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2011-11-06btrfs: separate superblock items out of fs_infoDavid Sterba
fs_info has now ~9kb, more than fits into one page. This will cause mount failure when memory is too fragmented. Top space consumers are super block structures super_copy and super_for_commit, ~2.8kb each. Allocate them dynamically. fs_info will be ~3.5kb. (measured on x86_64) Add a wrapper for freeing fs_info and all of it's dynamically allocated members. Signed-off-by: David Sterba <dsterba@suse.cz>
2011-09-11Btrfs: skip locking if searching the commit root in csum lookupJosef Bacik
It's not enough to just search the commit root, since we could be cow'ing the very block we need to search through, which would mean that its locked and we'll still deadlock. So use path->skip_locking as well. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-08-01Merge branch 'alloc_path' of ↵Chris Mason
git://git.kernel.org/pub/scm/linux/kernel/git/mfasheh/btrfs-error-handling into for-linus
2011-07-27Btrfs: use the commit_root for reading free_space_inode crcsChris Mason
Now that we are using regular file crcs for the free space cache, we can deadlock if we try to read the free_space_inode while we are updating the crc tree. This commit fixes things by using the commit_root to read the crcs. This is safe because we the free space cache file would already be loaded if that block group had been changed in the current transaction. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-07-27Btrfs: stop using highmem for extent_buffersChris Mason
The extent_buffers have a very complex interface where we use HIGHMEM for metadata and try to cache a kmap mapping to access the memory. The next commit adds reader/writer locks, and concurrent use of this kmap cache would make it even more complex. This commit drops the ability to use HIGHMEM with extent buffers, and rips out all of the related code. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-07-14btrfs: don't BUG_ON btrfs_alloc_path() errorsMark Fasheh
This patch fixes many callers of btrfs_alloc_path() which BUG_ON allocation failure. All the sites that are fixed in this patch were checked by me to be fairly trivial to fix because of at least one of two criteria: - Callers of the function catch errors from it already so bubbling the error up will be handled. - Callers of the function might BUG_ON any nonzero return code in which case there is no behavior changed (but we still got to remove a BUG_ON) The following functions were updated: btrfs_lookup_extent, alloc_reserved_tree_block, btrfs_remove_block_group, btrfs_lookup_csums_range, btrfs_csum_file_blocks, btrfs_mark_extent_written, btrfs_inode_by_name, btrfs_new_inode, btrfs_symlink, insert_reserved_file_extent, and run_delalloc_nocow Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2011-05-23Merge branch 'cleanups_and_fixes' into inode_numbersChris Mason
Conflicts: fs/btrfs/tree-log.c fs/btrfs/volumes.c Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-05-23Btrfs: BUG_ON is deleted from the caller of btrfs_truncate_item & ↵Tsutomu Itoh
btrfs_extend_item Currently, btrfs_truncate_item and btrfs_extend_item returns only 0. So, the check by BUG_ON in the caller is unnecessary. Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-05-23Btrfs: return error code to caller when btrfs_del_item failsTsutomu Itoh
The error code is returned instead of calling BUG_ON when btrfs_del_item returns the error. Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-05-23Merge branch 'for-chris' of ↵Chris Mason
git://git.kernel.org/pub/scm/linux/kernel/git/arne/btrfs-unstable-arne into inode_numbers Conflicts: fs/btrfs/Makefile fs/btrfs/ctree.h fs/btrfs/volumes.h Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-05-22Merge branch 'cleanups' of git://repo.or.cz/linux-2.6/btrfs-unstable into ↵Chris Mason
inode_numbers Conflicts: fs/btrfs/extent-tree.c fs/btrfs/free-space-cache.c fs/btrfs/inode.c fs/btrfs/tree-log.c Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-05-12btrfs: scrubArne Jansen
This adds an initial implementation for scrub. It works quite straightforward. The usermode issues an ioctl for each device in the fs. For each device, it enumerates the allocated device chunks. For each chunk, the contained extents are enumerated and the data checksums fetched. The extents are read sequentially and the checksums verified. If an error occurs (checksum or EIO), a good copy is searched for. If one is found, the bad copy will be rewritten. All enumerations happen from the commit roots. During a transaction commit, the scrubs get paused and afterwards continue from the new roots. This commit is based on the series originally posted to linux-btrfs with some improvements that resulted from comments from David Sterba, Ilya Dryomov and Jan Schmidt. Signed-off-by: Arne Jansen <sensille@gmx.net>
2011-05-02btrfs: drop unused parameter from btrfs_release_pathDavid Sterba
parameter tree root it's not used since commit 5f39d397dfbe140a14edecd4e73c34ce23c4f9ee ("Btrfs: Create extent_buffer interface for large blocksizes") Signed-off-by: David Sterba <dsterba@suse.cz>
2011-04-25Btrfs: Always use 64bit inode numberLi Zefan
There's a potential problem in 32bit system when we exhaust 32bit inode numbers and start to allocate big inode numbers, because btrfs uses inode->i_ino in many places. So here we always use BTRFS_I(inode)->location.objectid, which is an u64 variable. There are 2 exceptions that BTRFS_I(inode)->location.objectid != inode->i_ino: the btree inode (0 vs 1) and empty subvol dirs (256 vs 2), and inode->i_ino will be used in those cases. Another reason to make this change is I'm going to use a special inode to save free ino cache, and the inode number must be > (u64)-256. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2011-03-28Btrfs: check return value of btrfs_alloc_path()Tsutomu Itoh
Adding the check on the return value of btrfs_alloc_path() to several places. And, some of callers are modified by this change. Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-03-28Btrfs: cleanup some BUG_ON()Tsutomu Itoh
This patch changes some BUG_ON() to the error return. (but, most callers still use BUG_ON()) Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-01-28Btrfs: do error checking in btrfs_del_csumsJosef Bacik
Got a report of a box panicing because we got a NULL eb in read_extent_buffer. His fs was borked and btrfs_search_path returned EIO, but we don't check for errors so the box paniced. Yes I know this will just make something higher up the stack panic, but that's a problem for future Josef. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-01-28btrfs: fix several uncheck memory allocationsliubo
To make btrfs more stable, add several missing necessary memory allocation checks, and when no memory, return proper errno. We've checked that some of those -ENOMEM errors will be returned to userspace, and some will be catched by BUG_ON() in the upper callers, and none will be ignored silently. Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-05-25Btrfs: add basic DIO read/write supportJosef Bacik
This provides basic DIO support for reading and writing. It does not do the work to recover from mismatching checksums, that will come later. A few design changes have been made from Jim's code (sorry Jim!) 1) Use the generic direct-io code. Jim originally re-wrote all the generic DIO code in order to account for all of BTRFS's oddities, but thanks to that work it seems like the best bet is to just ignore compression and such and just opt to fallback on buffered IO. 2) Fallback on buffered IO for compressed or inline extents. Jim's code did it's own buffering to make dio with compressed extents work. Now we just fallback onto normal buffered IO. 3) Use ordered extents for the writes so that all of the lock_extent() lookup_ordered() type checks continue to work. 4) Do the lock_extent() lookup_ordered() loop in readpage so we don't race with DIO writes. I've tested this with fsx and everything works great. This patch depends on my dio and filemap.c patches to work. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-05-25Btrfs: Metadata ENOSPC handling for tree logYan, Zheng
Previous patches make the allocater return -ENOSPC if there is no unreserved free metadata space. This patch updates tree log code and various other places to propagate/handle the ENOSPC error. Signed-off-by: Yan Zheng <zheng.yan@oracle.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-03-30include cleanup: Update gfp.h and slab.h includes to prepare for breaking ↵Tejun Heo
implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2009-03-24Btrfs: leave btree locks spinning more oftenChris Mason
btrfs_mark_buffer dirty would set dirty bits in the extent_io tree for the buffers it was dirtying. This may require a kmalloc and it was not atomic. So, anyone who called btrfs_mark_buffer_dirty had to set any btree locks they were holding to blocking first. This commit changes dirty tracking for extent buffers to just use a flag in the extent buffer. Now that we have one and only one extent buffer per page, this can be safely done without losing dirty bits along the way. This also introduces a path->leave_spinning flag that callers of btrfs_search_slot can use to indicate they will properly deal with a path returned where all the locks are spinning instead of blocking. Many of the btree search callers now expect spinning paths, resulting in better btree concurrency overall. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2009-01-06Btrfs: tree logging checksum fixesYan Zheng
This patch contains following things. 1) Limit the max size of btrfs_ordered_sum structure to PAGE_SIZE. This struct is kmalloced so we want to keep it reasonable. 2) Replace copy_extent_csums by btrfs_lookup_csums_range. This was duplicated code in tree-log.c 3) Remove replay_one_csum. csum items are replayed at the same time as replaying file extents. This guarantees we only replay useful csums. 4) nbytes accounting fix. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
2009-01-05Btrfs: Fix checkpatch.pl warningsChris Mason
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>
2008-12-17Btrfs: properly check free space for tree balancingYan Zheng
btrfs_insert_empty_items takes the space needed by the btrfs_item structure into account when calculating the required free space. So the tree balancing code shouldn't add sizeof(struct btrfs_item) to the size when checking the free space. This patch removes these superfluous additions. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
2008-12-16Btrfs: delete checksum items before marking blocks freeChris Mason
Btrfs maintains a cache of blocks available for allocation in ram. The code that frees extents was marking the extents free and then deleting the checksum items. This meant it was possible the extent would be reallocated before the checksum item was actually deleted, leading to races and other problems as the checksums were updated for the newly allocated extent. The fix is to delete the checksum before marking the extent free. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-12-12Btrfs: fix nodatasum handling in balancing codeYan Zheng
Checksums on data can be disabled by mount option, so it's possible some data extents don't have checksums or have invalid checksums. This causes trouble for data relocation. This patch contains following things to make data relocation work. 1) make nodatasum/nodatacow mount option only affects new files. Checksums and COW on data are only controlled by the inode flags. 2) check the existence of checksum in the nodatacow checker. If checksums exist, force COW the data extent. This ensure that checksum for a given block is either valid or does not exist. 3) update data relocation code to properly handle the case of checksum missing. Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
2008-12-10Btrfs: Delete csum items when freeing extentsChris Mason
This finishes off the new checksumming code by removing csum items for extents that are no longer in use. The trick is doing it without racing because a single csum item may hold csums for more than one extent. Extra checks are added to btrfs_csum_file_blocks to make sure that we are using the correct csum item after dropping locks. A new btrfs_split_item is added to split a single csum item so it can be split without dropping the leaf lock. This is used to remove csum bytes from the middle of an item. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-12-08Btrfs: move data checksumming into a dedicated treeChris Mason
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>
2008-12-02Btrfs: add support for multiple csum algorithmsJosef Bacik
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>
2008-11-10Btrfs: Use invalidatepage when writepage finds a page outside of i_sizeChris Mason
With all the recent fixes to the delalloc locking, it is now safe again to use invalidatepage inside the writepage code for pages outside of i_size. This used to deadlock against some of the code to write locked ranges of pages, but all of that has been fixed. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-10-29Btrfs: Add zlib compression supportChris Mason
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>
2008-09-25Btrfs: Fix variable init during csum creationChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Lookup readpage checksums on bio submission againChris Mason
This optimization had been removed because I thought it was triggering csum errors. The real cause of the errors was elsewhere, and so this optimization is back. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Lower contention on the csum mutexChris Mason
This takes the csum mutex deeper in the call chain and releases it more often. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25btrfs_lookup_bio_sums seems broken, go back to the readpage_io_hook for nowChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Hold csum mutex while reading in sums during readpagesChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Fix streaming read performance with checksumming onChris Mason
Large streaming reads make for large bios, which means each entry on the list async work queues represents a large amount of data. IO congestion throttling on the device was kicking in before the async worker threads decided a single thread was busy and needed some help. The end result was that a streaming read would result in a single CPU running at 100% instead of balancing the work off to other CPUs. This patch also changes the pre-IO checksum lookup done by reads to work on a per-bio basis instead of a per-page. This results in many extra btree lookups on large streaming reads. Doing the checksum lookup right before bio submit allows us to reuse searches while processing adjacent offsets. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: implement memory reclaim for leaf reference cacheYan
The memory reclaiming issue happens when snapshot exists. In that case, some cache entries may not be used during old snapshot dropping, so they will remain in the cache until umount. The patch adds a field to struct btrfs_leaf_ref to record create time. Besides, the patch makes all dead roots of a given snapshot linked together in order of create time. After a old snapshot was completely dropped, we check the dead root list and remove all cache entries created before the oldest dead root in the list. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Take the csum mutex while reading checksumsChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Fix btrfs_wait_ordered_extent_range to properly waitChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Keep extent mappings in ram until pending ordered extents are doneChris Mason
It was possible for stale mappings from disk to be used instead of the new pending ordered extent. This adds a flag to the extent map struct to keep it pinned until the pending ordered extent is actually on disk. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Handle data checksumming on bios that span multiple ordered extentsChris Mason
Data checksumming is done right before the bio is sent down the IO stack, which means a single bio might span more than one ordered extent. In this case, the checksumming data is split between two ordered extents. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: New data=ordered implementationChris Mason
The old data=ordered code would force commit to wait until all the data extents from the transaction were fully on disk. This introduced large latencies into the commit and stalled new writers in the transaction for a long time. The new code changes the way data allocations and extents work: * When delayed allocation is filled, data extents are reserved, and the extent bit EXTENT_ORDERED is set on the entire range of the extent. A struct btrfs_ordered_extent is allocated an inserted into a per-inode rbtree to track the pending extents. * As each page is written EXTENT_ORDERED is cleared on the bytes corresponding to that page. * When all of the bytes corresponding to a single struct btrfs_ordered_extent are written, The previously reserved extent is inserted into the FS btree and into the extent allocation trees. The checksums for the file data are also updated. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Clone file data ioctlSage Weil
Add a new ioctl to clone file data Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Write bio checksumming outside the FS mutexChris Mason
This significantly improves streaming write performance by allowing concurrency in the data checksumming. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Use KM_USERN instead of KM_IRQ during data summingChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: Make sure bio pages are adjacent during bulk csummingChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: While doing checksums on bios, cache the extent_buffer mappingChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25Btrfs: checksum file data at bio submission time instead of during writepageChris Mason
When we checkum file data during writepage, the checksumming is done one page at a time, making it difficult to do bulk metadata modifications to insert checksums for large ranges of the file at once. This patch changes btrfs to checksum on a per-bio basis instead. The bios are checksummed before they are handed off to the block layer, so each bio is contiguous and only has pages from the same inode. Checksumming on a bio basis allows us to insert and modify the file checksum items in large groups. It also allows the checksumming to be done more easily by async worker threads. Signed-off-by: Chris Mason <chris.mason@oracle.com>