- 05 Oct, 2016 26 commits
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Darrick J. Wong authored
Prior to the introduction of reflink, allocating a block and mapping it into a file was performed in a single transaction with a single block reservation, and the allocator was supposed to find enough blocks to allocate the extent and any BMBT blocks that might be necessary (unless we're low on space). However, due to the way copy on write works, allocation and mapping have been split into two transactions, which means that we must be able to handle the case where we allocate an extent for CoW but that AG runs out of free space before the blocks can be mapped into a file, and the mapping requires a new BMBT block. When this happens, look in one of the other AGs for a BMBT block instead of taking the FS down. The same applies to the functions that convert a data fork to extents and later btree format. Signed-off-by:
Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by:
Christoph Hellwig <hch@lst.de>
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Darrick J. Wong authored
If the AG free space is down to the reserves, refuse to reflink our way out of space. Hopefully userspace will make a real copy and/or go elsewhere. Signed-off-by:
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Darrick J. Wong authored
To gracefully handle the situation where a CoW operation turns a single refcount extent into a lot of tiny ones and then run out of space when a tree split has to happen, use the per-AG reserved block pool to pre-allocate all the space we'll ever need for a maximal btree. For a 4K block size, this only costs an overhead of 0.3% of available disk space. When reflink is enabled, we have an unfortunate problem with rmap -- since we can share a block billions of times, this means that the reverse mapping btree can expand basically infinitely. When an AG is so full that there are no free blocks with which to expand the rmapbt, the filesystem will shut down hard. This is rather annoying to the user, so use the AG reservation code to reserve a "reasonable" amount of space for rmap. We'll prevent reflinks and CoW operations if we think we're getting close to exhausting an AG's free space rather than shutting down, but this permanent reservation should be enough for "most" users. Hopefully. Signed-off-by:
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Darrick J. Wong authored
Create a per-inode extent size allocator hint for copy-on-write. This hint is separate from the existing extent size hint so that CoW can take advantage of the fragmentation-reducing properties of extent size hints without disabling delalloc for regular writes. The extent size hint that's fed to the allocator during a copy on write operation is the greater of the cowextsize and regular extsize hint. During reflink, if we're sharing the entire source file to the entire destination file and the destination file doesn't already have a cowextsize hint, propagate the source file's cowextsize hint to the destination file. Furthermore, zero the bulkstat buffer prior to setting the fields so that we don't copy kernel memory contents into userspace. Signed-off-by:
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Darrick J. Wong authored
Unshare all shared extents if the user calls fallocate with the new unshare mode flag set, so that we can guarantee that a subsequent write will not ENOSPC. Signed-off-by:
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Darrick J. Wong authored
When we're swapping the extents of two inodes, be sure to swap the reflink inode flag too. Signed-off-by:
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Darrick J. Wong authored
Teach xfs_getbmapx how to report shared extents and CoW fork contents accurately in the bmap output by querying the refcount btree appropriately. Signed-off-by:
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Darrick J. Wong authored
Define a VFS function which allows userspace to request that the kernel reflink a range of blocks between two files if the ranges' contents match. The function fits the new VFS ioctl that standardizes the checking for the btrfs EXTENT SAME ioctl. Signed-off-by:
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Darrick J. Wong authored
Define two VFS functions which allow userspace to reflink a range of blocks between two files or to reflink one file's contents to another. These functions fit the new VFS ioctls that standardize the checking for the btrfs CLONE and CLONE RANGE ioctls. Signed-off-by:
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Darrick J. Wong authored
Reflink extents from one file to another; that is to say, iteratively remove the mappings from the destination file, copy the mappings from the source file to the destination file, and increment the reference count of all the blocks that got remapped. Signed-off-by:
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Darrick J. Wong authored
Due to the way the CoW algorithm in XFS works, there's an interval during which blocks allocated to handle a CoW can be lost -- if the FS goes down after the blocks are allocated but before the block remapping takes place. This is exacerbated by the cowextsz hint -- allocated reservations can sit around for a while, waiting to get used. Since the refcount btree doesn't normally store records with refcount of 1, we can use it to record these in-progress extents. In-progress blocks cannot be shared because they're not user-visible, so there shouldn't be any conflicts with other programs. This is a better solution than holding EFIs during writeback because (a) EFIs can't be relogged currently, (b) even if they could, EFIs are bound by available log space, which puts an unnecessary upper bound on how much CoW we can have in flight, and (c) we already have a mechanism to track blocks. At mount time, read the refcount records and free anything we find with a refcount of 1 because those were in-progress when the FS went down. Signed-off-by:
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Darrick J. Wong authored
When destroying the inode, cancel all pending reservations in the CoW fork so that all the reserved blocks go back to the free pile. In theory this sort of cleanup is only needed to clean up after write errors. Signed-off-by:
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Darrick J. Wong authored
When we're freeing blocks (truncate, punch, etc.), clear all CoW reservations in the range being freed. If the file block count drops to zero, also clear the inode reflink flag. Signed-off-by:
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Darrick J. Wong authored
For O_DIRECT writes to shared blocks, we have to CoW them just like we would with buffered writes. For writes that are not block-aligned, just bounce them to the page cache. For block-aligned writes, however, we can do better than that. Use the same mechanisms that we employ for buffered CoW to set up a delalloc reservation, allocate all the blocks at once, issue the writes against the new blocks and use the same ioend functions to remap the blocks after the write. This should be fairly performant. Christoph discovered that xfs_reflink_allocate_cow_range may stumble over invalid entries in the extent array given that it drops the ilock but still expects the index to be stable. Simple fixing it to a new lookup for every iteration still isn't correct given that xfs_bmapi_allocate will trigger a BUG_ON() if hitting a hole, and there is nothing preventing a xfs_bunmapi_cow call removing extents once we dropped the ilock either. This patch duplicates the inner loop of xfs_bmapi_allocate into a helper for xfs_reflink_allocate_cow_range so that it can be done under the same ilock critical section as our CoW fork delayed allocation. The directio CoW warts will be revisited in a later patch. Signed-off-by:
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Darrick J. Wong authored
Report shared extents through the iomap interface so that FIEMAP flags shared blocks accurately. Have xfs_vm_bmap return zero for reflinked files because the bmap-based swap code requires static block mappings, which is incompatible with copy on write. NOTE: Existing userspace bmap users such as lilo will have the same problem with reflink files. Signed-off-by:
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Darrick J. Wong authored
After the write component of a copy-write operation finishes, clean up the bookkeeping left behind. On error, we simply free the new blocks and pass the error up. If we succeed, however, then we must remove the old data fork mapping and move the cow fork mapping to the data fork. Signed-off-by:
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Darrick J. Wong authored
Create a helper method to remove extents from the CoW fork without any of the side effects (rmapbt/bmbt updates) of the regular extent deletion routine. We'll eventually use this to clear out the CoW fork during ioend processing. Signed-off-by:
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Darrick J. Wong authored
Modify the writepage handler to find and convert pending delalloc extents to real allocations. Furthermore, when we're doing non-cow writes to a part of a file that already has a CoW reservation (the cowextsz hint that we set up in a subsequent patch facilitates this), promote the write to copy-on-write so that the entire extent can get written out as a single extent on disk, thereby reducing post-CoW fragmentation. Christoph moved the CoW support code in _map_blocks to a separate helper function, refactored other functions, and reduced the number of CoW fork lookups, so I merged those changes here to reduce churn. Signed-off-by:
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Darrick J. Wong authored
Modify xfs_bmap_add_extent_delay_real() so that we can convert delayed allocation extents in the CoW fork to real allocations, and wire this up all the way back to xfs_iomap_write_allocate(). In a subsequent patch, we'll modify the writepage handler to call this. Signed-off-by:
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Darrick J. Wong authored
Wire up iomap_begin to detect shared extents and create delayed allocation extents in the CoW fork: 1) Check if we already have an extent in the COW fork for the area. If so nothing to do, we can move along. 2) Look up block number for the current extent, and if there is none it's not shared move along. 3) Unshare the current extent as far as we are going to write into it. For this we avoid an additional COW fork lookup and use the information we set aside in step 1) above. 4) Goto 1) unless we've covered the whole range. Last but not least, this updates the xfs_reflink_reserve_cow_range calling convention to pass a byte offset and length, as that is what both callers expect anyway. This patch has been refactored considerably as part of the iomap transition. Signed-off-by: -
Darrick J. Wong authored
Allow the creation of delayed allocation extents in the CoW fork. In a subsequent patch we'll wire up iomap_begin to actually do this via reflink helper functions. Signed-off-by:
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Darrick J. Wong authored
Introduce a new in-core fork for storing copy-on-write delalloc reservations and allocated extents that are in the process of being written out. Signed-off-by:
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Darrick J. Wong authored
Only non-rt files can be reflinked, so check that when we load an inode. Also, don't leak the attr fork if there's a failure. Signed-off-by:
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Darrick J. Wong authored
Report the reflink feature in the XFS geometry so that xfs_info and friends know the filesystem has this feature. Signed-off-by:
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Darrick J. Wong authored
Define all the tracepoints we need to inspect the runtime operation of reflink/dedupe/copy-on-write. Signed-off-by:
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Darrick J. Wong authored
Return the range of file blocks that bunmapi didn't free. This hint is used by CoW and reflink to figure out what part of an extent actually got freed so that it can set up the appropriate atomic remapping of just the freed range. Signed-off-by:
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- 04 Oct, 2016 6 commits
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Darrick J. Wong authored
Log recovery will iget an inode to replay BUI items and iput the inode when it's done. Unfortunately, if the inode was unlinked, the iput will see that i_nlink == 0 and decide to truncate & free the inode, which prevents us from replaying subsequent BUIs. We can't skip the BUIs because we have to replay all the redo items to ensure that atomic operations complete. Since unlinked inode recovery will reap the inode anyway, we can safely introduce a new inode flag to indicate that an inode is in this 'unlinked recovery' state and should not be auto-reaped in the drop_inode path. Signed-off-by:
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Darrick J. Wong authored
Implement deferred versions of the inode block map/unmap functions. These will be used in subsequent patches to make reflink operations atomic. Signed-off-by:
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Darrick J. Wong authored
Pass BMAPI_ flags from bunmapi into bmap_del_extent and extend BMAPI_REMAP (which means "don't touch the allocator or the quota accounting") to apply to bunmapi as well. This will be used to implement the unmap operation, which will be used by swapext. Signed-off-by:
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Darrick J. Wong authored
Teach the bmap routine to know how to map a range of file blocks to a specific range of physical blocks, instead of simply allocating fresh blocks. This enables reflink to map a file to blocks that are already in use. Signed-off-by:
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Darrick J. Wong authored
Provide a mechanism for higher levels to create BUI/BUD items, submit them to the log, and a stub function to deal with recovered BUI items. These parts will be connected to the rmapbt in a later patch. Signed-off-by:
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Darrick J. Wong authored
Create bmbt update intent/done log items to record redo information in the log. Because we roll transactions multiple times for reflink operations, we also have to track the status of the metadata updates that will be recorded in the post-roll transactions in case we crash before committing the final transaction. This mechanism enables log recovery to finish what was already started. Signed-off-by:
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- 03 Oct, 2016 8 commits
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Darrick J. Wong authored
These functions will be used by the other reflink functions to find the maximum length of a range of shared blocks. Signed-off-by:
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Darrick J. Wong authored
Reduce the max AG usable space size so that we always have space for the refcount btree root. Signed-off-by:
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Darrick J. Wong authored
Identify refcountbt blocks in the log correctly so that we can validate them during log recovery. Signed-off-by:
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Darrick J. Wong authored
When we're unmapping blocks from a reflinked file, decrease the refcount of the affected blocks and free the extents that are no longer in use. Signed-off-by:
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Darrick J. Wong authored
Plumb in the upper level interface to schedule and finish deferred refcount operations via the deferred ops mechanism. Signed-off-by:
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Darrick J. Wong authored
Provide functions to adjust the reference counts for an extent of physical blocks stored in the refcount btree. Signed-off-by:
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Darrick J. Wong authored
Provide a mechanism for higher levels to create CUI/CUD items, submit them to the log, and a stub function to deal with recovered CUI items. These parts will be connected to the refcountbt in a later patch. Signed-off-by:
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Darrick J. Wong authored
Create refcount update intent/done log items to record redo information in the log. Because we need to roll transactions between updating the bmbt mapping and updating the reverse mapping, we also have to track the status of the metadata updates that will be recorded in the post-roll transactions, just in case we crash before committing the final transaction. This mechanism enables log recovery to finish what was already started. Signed-off-by:
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