree_balance_dirtyJens Axboe2009-03-26
| | | | | | | Chris says it's safe to kill. Acked-by: Chris Mason <chris.mason@oracle.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* Btrfs: fix spinlock assertions on UP systemsChris Mason2009-03-09
| | | | | | | | | | | btrfs_tree_locked was being used to make sure a given extent_buffer was properly locked in a few places. But, it wasn't correct for UP compiled kernels. This switches it to using assert_spin_locked instead, and renames it to btrfs_assert_tree_locked to better reflect how it was really being used. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: make a lockdep class for the extent buffer locksChris Mason2009-02-12
| | | | | | | | | | | | | | | | | | | | Btrfs is currently using spin_lock_nested with a nested value based on the tree depth of the block. But, this doesn't quite work because the max tree depth is bigger than what spin_lock_nested can deal with, and because locks are sometimes taken before the level field is filled in. The solution here is to use lockdep_set_class_and_name instead, and to set the class before unlocking the pages when the block is read from the disk and just after init of a freshly allocated tree block. btrfs_clear_path_blocking is also changed to take the locks in the proper order, and it also makes sure all the locks currently held are properly set to blocking before it tries to retake the spinlocks. Otherwise, lockdep gets upset about bad lock orderin. The lockdep magic cam from Peter Zijlstra <peterz@infradead.org> Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Change btree locking to use explicit blocking pointsChris Mason2009-02-04
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Most of the btrfs metadata operations can be protected by a spinlock, but some operations still need to schedule. So far, btrfs has been using a mutex along with a trylock loop, most of the time it is able to avoid going for the full mutex, so the trylock loop is a big performance gain. This commit is step one for getting rid of the blocking locks entirely. btrfs_tree_lock takes a spinlock, and the code explicitly switches to a blocking lock when it starts an operation that can schedule. We'll be able get rid of the blocking locks in smaller pieces over time. Tracing allows us to find the most common cause of blocking, so we can start with the hot spots first. The basic idea is: btrfs_tree_lock() returns with the spin lock held btrfs_set_lock_blocking() sets the EXTENT_BUFFER_BLOCKING bit in the extent buffer flags, and then drops the spin lock. The buffer is still considered locked by all of the btrfs code. If btrfs_tree_lock gets the spinlock but finds the blocking bit set, it drops the spin lock and waits on a wait queue for the blocking bit to go away. Much of the code that needs to set the blocking bit finishes without actually blocking a good percentage of the time. So, an adaptive spin is still used against the blocking bit to avoid very high context switch rates. btrfs_clear_lock_blocking() clears the blocking bit and returns with the spinlock held again. btrfs_tree_unlock() can be called on either blocking or spinning locks, it does the right thing based on the blocking bit. ctree.c has a helper function to set/clear all the locked buffers in a path as blocking. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: hash_lock is no longer neededChris Mason2009-02-04
| | | | | | | | | | | | | | | Before metadata is written to disk, it is updated to reflect that writeout has begun. Once this update is done, the block must be cow'd before it can be modified again. This update was originally synchronized by using a per-fs spinlock. Today the buffers for the metadata blocks are locked before writeout begins, and everyone that tests the flag has the buffer locked as well. So, the per-fs spinlock (called hash_lock for no good reason) is no longer required. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: async threads should try harder to find workChris Mason2009-02-04
| | | | | | | | | | | | Tracing shows the delay between when an async thread goes to sleep and when more work is added is often very short. This commit adds a little bit of delay and extra checking to the code right before we schedule out. It allows more work to be added to the worker without requiring notifications from other procs. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: fix tree logs parallel syncYan Zheng2009-01-21
| | | | | | | | | | | | | | | | | | | | | | | | | | To improve performance, btrfs_sync_log merges tree log sync requests. But it wrongly merges sync requests for different tree logs. If multiple tree logs are synced at the same time, only one of them actually gets synced. This patch has following changes to fix the bug: Move most tree log related fields in btrfs_fs_info to btrfs_root. This allows merging sync requests separately for each tree log. Don't insert root item into the log root tree immediately after log tree is allocated. Root item for log tree is inserted when log tree get synced for the first time. This allows syncing the log root tree without first syncing all log trees. At tree-log sync, btrfs_sync_log first sync the log tree; then updates corresponding root item in the log root tree; sync the log root tree; then update the super block. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: open_ctree() error handling can oops on fs_infoQinghuang Feng2009-01-21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | a bug in open_ctree: struct btrfs_root *open_ctree(..) { .... if (!extent_root || !tree_root || !fs_info || !chunk_root || !dev_root || !csum_root) { err = -ENOMEM; goto fail; //When code flow goes to "fail", fs_info may be NULL or uninitialized. } .... fail: btrfs_close_devices(fs_info->fs_devices);// ! btrfs_mapping_tree_free(&fs_info->mapping_tree);// ! kfree(extent_root); kfree(tree_root); bdi_destroy(&fs_info->bdi);// ! ... ) Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: simplify iteration codesQinghuang Feng2009-01-21
| | | | | | | | Merge list_for_each* and list_entry to list_for_each_entry* Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: check return value for kthread_run() correctlyQinghuang Feng2009-01-21
| | | | | | | | kthread_run() returns the kthread or ERR_PTR(-ENOMEM), not NULL. Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: removed unused #include <version.h>'sHuang Weiyi2009-01-21
| | | | | | | | Removed unused #include <version.h>'s in btrfs Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Fix checkpatch.pl warningsChris Mason2009-01-05
| | | | | | | There were many, most are fixed now. struct-funcs.c generates some warnings but these are bogus. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: avoid potential super block corruptionYan Zheng2009-01-05
| | | | | | | | | | | | | The data in fs_info->super_for_commit are zeros before the first transaction commit. If tree log sync and system crash both occur before the first transaction commit, super block will get corrupted. This fixes it by properly filling in the super_for_commit field at open time. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: Fix compile warning around num_online_cpus() in a min statementChris Mason2008-12-19
| | | | Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: shift all end_io work to thread poolsChris Mason2008-12-17
| | | | | | | | | | | | | | | | | | bio_end_io for reads without checksumming on and btree writes were happening without using async thread pools. This means the extent_io.c code had to use spin_lock_irq and friends on the rb tree locks for extent state. There were some irq safe vs unsafe lock inversions between the delallock lock and the extent state locks. This patch gets rid of them by moving all end_io code into the thread pools. To avoid contention and deadlocks between the data end_io processing and the metadata end_io processing yet another thread pool is added to finish off metadata writes. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: shared seed deviceYan Zheng2008-12-12
| | | | | | | | | | This patch makes seed device possible to be shared by multiple mounted file systems. The sharing is achieved by cloning seed device's btrfs_fs_devices structure. Thanks you, Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: Add checking of csum tree in balancing codeYan Zheng2008-12-10
| | | | | | | | This updates the space balancing code for the new checksum format. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: superblock duplicationYan Zheng2008-12-08
| | | | | | | | | | | This patch implements superblock duplication. Superblocks are stored at offset 16K, 64M and 256G on every devices. Spaces used by superblocks are preserved by the allocator, which uses a reverse mapping function to find the logical addresses that correspond to superblocks. Thank you, Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: move data checksumming into a dedicated treeChris Mason2008-12-08
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Btrfs stores checksums for each data block. Until now, they have been stored in the subvolume trees, indexed by the inode that is referencing the data block. This means that when we read the inode, we've probably read in at least some checksums as well. But, this has a few problems: * The checksums are indexed by logical offset in the file. When compression is on, this means we have to do the expensive checksumming on the uncompressed data. It would be faster if we could checksum the compressed data instead. * If we implement encryption, we'll be checksumming the plain text and storing that on disk. This is significantly less secure. * For either compression or encryption, we have to get the plain text back before we can verify the checksum as correct. This makes the raid layer balancing and extent moving much more expensive. * It makes the front end caching code more complex, as we have touch the subvolume and inodes as we cache extents. * There is potentitally one copy of the checksum in each subvolume referencing an extent. The solution used here is to store the extent checksums in a dedicated tree. This allows us to index the checksums by phyiscal extent start and length. It means: * The checksum is against the data stored on disk, after any compression or encryption is done. * The checksum is stored in a central location, and can be verified without following back references, or reading inodes. This makes compression significantly faster by reducing the amount of data that needs to be checksummed. It will also allow much faster raid management code in general. The checksums are indexed by a key with a fixed objectid (a magic value in ctree.h) and offset set to the starting byte of the extent. This allows us to copy the checksum items into the fsync log tree directly (or any other tree), without having to invent a second format for them. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: add support for multiple csum algorithmsJosef Bacik2008-12-02
| | | | | | | | | This patch gives us the space we will need in order to have different csum algorithims at some point in the future. We save the csum algorithim type in the superblock, and use those instead of define's. Signed-off-by: Josef Bacik <jbacik@redhat.com>
* Btrfs: fix panic on error during mountJosef Bacik2008-12-02
| | | | | | | | | | | This needs to be applied on top of my previous patches, but is needed for more than just my new stuff. We're going to the wrong label when we have an error, we try to stop the workers, but they are started below all of this code. This fixes it so we go to the right error label and not panic when we fail one of these cases. Signed-off-by: Josef Bacik <jbacik@redhat.com>
* Btrfs: add support for compat flags to btrfsJosef Bacik2008-12-02
| | | | | | | | | | | | | | | | This adds the necessary disk format for handling compatibility flags in the future to handle disk format changes. We have a compat_flags, compat_ro_flags and incompat_flags set for the super block. Compat flags will be to hold the features that are compatible with older versions of btrfs, compat_ro flags have features that are compatible with older versions of btrfs if the fs is mounted read only, and incompat_flags has features that are incompatible with older versions of btrfs. This also axes the compat_flags field for the inode and just makes the flags field a 64bit field, and changes the root item flags field to 64bit. Signed-off-by: Josef Bacik <jbacik@redhat.com>
* Btrfs: fix shadowed variable declarationsChristoph Hellwig2008-12-02
| | | | | Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: make things static and include the right headersChristoph Hellwig2008-12-02
| | | | | | | | Shut up various sparse warnings about symbols that should be either static or have their declarations in scope. Signed-off-by: Christoph Hellwig <hch@lst.de>
* Btrfs: Drop dirty roots created by log replay immediately whenYan Zheng2008-11-20
| | | | | | | | | | The log replay produces dirty roots. These dirty roots should be dropped immediately if the fs is mounted as ro. Otherwise they can be added to the dirty root list again when remounting the fs as rw. Thank you, Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: compat code fixesChris Mason2008-11-20
| | | | | | | | The btrfs git kernel trees is used to build a standalone tree for compiling against older kernels. This commit makes the standalone tree work with 2.6.27 Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Do fsync log replay when mount -o ro, except when on readonly mediaChris Mason2008-11-19
| | | | | | | | | | | | | | fsync log replay can change the filesystem, so it cannot be delayed until mount -o rw,remount, and it can't be forgotten entirely. So, this patch changes btrfs to do with reiserfs, ext3 and xfs do, which is to do the log replay even when mounted readonly. On a readonly device if log replay is required, the mount is aborted. Getting all of this right had required fixing up some of the error handling in open_ctree. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Avoid writeback stallsChris Mason2008-11-19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | While building large bios in writepages, btrfs may end up waiting for other page writeback to finish if WB_SYNC_ALL is used. While it is waiting, the bio it is building has a number of pages with the writeback bit set and they aren't getting to the disk any time soon. This lowers the latencies of writeback in general by sending down the bio being built before waiting for other pages. The bio submission code tries to limit the total number of async bios in flight by waiting when we're over a certain number of async bios. But, the waits are happening while writepages is building bios, and this can easily lead to stalls and other problems for people calling wait_on_page_writeback. The current fix is to let the congestion tests take care of waiting. sync() and others make sure to drain the current async requests to make sure that everything that was pending when the sync was started really get to disk. The code would drain pending requests both before and after submitting a new request. But, if one of the requests is waiting for page writeback to finish, the draining waits might block that page writeback. This changes the draining code to only wait after submitting the bio being processed. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: unplug all devices in the unplug call backChris Mason2008-11-18
| | | | | | | | | | | | For larger multi-device filesystems, there was logic to limit the number of devices unplugged to just the page that was sent to our sync_page function. But, the code wasn't always unplugging the right device. Since this was just an optimization, disable it for now. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: prevent loops in the directory tree when creating snapshotsChris Mason2008-11-17
| | | | | | | | | | | | | | | For a directory tree: /mnt/subvolA/subvolB btrfsctl -s /mnt/subvolA/subvolB /mnt Will create a directory loop with subvolA under subvolB. This commit uses the forward refs for each subvol and snapshot to error out before creating the loop. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Give each subvol and snapshot their own anonymous devidChris Mason2008-11-17
| | | | | | | | | | | | | | Each subvolume has its own private inode number space, and so we need to fill in different device numbers for each subvolume to avoid confusing applications. This commit puts a struct super_block into struct btrfs_root so it can call set_anon_super() and get a different device number generated for each root. btrfs_rename is changed to prevent renames across subvols. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Allow subvolumes and snapshots anywhere in the directory treeChris Mason2008-11-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Before, all snapshots and subvolumes lived in a single flat directory. This was awkward and confusing because the single flat directory was only writable with the ioctls. This commit changes the ioctls to create subvols and snapshots at any point in the directory tree. This requires making separate ioctls for snapshot and subvol creation instead of a combining them into one. The subvol ioctl does: btrfsctl -S subvol_name parent_dir After the ioctl is done subvol_name lives inside parent_dir. The snapshot ioctl does: btrfsctl -s path_for_snapshot root_to_snapshot path_for_snapshot can be an absolute or relative path. btrfsctl breaks it up into directory and basename components. root_to_snapshot can be any file or directory in the FS. The snapshot is taken of the entire root where that file lives. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Seed device supportYan Zheng2008-11-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Seed device is a special btrfs with SEEDING super flag set and can only be mounted in read-only mode. Seed devices allow people to create new btrfs on top of it. The new FS contains the same contents as the seed device, but it can be mounted in read-write mode. This patch does the following: 1) split code in btrfs_alloc_chunk into two parts. The first part does makes the newly allocated chunk usable, but does not do any operation that modifies the chunk tree. The second part does the the chunk tree modifications. This division is for the bootstrap step of adding storage to the seed device. 2) Update device management code to handle seed device. The basic idea is: For an FS grown from seed devices, its seed devices are put into a list. Seed devices are opened on demand at mounting time. If any seed device is missing or has been changed, btrfs kernel module will refuse to mount the FS. 3) make btrfs_find_block_group not return NULL when all block groups are read-only. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: mount ro and remount supportYan Zheng2008-11-12
| | | | | | | | | | | This patch adds mount ro and remount support. The main changes in patch are: adding btrfs_remount and related helper function; splitting the transaction related code out of close_ctree into btrfs_commit_super; updating allocator to properly handle read only block group. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: Improve metadata read latenciesChris Mason2008-11-13
| | | | | | | | | | | | | This fixes latency problems on metadata reads by making sure they don't go through the async submit queue, and by tuning down the amount of readahead done during btree searches. Also, the btrfs bdi congestion function is tuned to ignore the number of pending async bios and checksums pending. There is additional code that throttles new async bios now and the congestion function doesn't need to worry about it anymore. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: tune btrfs unplug functions for a small number of devicesChris Mason2008-11-10
| | | | | | | | | | | | When btrfs unplugs, it tries to find the correct device to unplug via search through the extent_map tree. This avoids unplugging a device that doesn't need it, but is a waste of time for filesystems with a small number of devices. This patch checks the total number of devices before doing the search. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Optimize compressed writeback and readsChris Mason2008-11-06
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When reading compressed extents, try to put pages into the page cache for any pages covered by the compressed extent that readpages didn't already preload. Add an async work queue to handle transformations at delayed allocation processing time. Right now this is just compression. The workflow is: 1) Find offsets in the file marked for delayed allocation 2) Lock the pages 3) Lock the state bits 4) Call the async delalloc code The async delalloc code clears the state lock bits and delalloc bits. It is important this happens before the range goes into the work queue because otherwise it might deadlock with other work queue items that try to lock those extent bits. The file pages are compressed, and if the compression doesn't work the pages are written back directly. An ordered work queue is used to make sure the inodes are written in the same order that pdflush or writepages sent them down. This changes extent_write_cache_pages to let the writepage function update the wbc nr_written count. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Add ordered async work queuesChris Mason2008-11-06
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Btrfs uses kernel threads to create async work queues for cpu intensive operations such as checksumming and decompression. These work well, but they make it difficult to keep IO order intact. A single writepages call from pdflush or fsync will turn into a number of bios, and each bio is checksummed in parallel. Once the checksum is computed, the bio is sent down to the disk, and since we don't control the order in which the parallel operations happen, they might go down to the disk in almost any order. The code deals with this somewhat by having deep work queues for a single kernel thread, making it very likely that a single thread will process all the bios for a single inode. This patch introduces an explicitly ordered work queue. As work structs are placed into the queue they are put onto the tail of a list. They have three callbacks: ->func (cpu intensive processing here) ->ordered_func (order sensitive processing here) ->ordered_free (free the work struct, all processing is done) The work struct has three callbacks. The func callback does the cpu intensive work, and when it completes the work struct is marked as done. Every time a work struct completes, the list is checked to see if the head is marked as done. If so the ordered_func callback is used to do the order sensitive processing and the ordered_free callback is used to do any cleanup. Then we loop back and check the head of the list again. This patch also changes the checksumming code to use the ordered workqueues. One a 4 drive array, it increases streaming writes from 280MB/s to 350MB/s. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Add root tree pointer transaction idsYan Zheng2008-10-29
| | | | | | | | | | | This patch adds transaction IDs to root tree pointers. Transaction IDs in tree pointers are compared with the generation numbers in block headers when reading root blocks of trees. This can detect some types of IO errors. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: nuke fs wide allocation mutex V2Josef Bacik2008-10-29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch removes the giant fs_info->alloc_mutex and replaces it with a bunch of little locks. There is now a pinned_mutex, which is used when messing with the pinned_extents extent io tree, and the extent_ins_mutex which is used with the pending_del and extent_ins extent io trees. The locking for the extent tree stuff was inspired by a patch that Yan Zheng wrote to fix a race condition, I cleaned it up some and changed the locking around a little bit, but the idea remains the same. Basically instead of holding the extent_ins_mutex throughout the processing of an extent on the extent_ins or pending_del trees, we just hold it while we're searching and when we clear the bits on those trees, and lock the extent for the duration of the operations on the extent. Also to keep from getting hung up waiting to lock an extent, I've added a try_lock_extent so if we cannot lock the extent, move on to the next one in the tree and we'll come back to that one. I have tested this heavily and it does not appear to break anything. This has to be applied on top of my find_free_extent redo patch. I tested this patch on top of Yan's space reblancing code and it worked fine. The only thing that has changed since the last version is I pulled out all my debugging stuff, apparently I forgot to run guilt refresh before I sent the last patch out. Thank you, Signed-off-by: Josef Bacik <jbacik@redhat.com>
* Btrfs: Improve space balancing codeYan Zheng2008-10-29
| | | | | | | | | | | | | | | | | | | | | This patch improves the space balancing code to keep more sharing of tree blocks. The only case that breaks sharing of tree blocks is data extents get fragmented during balancing. The main changes in this patch are: Add a 'drop sub-tree' function. This solves the problem in old code that BTRFS_HEADER_FLAG_WRITTEN check breaks sharing of tree block. Remove relocation mapping tree. Relocation mappings are stored in struct btrfs_ref_path and updated dynamically during walking up/down the reference path. This reduces CPU usage and simplifies code. This patch also fixes a bug. Root items for reloc trees should be updated in btrfs_free_reloc_root. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
* Btrfs: Add zlib compression supportChris Mason2008-10-29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is a large change for adding compression on reading and writing, both for inline and regular extents. It does some fairly large surgery to the writeback paths. Compression is off by default and enabled by mount -o compress. Even when the -o compress mount option is not used, it is possible to read compressed extents off the disk. If compression for a given set of pages fails to make them smaller, the file is flagged to avoid future compression attempts later. * While finding delalloc extents, the pages are locked before being sent down to the delalloc handler. This allows the delalloc handler to do complex things such as cleaning the pages, marking them writeback and starting IO on their behalf. * Inline extents are inserted at delalloc time now. This allows us to compress the data before inserting the inline extent, and it allows us to insert an inline extent that spans multiple pages. * All of the in-memory extent representations (extent_map.c, ordered-data.c etc) are changed to record both an in-memory size and an on disk size, as well as a flag for compression. From a disk format point of view, the extent pointers in the file are changed to record the on disk size of a given extent and some encoding flags. Space in the disk format is allocated for compression encoding, as well as encryption and a generic 'other' field. Neither the encryption or the 'other' field are currently used. In order to limit the amount of data read for a single random read in the file, the size of a compressed extent is limited to 128k. This is a software only limit, the disk format supports u64 sized compressed extents. In order to limit the ram consumed while processing extents, the uncompressed size of a compressed extent is limited to 256k. This is a software only limit and will be subject to tuning later. Checksumming is still done on compressed extents, and it is done on the uncompressed version of the data. This way additional encodings can be layered on without having to figure out which encoding to checksum. Compression happens at delalloc time, which is basically singled threaded because it is usually done by a single pdflush thread. This makes it tricky to spread the compression load across all the cpus on the box. We'll have to look at parallel pdflush walks of dirty inodes at a later time. Decompression is hooked into readpages and it does spread across CPUs nicely. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: disk-io.c (open_ctree): avoid leaks upon allocation failureJim Meyering2008-10-01
| | | | Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: disk-io.c (open_ctree): Don't deref. NULL upon failed kzallocJim Meyering2008-10-01
| | | | | Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: add and improve commentsChris Mason2008-09-29
| | | | | | | | | | | This improves the comments at the top of many functions. It didn't dive into the guts of functions because I was trying to avoid merging problems with the new allocator and back reference work. extent-tree.c and volumes.c were both skipped, and there is definitely more work todo in cleaning and commenting the code. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Wait for IO on the block device inodes of newly added devicesChris Mason2008-09-29
| | | | | | | | | | | | | | | | | | | btrfs-vol -a /dev/xxx will zero the first and last two MB of the device. The kernel code needs to wait for this IO to finish before it adds the device. btrfs metadata IO does not happen through the block device inode. A separate address space is used, allowing the zero filled buffer heads in the block device inode to be written to disk after FS metadata starts going down to the disk via the btrfs metadata inode. The end result is zero filled metadata blocks after adding new devices into the filesystem. The fix is a simple filemap_write_and_wait on the block device inode before actually inserting it into the pool of available devices. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: update space balancing codeZheng Yan2008-09-26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch updates the space balancing code to utilize the new backref format. Before, btrfs-vol -b would break any COW links on data blocks or metadata. This was slow and caused the amount of space used to explode if a large number of snapshots were present. The new code can keeps the sharing of all data extents and most of the tree blocks. To maintain the sharing of data extents, the space balance code uses a seperate inode hold data extent pointers, then updates the references to point to the new location. To maintain the sharing of tree blocks, the space balance code uses reloc trees to relocate tree blocks in reference counted roots. There is one reloc tree for each subvol, and all reloc trees share same root key objectid. Reloc trees are snapshots of the latest committed roots of subvols (root->commit_root). To relocate a tree block referenced by a subvol, there are two steps. COW the block through subvol's reloc tree, then update block pointer in the subvol to point to the new block. Since all reloc trees share same root key objectid, doing special handing for tree blocks owned by them is easy. Once a tree block has been COWed in one reloc tree, we can use the resulting new block directly when the same block is required to COW again through other reloc trees. In this way, relocated tree blocks are shared between reloc trees, so they are also shared between subvols. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Add shared reference cacheZheng Yan2008-09-26
| | | | | | | | | | | | | Btrfs has a cache of reference counts in leaves, allowing it to avoid reading tree leaves while deleting snapshots. To reduce contention with multiple subvolumes, this cache is private to each subvolume. This patch adds shared reference cache support. The new space balancing code plays with multiple subvols at the same time, So the old per-subvol reference cache is not well suited. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Btrfs: Raise thresholds for metadata writebackChris Mason2008-09-25
| | | | | | | | | | | | | Btrfs metadata writeback is fairly expensive. Once a tree block is written it must be cowed before it can be changed again. The btree writepages code has a threshold based on a count of dirty btree bytes which is updated as IO is sent out. This changes btree_writepages to skip the writeout if there are less than 32MB of dirty bytes from the btrees, improving performance across many workloads. Signed-off-by: Chris Mason <chris.mason@oracle.com>
* Remove Btrfs compat code for older kernelsChris Mason2008-09-25
| | | | | | | | Btrfs had compatibility code for kernels back to 2.6.18. These have been removed, and will be maintained in a separate backport git tree from now on. Signed-off-by: Chris Mason <chris.mason@oracle.com>