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Merge tag 'xfs-perag-conv-tag' of...
Merge tag 'xfs-perag-conv-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs into xfs-5.14-merge2 xfs: initial agnumber -> perag conversions for shrink If we want to use active references to the perag to be able to gate shrink removing AGs and hence perags safely, we've got a fair bit of work to do actually use perags in all the places we need to. There's a lot of code that iterates ag numbers and then looks up perags from that, often multiple times for the same perag in the one operation. If we want to use reference counted perags for access control, then we need to convert all these uses to perag iterators, not agno iterators. [Patches 1-4] The first step of this is consolidating all the perag management - init, free, get, put, etc into a common location. THis is spread all over the place right now, so move it all into libxfs/xfs_ag.[ch]. This does expose kernel only bits of the perag to libxfs and hence userspace, so the structures and code is rearranged to minimise the number of ifdefs that need to be added to the userspace codebase. The perag iterator in xfs_icache.c is promoted to a first class API and expanded to the needs of the code as required. [Patches 5-10] These are the first basic perag iterator conversions and changes to pass the perag down the stack from those iterators where appropriate. A lot of this is obvious, simple changes, though in some places we stop passing the perag down the stack because the code enters into an as yet unconverted subsystem that still uses raw AGs. [Patches 11-16] These replace the agno passed in the btree cursor for per-ag btree operations with a perag that is passed to the cursor init function. The cursor takes it's own reference to the perag, and the reference is dropped when the cursor is deleted. Hence we get reference coverage for the entire time the cursor is active, even if the code that initialised the cursor drops it's reference before the cursor or any of it's children (duplicates) have been deleted. The first patch adds the perag infrastructure for the cursor, the next four patches convert a btree cursor at a time, and the last removes the agno from the cursor once it is unused. [Patches 17-21] These patches are a demonstration of the simplifications and cleanups that come from plumbing the perag through interfaces that select and then operate on a specific AG. In this case the inode allocation algorithm does up to three walks across all AGs before it either allocates an inode or fails. Two of these walks are purely just to select the AG, and even then it doesn't guarantee inode allocation success so there's a third walk if the selected AG allocation fails. These patches collapse the selection and allocation into a single loop, simplifies the error handling because xfs_dir_ialloc() always returns ENOSPC if no AG was selected for inode allocation or we fail to allocate an inode in any AG, gets rid of xfs_dir_ialloc() wrapper, converts inode allocation to run entirely from a single perag instance, and then factors xfs_dialloc() into a much, much simpler loop which is easy to understand. Hence we end up with the same inode allocation logic, but it only needs two complete iterations at worst, makes AG selection and allocation atomic w.r.t. shrink and chops out out over 100 lines of code from this hot code path. [Patch 22] Converts the unlink path to pass perags through it. There's more conversion work to be done, but this patchset gets through a large chunk of it in one hit. Most of the iterators are converted, so once this is solidified we can move on to converting these to active references for being able to free perags while the fs is still active. * tag 'xfs-perag-conv-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs: (23 commits) xfs: remove xfs_perag_t xfs: use perag through unlink processing xfs: clean up and simplify xfs_dialloc() xfs: inode allocation can use a single perag instance xfs: get rid of xfs_dir_ialloc() xfs: collapse AG selection for inode allocation xfs: simplify xfs_dialloc_select_ag() return values xfs: remove agno from btree cursor xfs: use perag for ialloc btree cursors xfs: convert allocbt cursors to use perags xfs: convert refcount btree cursor to use perags xfs: convert rmap btree cursor to using a perag xfs: add a perag to the btree cursor xfs: pass perags around in fsmap data dev functions xfs: push perags through the ag reservation callouts xfs: pass perags through to the busy extent code xfs: convert secondary superblock walk to use perags xfs: convert xfs_iwalk to use perag references xfs: convert raw ag walks to use for_each_perag xfs: make for_each_perag... a first class citizen ...