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Linus Torvalds
96a377ba00
Pull path lookup updates from Christian Brauner: "This prepares for Neil's changes to directory locking. The goal is for the VFS to lock the dentry and not the parent directory and to push the i_rwsem parent locking down into the filesystems where it can be kept, removed or adjusted as each filesystem sees fit. The next step in that is to swap the lock order of d_alloc_parallel() and i_rwsem so code can wait on i_rwsem while holding an in-lookup dentry. Two things have to change before that can happen. Nobody may call d_alloc_parallel() while holding i_rwsem, and nobody may d_drop() a dentry while it is being worked on since that effectively unlocks an in-lookup dentry and lets another one be allocated too early. So d_splice_alias() learns to handle hashed dentries in addition to unhashed and in-lookup ones, which is what ->atomic_open() needs and removes the reason filesystems d_drop() first. d_alloc_trylock() is a non-blocking d_alloc_parallel() for the filesystems that prime the dcache from readdir, smb, nfs, fuse and ceph, where waiting for a concurrent lookup is pointless. d_duplicate() creates an in-lookup dentry with the name of an existing one for silly-rename and whiteouts. LOOKUP_SHARED tells ->lookup() how the parent is locked so it can drop and retake it. DCACHE_PAR_LOOKUP is tracked by lockdep now with a per filesystem type key, and overlayfs gets its own class since it stacks over itself. And a d_flags bit is reserved for filesystem private use. Also included is Mateusz's fix for the spurious dentry reference cycle on open. __legitimize_path() grabs a reference, do_dentry_open() grabs another and terminate_walk() drops the first. do_dentry_open() consumes the held reference now. Opening the same file read-only on a 20-core VM goes from 4,043,375 to 5,629,378 ops/s in will-it-scale" * tag 'vfs-7.4-rc1.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: VFS: d_duplicate: repair comments to avoid kernel-doc warnings ovl: provide private lockdep class for dentry->dep_map VFS: rename lookup_map to dep_map VFS: per-fs-type lockdep key for dentry in-lookup locking VFS: reserve a d_flags bit for fs-specific usage VFS: add lockdep monitoring of DCACHE_PAR_LOOKUP lock. VFS: Add LOOKUP_SHARED flag. VFS: add d_duplicate() VFS: introduce d_alloc_trylock() VFS: enhance d_splice_alias() to handle hashed dentries VFS: fix various typos in documentation for start_creating start_removing etc fs: avoid spurious dentry ref/unref cycle on open