- 10 Oct, 2016 3 commits
-
-
Darrick J. Wong authored
Now that fallocate has an explicit unshare flag again, let's try to remove the inode reflink flag whenever the user unshares any part of a file since checking is cheap compared to the CoW. Signed-off-by:
Darrick J. Wong <darrick.wong@oracle.com> Reported-by:
Brian Foster <bfoster@redhat.com> Reviewed-by:
Dave Chinner <dchinner@redhat.com> Signed-off-by:
Dave Chinner <david@fromorbit.com>
-
Darrick J. Wong authored
The loop in _reflink_clear_inode_flag isn't necessary since we jump out if any part of any extent is shared. Remove the loop and we no longer need two maps, so we can save some stack use. Signed-off-by:
-
Darrick J. Wong authored
There are a couple of places where we don't check the inode's reflink flag before calling into the reflink code. Fix those, and add some asserts so we don't make this mistake again. Signed-off-by:
-
- 05 Oct, 2016 37 commits
-
-
Darrick J. Wong authored
Implement swapext for filesystems that have reverse mapping. Back in the reflink patches, we augmented the bmap code with a 'REMAP' flag that updates only the bmbt and doesn't touch the allocator and implemented log redo items for those two operations. Now we can rewrite extent swapping as a (looong) series of remap operations. This is far less efficient than the fork swapping method implemented in the past, so we only switch this on for rmap. Signed-off-by:
Christoph Hellwig <hch@lst.de>
-
Darrick J. Wong authored
Refactor the swapext function to pull out the fork swapping piece into a separate function. In the next patch we'll add in the bit we need to make it work with rmap filesystems. Signed-off-by:
-
Darrick J. Wong authored
Replace structure typedefs with struct expressions and fix some whitespace issues that result. Signed-off-by:
-
Darrick J. Wong authored
Add the reflink feature flag to the set of recognized feature flags. This enables users to write to reflink filesystems. Signed-off-by:
-
Darrick J. Wong authored
Create an error injection point that enables us to simulate being critically low on per-AG block reservations. This should enable us to simulate this specific ENOSPC condition so that we can test falling back to a regular file copy. Signed-off-by:
-
Darrick J. Wong authored
Since we don't have a strategy for handling both DAX and reflink, for now we'll just prohibit both being set at the same time. Signed-off-by:
-
Darrick J. Wong authored
We don't support sharing blocks on the realtime device. Flag inodes with the reflink or cowextsize flags set when the reflink feature is disabled. Signed-off-by:
-
Darrick J. Wong authored
If the admin doesn't set a CoW extent size or a regular extent size hint, default to creating CoW reservations 32 blocks long to reduce fragmentation. Signed-off-by:
-
Darrick J. Wong authored
Provide a function to convert an unwritten extent to a real one and vice versa when shared extents are possible. Signed-off-by:
-
Darrick J. Wong authored
When it's possible for reverse mappings to overlap (data fork extents of files on reflink filesystems), use the interval query function to find the left neighbor of an extent we're trying to add; and be careful to use the lookup functions to update the neighbors and/or add new extents. Signed-off-by:
-
Darrick J. Wong authored
Wire up some rmap log redo item type codes to map, unmap, or convert shared data block extents. The actual log item recovery comes in a later patch. Signed-off-by:
-
Darrick J. Wong authored
Increase the log reservations to handle the increased rolling that happens at the end of copy-on-write operations. Signed-off-by:
-
Darrick J. Wong authored
Trim CoW reservations made on behalf of a cowextsz hint if they get too old or we run low on quota, so long as we don't have dirty data awaiting writeback or directio operations in progress. Garbage collection of the cowextsize extents are kept separate from prealloc extent reaping because setting the CoW prealloc lifetime to a (much) higher value than the regular prealloc extent lifetime has been useful for combatting CoW fragmentation on VM hosts where the VMs experience bursty write behaviors and we can keep the utilization ratios low enough that we don't start to run out of space. IOWs, it benefits us to keep the CoW fork reservations around for as long as we can unless we run out of blocks or hit inode reclaim. Signed-off-by:
-
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 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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
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:
-
