bcachefs: document btree iter flags #287
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…dvance The way btree iterators work internally has been changing, particularly with the iter->real_pos changes, and bch2_btree_iter_next() is no longer hyper optimized - it's just advance followed by peek, so it's more efficient to just call advance where we're not using the return value of bch2_btree_iter_next(). Signed-off-by: Kent Overstreet <[email protected]>
btree node iterators need to obey the regular btree node invarionts w.r.t. iter->real_pos; once they do, bch2_btree_iter_traverse will have less that it needs to check. Signed-off-by: Kent Overstreet <[email protected]>
This means bch2_btree_iter_traverse_one() can be made more efficient. Signed-off-by: Kent Overstreet <[email protected]>
Since we're no longer doing next() immediately followed by peek(), this optimization isn't doing anything anymore. Signed-off-by: Kent Overstreet <[email protected]>
This just gives some internal helpers some better names. Signed-off-by: Kent Overstreet <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
Ideally we'll be getting rid of peek_with_updates(), but the callers will need to be checked. Signed-off-by: Kent Overstreet <[email protected]>
peek() has to update iter->real_pos - there's no need for bch2_btree_iter_set_pos() to update it as well. Signed-off-by: Kent Overstreet <[email protected]>
More prep work for snapshots. Signed-off-by: Kent Overstreet <[email protected]>
It was using the method for btree_ptr_v1, but that wasn't checking all the fields. Signed-off-by: Kent Overstreet <[email protected]>
It had some silly redundancies. Signed-off-by: Kent Overstreet <[email protected]>
External (to the btree iterator code) users of bch2_btree_iter_traverse expect that on success the iterator will be pointed at iter->pos and have that position locked - but since we split iter->pos and iter->real_pos, that means it has to update iter->real_pos if necessary. Internal users don't expect it to modify iter->real_pos, so we need two separate functions. Signed-off-by: Kent Overstreet <[email protected]>
This adds a mode to six locks where readers use percpu counters - avoiding writing to shared cachelines. The algorithm is the same as the existing percpu-rwsemaphore's slowpath algorithm: taking a read lock still requires a memory barrier to check if we raced with another thread taking a write lock, but this means that taking a write lock doesn't incur the cost of an RCU barrier. Signed-off-by: Kent Overstreet <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
The default was 1/256th of the device and capped at 512MB, which is fairly tiny these days. Signed-off-by: Kent Overstreet <[email protected]>
Bkey noops were introduced to deal with trimming inline data extents in place in the btree: if the u64s field of a bkey was 0, that u64 was a noop and we'd start looking for the next bkey immediately after it. But extent handling has been lifted above the btree - we no longer modify existing extents in place in the btree, and the compatibilty code for old style extent btree nodes is gone, so we can completely drop this code. Signed-off-by: Kent Overstreet <[email protected]>
On btree node split, we weren't ensuring the min_key of the new larger node packs in the new format for this node. This triggers some painful slowpaths in the bset.c aux search tree code - this patch fixes that by calculating a new format for the new node with the new min_key. Signed-off-by: Kent Overstreet <[email protected]>
We weren't packing the min/max keys, which was a major oversight and completely disabled generating bkey_floats for adjacent nodes. Signed-off-by: Kent Overstreet <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
…d to When we pass BTREE_INSERT_NOUNLOCK bch2_trans_commit isn't supposed to unlock after a successful commit, but it was calling bch2_trans_cond_resched() - oops. Signed-off-by: Kent Overstreet <[email protected]>
Since we now make sure to always generate packed bkey formats that can pack the min_key of a btree node, this path should actually never happen. Signed-off-by: Kent Overstreet <[email protected]>
The btree key cache mutex was becoming a significant bottleneck - it was mainly used to protect the lists of dirty, clean and freed cached keys. This patch eliminates the dirty and clean lists - instead, when we need to scan for keys to drop from the cache we iterate over the rhashtable, and thus we're able to remove most uses of that lock. Signed-off-by: Kent Overstreet <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
With snapshots, we're going to need to differentiate between comparisons that should and shouldn't include the snapshot field. bpos_cmp is now the comparison function that does include the snapshot field, used by core btree code. Upper level filesystem code generally does _not_ want to compare against the snapshot field - that code wants keys to compare as equal even when one of them is in an ancestor snapshot. Signed-off-by: Kent Overstreet <[email protected]>
This patch starts treating the bpos.snapshot field like part of the key in the btree code: * bpos_successor() and bpos_predecessor() now include the snapshot field * Keys in btrees that will be using snapshots (extents, inodes, dirents and xattrs) now always have their snapshot field set to U32_MAX The btree iterator code gets a new flag, BTREE_ITER_ALL_SNAPSHOTS, that determines whether we're iterating over keys in all snapshots or not - internally, this controlls whether bkey_(successor|predecessor) increment/decrement the snapshot field, or only the higher bits of the key. We add a new member to struct btree_iter, iter->snapshot: when BTREE_ITER_ALL_SNAPSHOTS is not set, iter->pos.snapshot should always equal iter->snapshot, which will be 0 for btrees that don't use snapshots, and alsways U32_MAX for btrees that will use snapshots (until we enable snapshot creation). This patch also introduces a new metadata version number, and compat code for reading from/writing to older versions - this isn't a forced upgrade (yet). Signed-off-by: Kent Overstreet <[email protected]>
This patch adds two new inode fields, bi_dir and bi_dir_offset, that point back to the inode's dirent. Since we're only adding fields for a single backpointer, files that have been hardlinked won't necessarily have valid backpointers: we also add a new inode flag, BCH_INODE_BACKPTR_UNTRUSTED, that's set if an inode has ever had multiple links to it. That's ok, because we only really need this functionality for directories, which can never have multiple hardlinks - when we add subvolumes, we'll need a way to enemurate and print subvolumes, and this will let us reconstruct a path to a subvolume root given a subvolume root inode. Signed-off-by: Kent Overstreet <[email protected]>
For snapshots, when we allocate a new inode we want to allocate an inode number that isn't in use in any other subvolume. We won't be able to use ITER_SLOTS for this, inode allocation needs to change to use BTREE_ITER_ALL_SNAPSHOTS. Signed-off-by: Kent Overstreet <[email protected]>
Since move.c isn't aware of what subvolume we're in, we can't use the standard inode lookup code - fortunately, we're just using it for reading IO options. Signed-off-by: Kent Overstreet <[email protected]>
This adds a new watermark for the journal reclaim when flushing btree key cache entries - it should try and stay ahead of where foreground threads doing transaction commits will enter direct journal reclaim. Signed-off-by: Kent Overstreet <[email protected]>
This is specifically to speed up bch2_inode_rm(), so that we're not traversing iterators we're done with. Signed-off-by: Kent Overstreet <[email protected]>
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Add documentation commets to the btree iter flag definitions.
CC: #269
Signed-off-by: Dan Robertson [email protected]