mirror of
https://github.com/torvalds/linux.git
synced 2026-10-07 19:16:02 +02:00
18fbf5151d
Everything: Total patches: 171 Reviews/patch: 1.83 Reviewed rate: 82% Excluding selftests: Total patches: 149 Reviews/patch: 1.77 Reviewed rate: 80% Excluding selftests and maple_tree: Total patches: 129 Reviews/patch: 1.99 Reviewed rate: 89% Summary of patch series in this merge: - "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous pgoff" (Lorenzo Stoakes): Index MAP_PRIVATE file-backed folios by their anonymous page offset to resolve confusion around reverse mapping for zeroed and CoW'd file-backed memory. Use this new VMA anonymous page offset tracking to eliminate index conflicts and lay the foundation for scalable CoW performance improvements. - "promote mapped executable folios after first usage for MGLRU" (Baolin Wang): Make MGLRU's protection of mapped executable file folios more reliable. Follow the classical LRU's logic, promoting mapped executable file folios after their first usage to give executable code a better chance to stay in memory and improve workload performance. - "mm: vmscan: fix node reclaim ignoring swappiness parameter" (Ridong Chen): Fix per-node proactive reclaim interface's ignoring the swappiness parameter when CONFIG_MEMCG is disabled by consolidating sc_swappiness() into a single function that checks proactive_swappiness regardless of kernel configuration. - "mm/vmscan: reduce lru_lock contention via vmstat-derived scan-balance cost" (Usama Arif): Reduce lru_lock contention in the reclaim path by deriving scan-balance costs from vmstat counters rather than lock-acquired producer updates. Read and decay these cost signals on the reclaim side under a dedicated per-lruvec lock, reducing total LRU lock wait time by over 60% without impacting scan throughput. - "zram: fix zram issues reported by sashiko" (Sergey Senozhatsky): Fix two low-risk zram bugs which Sashiko spotted in drive-by review. - "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's memcg" (Zi Yan): Fix xas_split_alloc() by enabling target folio memcg charging during splits and adding the missing __GFP_ACCOUNT flag for proper XArray node memory accounting. - "selftests/mm: use pattern matching in .gitignore" (Pratyush Mallick): Replace hardcoded binary names in selftests/mm/.gitignore with a generic pattern-matching rule to automatically ignore generated test files and avoid manual updates when adding new tests. - "mm/page_ext: remove pgdat_page_ext_init()" (Sang-Heon Jeon): Make the incompatibility between FLATMEM and NUMA explicit in mm/Kconfig and remove the unused pgdat_page_ext_init() function. - "zram: fix zstd error paths and add parameter validation" (Haoqin Huang): Clean up zram compression backends by removing redundant error cleanup, adding parameter and dictionary validation, auto-prefixing algorithm error logs, and resetting parameters prior to reinitialization. - "zram: fix stale scan bounds after reinitialization" (Longlong Xia): Prevent out-of-bounds slot accesses during concurrent zram resets by moving table scan bound calculations under dev_lock in writeback_store() and read_block_state(). - "add anon mTHP collapse test cases" (Baolin Wang): Extend selftests helper functions to support arbitrary page orders and add new test cases and options for mTHP collapse in khugepaged. - "selftests/mm: Handle unsupported and transient test conditions" (Muhammad Usama Anjum): Update MM selftests to report a SKIP status instead of a failure when required kernel or filesystem features are unsupported, while adding retry logic for transient page migration errors. - "mm/zswap: Fixes and improves the zswap shrink" (Hao Jia): Fix the missing zswap global shrinker when CONFIG_MEMCG is disabled and extend shrink_memcg() to support batch writeback for improved writeback efficiency. - "alloc_tag: introduce IOCTL-based filtering for MAP" (Suren Baghdasaryan): Introduce an IOCTL-based binary interface for memory allocation profiling that enables kernel-side filtering before per-CPU counter aggregation. This eliminates the text-parsing overhead of /proc/allocinfo and provides up to a 20x speedup by transferring only filtered allocation data to userspace. - "better block swap batching and a different take on swap_ops v5" (Christoph Hellwig): Refactor block swap I/O to use swap_iocb for batching instead of single-bio requests and rebase the swap_ops interface, achieving faster swap throughput during kernel builds. - "mm: kmemleak: reduce transient false positives by confirming leaks" (Catalin Marinas): Reduce false-positive kmemleak reports by combining two kmemleak enhancements that add a second confirmation scan and a configurable minimum unreferenced scan count module parameter. - "mm: kmemleak: default min_unref_scans to 2 for verbose kernels" (Breno Leitao): Auto-scanning kernels can generate false-positive memory leak reports on single scans, so this patch defaults min_unref_scans to 2 when CONFIG_DEBUG_KMEMLEAK_VERBOSE is enabled to require a second confirming scan. - "swap_ops updates" (Christoph Hellwig): Batching I/O for synchronous swap devices causes performance regressions and filesystem-based swap suffers from double-indirection overhead. This series resolves both issues by reintroducing per-folio writes for synchronous swap and allowing filesystems to directly export their own swap_ops. - "mm/khugepaged: several cleanups" (Nico Pache): khugepaged accumulated redundant state-checking patterns and outdated comments following mTHP integration. Introduce dedicated helpers for PTE validation and event counting while refreshing the internal documentation. - "maple_tree: lock checking and clean ups" (Liam Howlett): Syzbot reports incorrectly blame memory management exit paths for locking bugs, maple tree erase operations risk allocation failures without gfp flags and internal documentation lacks clarity. Improve lock error detection, update docs, fix race and allocation edge cases and optimize erase allocations using a fallback to GFP_KERNEL | GFP_NOFAIL. -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCao9nJQAKCRDdBJ7gKXxA jk/9AQDlfevYJuSJmzAI8bt8ISG+/TfXMtIZC/MdbHqtQVYWPQD8Cvm3DUZsdGB/ Gloq/HBFuMPgE8p2pwUIthdgnTPNvAc= =c+Nb -----END PGP SIGNATURE----- Merge tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull more MM updates from Andrew Morton: - "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous pgoff" (Lorenzo Stoakes) Index MAP_PRIVATE file-backed folios by their anonymous page offset to resolve confusion around reverse mapping for zeroed and CoW'd file-backed memory. Use this new VMA anonymous page offset tracking to eliminate index conflicts and lay the foundation for scalable CoW performance improvements. - "promote mapped executable folios after first usage for MGLRU" (Baolin Wang) Make MGLRU's protection of mapped executable file folios more reliable. Follow the classical LRU's logic, promoting mapped executable file folios after their first usage to give executable code a better chance to stay in memory and improve workload performance. - "mm: vmscan: fix node reclaim ignoring swappiness parameter" (Ridong Chen) Fix per-node proactive reclaim interface's ignoring the swappiness parameter when CONFIG_MEMCG is disabled by consolidating sc_swappiness() into a single function that checks proactive_swappiness regardless of kernel configuration. - "mm/vmscan: reduce lru_lock contention via vmstat-derived scan-balance cost" (Usama Arif) Reduce lru_lock contention in the reclaim path by deriving scan-balance costs from vmstat counters rather than lock-acquired producer updates. Read and decay these cost signals on the reclaim side under a dedicated per-lruvec lock, reducing total LRU lock wait time by over 60% without impacting scan throughput. - "zram: fix zram issues reported by sashiko" (Sergey Senozhatsky) Fix two low-risk zram bugs which Sashiko spotted in drive-by review. - "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's memcg" (Zi Yan) Fix xas_split_alloc() by enabling target folio memcg charging during splits and adding the missing __GFP_ACCOUNT flag for proper XArray node memory accounting. - "selftests/mm: use pattern matching in .gitignore" (Pratyush Mallick) Replace hardcoded binary names in selftests/mm/.gitignore with a generic pattern-matching rule to automatically ignore generated test files and avoid manual updates when adding new tests. - "mm/page_ext: remove pgdat_page_ext_init()" (Sang-Heon Jeon) Make the incompatibility between FLATMEM and NUMA explicit in mm/Kconfig and remove the unused pgdat_page_ext_init() function. - "zram: fix zstd error paths and add parameter validation" (Haoqin Huang) Clean up zram compression backends by removing redundant error cleanup, adding parameter and dictionary validation, auto-prefixing algorithm error logs, and resetting parameters prior to reinitialization. - "zram: fix stale scan bounds after reinitialization" (Longlong Xia) Prevent out-of-bounds slot accesses during concurrent zram resets by moving table scan bound calculations under dev_lock in writeback_store() and read_block_state(). - "add anon mTHP collapse test cases" (Baolin Wang) Extend selftests helper functions to support arbitrary page orders and add new test cases and options for mTHP collapse in khugepaged. - "selftests/mm: Handle unsupported and transient test conditions" (Muhammad Usama Anjum) Update MM selftests to report a SKIP status instead of a failure when required kernel or filesystem features are unsupported, while adding retry logic for transient page migration errors. - "mm/zswap: Fixes and improves the zswap shrink" (Hao Jia) Fix the missing zswap global shrinker when CONFIG_MEMCG is disabled and extend shrink_memcg() to support batch writeback for improved writeback efficiency. - "alloc_tag: introduce IOCTL-based filtering for MAP" (Suren Baghdasaryan) Introduce an IOCTL-based binary interface for memory allocation profiling that enables kernel-side filtering before per-CPU counter aggregation. This eliminates the text-parsing overhead of /proc/allocinfo and provides up to a 20x speedup by transferring only filtered allocation data to userspace. - "better block swap batching and a different take on swap_ops v5" (Christoph Hellwig) Refactor block swap I/O to use swap_iocb for batching instead of single-bio requests and rebase the swap_ops interface, achieving faster swap throughput during kernel builds. - "mm: kmemleak: reduce transient false positives by confirming leaks" (Catalin Marinas) Reduce false-positive kmemleak reports by combining two kmemleak enhancements that add a second confirmation scan and a configurable minimum unreferenced scan count module parameter. - "mm: kmemleak: default min_unref_scans to 2 for verbose kernels" (Breno Leitao) Auto-scanning kernels can generate false-positive memory leak reports on single scans, so this patch defaults min_unref_scans to 2 when CONFIG_DEBUG_KMEMLEAK_VERBOSE is enabled to require a second confirming scan. - "swap_ops updates" (Christoph Hellwig) Batching I/O for synchronous swap devices causes performance regressions and filesystem-based swap suffers from double-indirection overhead. This series resolves both issues by reintroducing per-folio writes for synchronous swap and allowing filesystems to directly export their own swap_ops. - "mm/khugepaged: several cleanups" (Nico Pache) khugepaged accumulated redundant state-checking patterns and outdated comments following mTHP integration. Introduce dedicated helpers for PTE validation and event counting while refreshing the internal documentation. - "maple_tree: lock checking and clean ups" (Liam Howlett) Syzbot reports incorrectly blame memory management exit paths for locking bugs, maple tree erase operations risk allocation failures without gfp flags and internal documentation lacks clarity. Improve lock error detection, update docs, fix race and allocation edge cases and optimize erase allocations using a fallback to GFP_KERNEL | GFP_NOFAIL. * tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (172 commits) selftests/proc: make proc-maps-race work with READ_IMPLIES_EXEC memcg: move LRU size accounting on reparenting instead of copying it mm/vmscan: fix comment logic in balance_pgdat maple_tree: add helper mas_make_walkable() maple_tree: avoid extra gap calculation maple_tree: fix argument name in header maple_tree: change two GFP flags in tests maple_tree: document erase and allocations better maple_tree: avoid mas_erase() and mtree_erase() failures maple_tree: document that erase may use GFP_KERNEL for allocations maple_tree: catch race in mas_alloc_cyclic() maple_tree: add bulk parent set helper maple_tree: micro optimisation of mas_wr_store_type() maple_tree: optimise mas_wr_node_store() when not in rcu mode maple_tree: use prefetched value in mas_wr_store_type() maple_tree: clarify comments on mas_nomem() maple_tree: drop MAPLE_ALLOC_SLOTS maple_tree: drop dead code from mas_extend_spanning_null() maple_tree: documentation fix maple_tree: add write lock checking with lockdep sequence numbers ...
650 lines
25 KiB
ReStructuredText
650 lines
25 KiB
ReStructuredText
=======
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Locking
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=======
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The text below describes the locking rules for VFS-related methods.
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It is (believed to be) up-to-date. *Please*, if you change anything in
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prototypes or locking protocols - update this file. And update the relevant
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instances in the tree, don't leave that to maintainers of filesystems/devices/
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etc. At the very least, put the list of dubious cases in the end of this file.
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Don't turn it into log - maintainers of out-of-the-tree code are supposed to
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be able to use diff(1).
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Thing currently missing here: socket operations. Alexey?
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dentry_operations
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=================
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prototypes::
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int (*d_revalidate)(struct inode *, const struct qstr *,
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struct dentry *, unsigned int);
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int (*d_weak_revalidate)(struct dentry *, unsigned int);
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int (*d_hash)(const struct dentry *, struct qstr *);
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int (*d_compare)(const struct dentry *,
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unsigned int, const char *, const struct qstr *);
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int (*d_delete)(struct dentry *);
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int (*d_init)(struct dentry *);
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void (*d_release)(struct dentry *);
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void (*d_iput)(struct dentry *, struct inode *);
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char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
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struct vfsmount *(*d_automount)(struct path *path);
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int (*d_manage)(const struct path *, bool);
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struct dentry *(*d_real)(struct dentry *, enum d_real_type type);
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bool (*d_unalias_trylock)(const struct dentry *);
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void (*d_unalias_unlock)(const struct dentry *);
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locking rules:
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================== =========== ======== ============== ========
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ops rename_lock ->d_lock may block rcu-walk
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================== =========== ======== ============== ========
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d_revalidate: no no yes (ref-walk) maybe
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d_weak_revalidate: no no yes no
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d_hash no no no maybe
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d_compare: yes no no maybe
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d_delete: no yes no no
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d_init: no no yes no
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d_release: no no yes no
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d_prune: no yes no no
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d_iput: no no yes no
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d_dname: no no no no
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d_automount: no no yes no
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d_manage: no no yes (ref-walk) maybe
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d_real no no yes no
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d_unalias_trylock yes no no no
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d_unalias_unlock yes no no no
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================== =========== ======== ============== ========
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inode_operations
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================
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prototypes::
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int (*create) (struct mnt_idmap *, struct inode *,struct dentry *,umode_t);
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struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
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int (*link) (struct dentry *,struct inode *,struct dentry *);
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int (*unlink) (struct inode *,struct dentry *);
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int (*symlink) (struct mnt_idmap *, struct inode *,struct dentry *,const char *);
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struct dentry *(*mkdir) (struct mnt_idmap *, struct inode *,struct dentry *,umode_t);
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int (*rmdir) (struct inode *,struct dentry *);
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int (*mknod) (struct mnt_idmap *, struct inode *,struct dentry *,umode_t,dev_t);
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int (*rename) (struct mnt_idmap *, struct inode *, struct dentry *,
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struct inode *, struct dentry *, unsigned int);
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int (*readlink) (struct dentry *, char __user *,int);
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const char *(*get_link) (struct dentry *, struct inode *, struct delayed_call *);
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void (*truncate) (struct inode *);
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int (*permission) (struct mnt_idmap *, struct inode *, int, unsigned int);
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struct posix_acl * (*get_inode_acl)(struct inode *, int, bool);
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int (*setattr) (struct mnt_idmap *, struct dentry *, struct iattr *);
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int (*getattr) (struct mnt_idmap *, const struct path *, struct kstat *, u32, unsigned int);
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ssize_t (*listxattr) (struct dentry *, char *, size_t);
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int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
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void (*update_time)(struct inode *inode, enum fs_update_time type,
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int flags);
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void (*sync_lazytime)(struct inode *inode);
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int (*atomic_open)(struct inode *, struct dentry *,
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struct file *, unsigned open_flag,
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umode_t create_mode);
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int (*tmpfile) (struct mnt_idmap *, struct inode *,
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struct file *, umode_t);
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int (*fileattr_set)(struct mnt_idmap *idmap,
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struct dentry *dentry, struct file_kattr *fa);
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int (*fileattr_get)(struct dentry *dentry, struct file_kattr *fa);
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struct posix_acl * (*get_acl)(struct mnt_idmap *, struct dentry *, int);
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struct offset_ctx *(*get_offset_ctx)(struct inode *inode);
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locking rules:
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all may block
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============== ==================================================
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ops i_rwsem(inode)
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============== ==================================================
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lookup: shared
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create: exclusive
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link: exclusive (both)
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mknod: exclusive
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symlink: exclusive
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mkdir: exclusive
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unlink: exclusive (both)
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rmdir: exclusive (both)(see below)
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rename: exclusive (both parents, some children) (see below)
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readlink: no
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get_link: no
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setattr: exclusive
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permission: no (may not block if called in rcu-walk mode)
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get_inode_acl: no
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get_acl: no
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getattr: no
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listxattr: no
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fiemap: no
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update_time: no
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sync_lazytime: no
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atomic_open: shared (exclusive if O_CREAT is set in open flags)
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tmpfile: no
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fileattr_get: no or exclusive
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fileattr_set: exclusive
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get_offset_ctx no
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============== ==================================================
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Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem
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exclusive on victim.
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cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
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->unlink() and ->rename() have ->i_rwsem exclusive on all non-directories
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involved.
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->rename() has ->i_rwsem exclusive on any subdirectory that changes parent.
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See Documentation/filesystems/directory-locking.rst for more detailed discussion
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of the locking scheme for directory operations.
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xattr_handler operations
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========================
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prototypes::
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bool (*list)(struct dentry *dentry);
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int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
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struct inode *inode, const char *name, void *buffer,
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size_t size);
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int (*set)(const struct xattr_handler *handler,
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struct mnt_idmap *idmap,
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struct dentry *dentry, struct inode *inode, const char *name,
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const void *buffer, size_t size, int flags);
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locking rules:
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all may block
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===== ==============
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ops i_rwsem(inode)
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===== ==============
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list: no
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get: no
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set: exclusive
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===== ==============
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super_operations
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================
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prototypes::
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struct inode *(*alloc_inode)(struct super_block *sb);
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void (*free_inode)(struct inode *);
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void (*destroy_inode)(struct inode *);
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void (*dirty_inode) (struct inode *, int flags);
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int (*write_inode) (struct inode *, struct writeback_control *wbc);
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int (*drop_inode) (struct inode *);
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void (*evict_inode) (struct inode *);
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void (*put_super) (struct super_block *);
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int (*sync_fs)(struct super_block *sb, int wait);
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int (*freeze_fs) (struct super_block *);
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int (*unfreeze_fs) (struct super_block *);
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int (*statfs) (struct dentry *, struct kstatfs *);
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void (*umount_begin) (struct super_block *);
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int (*show_options)(struct seq_file *, struct dentry *);
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ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
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ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
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locking rules:
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All may block [not true, see below]
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====================== ============ ========================
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ops s_umount note
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====================== ============ ========================
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alloc_inode:
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free_inode: called from RCU callback
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destroy_inode:
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dirty_inode:
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write_inode:
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drop_inode: !!!inode->i_lock!!!
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evict_inode:
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put_super: write
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sync_fs: read
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freeze_fs: write
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unfreeze_fs: write
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statfs: maybe(read) (see below)
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umount_begin: no
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show_options: no (namespace_sem)
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quota_read: no (see below)
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quota_write: no (see below)
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====================== ============ ========================
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->statfs() has s_umount (shared) when called by ustat(2) (native or
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compat), but that's an accident of bad API; s_umount is used to pin
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the superblock down when we only have dev_t given us by userland to
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identify the superblock. Everything else (statfs(), fstatfs(), etc.)
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doesn't hold it when calling ->statfs() - superblock is pinned down
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by resolving the pathname passed to syscall.
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->quota_read() and ->quota_write() functions are both guaranteed to
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be the only ones operating on the quota file by the quota code (via
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dqio_sem) (unless an admin really wants to screw up something and
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writes to quota files with quotas on). For other details about locking
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see also dquot_operations section.
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file_system_type
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================
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prototypes::
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void (*kill_sb) (struct super_block *);
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locking rules:
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======= =========
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ops may block
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======= =========
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kill_sb yes
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======= =========
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->kill_sb() takes a write-locked superblock, does all shutdown work on it,
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unlocks and drops the reference.
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address_space_operations
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========================
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prototypes::
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int (*read_folio)(struct file *, struct folio *);
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int (*writepages)(struct address_space *, struct writeback_control *);
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bool (*dirty_folio)(struct address_space *, struct folio *folio);
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void (*readahead)(struct readahead_control *);
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int (*write_begin)(const struct kiocb *, struct address_space *mapping,
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loff_t pos, unsigned len,
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struct folio **foliop, void **fsdata);
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int (*write_end)(const struct kiocb *, struct address_space *mapping,
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loff_t pos, unsigned len, unsigned copied,
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struct folio *folio, void *fsdata);
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sector_t (*bmap)(struct address_space *, sector_t);
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void (*invalidate_folio) (struct folio *, size_t start, size_t len);
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bool (*release_folio)(struct folio *, gfp_t);
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void (*free_folio)(struct folio *);
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int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
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int (*migrate_folio)(struct address_space *, struct folio *dst,
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struct folio *src, enum migrate_mode);
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int (*launder_folio)(struct folio *);
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bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count);
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int (*error_remove_folio)(struct address_space *, struct folio *);
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int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span)
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int (*swap_deactivate)(struct file *);
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locking rules:
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All except dirty_folio and free_folio may block
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====================== ======================== ========= ===============
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ops folio locked i_rwsem invalidate_lock
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====================== ======================== ========= ===============
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read_folio: yes, unlocks shared
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writepages:
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dirty_folio: maybe
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readahead: yes, unlocks shared
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write_begin: locks the folio exclusive
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write_end: yes, unlocks exclusive
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bmap:
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invalidate_folio: yes exclusive
|
|
release_folio: yes
|
|
free_folio: yes
|
|
direct_IO:
|
|
migrate_folio: yes (both)
|
|
launder_folio: yes
|
|
is_partially_uptodate: yes
|
|
error_remove_folio: yes
|
|
swap_activate: no
|
|
swap_deactivate: no
|
|
====================== ======================== ========= ===============
|
|
|
|
->write_begin(), ->write_end() and ->read_folio() may be called from
|
|
the request handler (/dev/loop).
|
|
|
|
->read_folio() unlocks the folio, either synchronously or via I/O
|
|
completion.
|
|
|
|
->readahead() unlocks the folios that I/O is attempted on like ->read_folio().
|
|
|
|
->writepages() is used for periodic writeback and for syscall-initiated
|
|
sync operations. The address_space should start I/O against at least
|
|
``*nr_to_write`` pages. ``*nr_to_write`` must be decremented for each page
|
|
which is written. The address_space implementation may write more (or less)
|
|
pages than ``*nr_to_write`` asks for, but it should try to be reasonably close.
|
|
If nr_to_write is NULL, all dirty pages must be written.
|
|
|
|
writepages should _only_ write pages which are present in
|
|
mapping->i_pages.
|
|
|
|
->dirty_folio() is called from various places in the kernel when
|
|
the target folio is marked as needing writeback. The folio cannot be
|
|
truncated because either the caller holds the folio lock, or the caller
|
|
has found the folio while holding the page table lock which will block
|
|
truncation.
|
|
|
|
->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some
|
|
filesystems and by the swapper. The latter will eventually go away. Please,
|
|
keep it that way and don't breed new callers.
|
|
|
|
->invalidate_folio() is called when the filesystem must attempt to drop
|
|
some or all of the buffers from the page when it is being truncated. It
|
|
returns zero on success. The filesystem must exclusively acquire
|
|
invalidate_lock before invalidating page cache in truncate / hole punch
|
|
path (and thus calling into ->invalidate_folio) to block races between page
|
|
cache invalidation and page cache filling functions (fault, read, ...).
|
|
|
|
->release_folio() is called when the MM wants to make a change to the
|
|
folio that would invalidate the filesystem's private data. For example,
|
|
it may be about to be removed from the address_space or split. The folio
|
|
is locked and not under writeback. It may be dirty. The gfp parameter
|
|
is not usually used for allocation, but rather to indicate what the
|
|
filesystem may do to attempt to free the private data. The filesystem may
|
|
return false to indicate that the folio's private data cannot be freed.
|
|
If it returns true, it should have already removed the private data from
|
|
the folio. If a filesystem does not provide a ->release_folio method,
|
|
the pagecache will assume that private data is buffer_heads and call
|
|
try_to_free_buffers().
|
|
|
|
->free_folio() is called when the kernel has dropped the folio
|
|
from the page cache.
|
|
|
|
->launder_folio() may be called prior to releasing a folio if
|
|
it is still found to be dirty. It returns zero if the folio was successfully
|
|
cleaned, or an error value if not. Note that in order to prevent the folio
|
|
getting mapped back in and redirtied, it needs to be kept locked
|
|
across the entire operation.
|
|
|
|
->swap_activate() will be called to prepare the given file for swap. It
|
|
should perform any validation and preparation necessary to ensure that
|
|
writes can be performed with minimal memory allocation. It should call
|
|
add_swap_extent(), or the helper iomap_swapfile_activate(), and return
|
|
the number of extents added. If IO should be submitted through
|
|
the file system it should call swap_fs_activate, otherwise IO will be
|
|
submitted directly to the block device ``sis->bdev``.
|
|
|
|
->swap_deactivate() will be called in the sys_swapoff()
|
|
path after ->swap_activate() returned success.
|
|
|
|
file_lock_operations
|
|
====================
|
|
|
|
prototypes::
|
|
|
|
void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
|
|
void (*fl_release_private)(struct file_lock *);
|
|
|
|
|
|
locking rules:
|
|
|
|
=================== ============= =========
|
|
ops inode->i_lock may block
|
|
=================== ============= =========
|
|
fl_copy_lock: yes no
|
|
fl_release_private: maybe maybe[1]_
|
|
=================== ============= =========
|
|
|
|
.. [1]:
|
|
->fl_release_private for flock or POSIX locks is currently allowed
|
|
to block. Leases however can still be freed while the i_lock is held and
|
|
so fl_release_private called on a lease should not block.
|
|
|
|
lock_manager_operations
|
|
=======================
|
|
|
|
prototypes::
|
|
|
|
void (*lm_notify)(struct file_lock *); /* unblock callback */
|
|
int (*lm_grant)(struct file_lock *, struct file_lock *, int);
|
|
void (*lm_break)(struct file_lock *); /* break_lease callback */
|
|
int (*lm_change)(struct file_lock **, int);
|
|
bool (*lm_breaker_owns_lease)(struct file_lock *);
|
|
bool (*lm_lock_expirable)(struct file_lock *);
|
|
void (*lm_expire_lock)(void);
|
|
bool (*lm_breaker_timedout)(struct file_lease *);
|
|
|
|
locking rules:
|
|
|
|
====================== ============= ================= =========
|
|
ops flc_lock blocked_lock_lock may block
|
|
====================== ============= ================= =========
|
|
lm_notify: no yes no
|
|
lm_grant: no no no
|
|
lm_break: yes no no
|
|
lm_change yes no no
|
|
lm_breaker_owns_lease: yes no no
|
|
lm_lock_expirable yes no no
|
|
lm_expire_lock no no yes
|
|
lm_open_conflict yes no no
|
|
lm_breaker_timedout yes no no
|
|
====================== ============= ================= =========
|
|
|
|
block_device_operations
|
|
=======================
|
|
prototypes::
|
|
|
|
int (*open) (struct block_device *, fmode_t);
|
|
int (*release) (struct gendisk *, fmode_t);
|
|
int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
|
|
int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
|
|
int (*direct_access) (struct block_device *, sector_t, void **,
|
|
unsigned long *);
|
|
void (*unlock_native_capacity) (struct gendisk *);
|
|
int (*getgeo)(struct gendisk *, struct hd_geometry *);
|
|
void (*swap_slot_free_notify) (struct block_device *, unsigned long);
|
|
|
|
locking rules:
|
|
|
|
======================= ===================
|
|
ops open_mutex
|
|
======================= ===================
|
|
open: yes
|
|
release: yes
|
|
ioctl: no
|
|
compat_ioctl: no
|
|
direct_access: no
|
|
unlock_native_capacity: no
|
|
getgeo: no
|
|
swap_slot_free_notify: no (see below)
|
|
======================= ===================
|
|
|
|
swap_slot_free_notify is called with swap_lock and sometimes the page lock
|
|
held.
|
|
|
|
|
|
file_operations
|
|
===============
|
|
|
|
prototypes::
|
|
|
|
loff_t (*llseek) (struct file *, loff_t, int);
|
|
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
|
|
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
|
|
ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
|
|
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
|
|
int (*iopoll) (struct kiocb *kiocb, bool spin);
|
|
int (*iterate_shared) (struct file *, struct dir_context *);
|
|
__poll_t (*poll) (struct file *, struct poll_table_struct *);
|
|
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
|
|
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
|
|
int (*mmap) (struct file *, struct vm_area_struct *);
|
|
int (*open) (struct inode *, struct file *);
|
|
int (*flush) (struct file *);
|
|
int (*release) (struct inode *, struct file *);
|
|
int (*fsync) (struct file *, loff_t start, loff_t end, int datasync);
|
|
int (*fasync) (int, struct file *, int);
|
|
int (*lock) (struct file *, int, struct file_lock *);
|
|
unsigned long (*get_unmapped_area)(struct file *, unsigned long,
|
|
unsigned long, unsigned long, unsigned long);
|
|
int (*check_flags)(int);
|
|
int (*flock) (struct file *, int, struct file_lock *);
|
|
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *,
|
|
size_t, unsigned int);
|
|
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
|
|
size_t, unsigned int);
|
|
int (*setlease)(struct file *, long, struct file_lock **, void **);
|
|
long (*fallocate)(struct file *, int, loff_t, loff_t);
|
|
void (*show_fdinfo)(struct seq_file *m, struct file *f);
|
|
unsigned (*mmap_capabilities)(struct file *);
|
|
ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
|
|
loff_t, size_t, unsigned int);
|
|
loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
|
|
struct file *file_out, loff_t pos_out,
|
|
loff_t len, unsigned int remap_flags);
|
|
int (*fadvise)(struct file *, loff_t, loff_t, int);
|
|
|
|
locking rules:
|
|
All may block.
|
|
|
|
->llseek() locking has moved from llseek to the individual llseek
|
|
implementations. If your fs is not using generic_file_llseek, you
|
|
need to acquire and release the appropriate locks in your ->llseek().
|
|
For many filesystems, it is probably safe to acquire the inode
|
|
mutex or just to use i_size_read() instead.
|
|
Note: this does not protect the file->f_pos against concurrent modifications
|
|
since this is something the userspace has to take care about.
|
|
|
|
->iterate_shared() is called with i_rwsem held for reading, and with the
|
|
file f_pos_lock held exclusively
|
|
|
|
->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags.
|
|
Most instances call fasync_helper(), which does that maintenance, so it's
|
|
not normally something one needs to worry about. Return values > 0 will be
|
|
mapped to zero in the VFS layer.
|
|
|
|
->readdir() and ->ioctl() on directories must be changed. Ideally we would
|
|
move ->readdir() to inode_operations and use a separate method for directory
|
|
->ioctl() or kill the latter completely. One of the problems is that for
|
|
anything that resembles union-mount we won't have a struct file for all
|
|
components. And there are other reasons why the current interface is a mess...
|
|
|
|
->read on directories probably must go away - we should just enforce -EISDIR
|
|
in sys_read() and friends.
|
|
|
|
->setlease operations should call generic_setlease() before or after setting
|
|
the lease within the individual filesystem to record the result of the
|
|
operation
|
|
|
|
->fallocate implementation must be really careful to maintain page cache
|
|
consistency when punching holes or performing other operations that invalidate
|
|
page cache contents. Usually the filesystem needs to call
|
|
truncate_inode_pages_range() to invalidate relevant range of the page cache.
|
|
However the filesystem usually also needs to update its internal (and on disk)
|
|
view of file offset -> disk block mapping. Until this update is finished, the
|
|
filesystem needs to block page faults and reads from reloading now-stale page
|
|
cache contents from the disk. Since VFS acquires mapping->invalidate_lock in
|
|
shared mode when loading pages from disk (filemap_fault(), filemap_read(),
|
|
readahead paths), the fallocate implementation must take the invalidate_lock to
|
|
prevent reloading.
|
|
|
|
->copy_file_range and ->remap_file_range implementations need to serialize
|
|
against modifications of file data while the operation is running. For
|
|
blocking changes through write(2) and similar operations inode->i_rwsem can be
|
|
used. To block changes to file contents via a memory mapping during the
|
|
operation, the filesystem must take mapping->invalidate_lock to coordinate
|
|
with ->page_mkwrite.
|
|
|
|
dquot_operations
|
|
================
|
|
|
|
prototypes::
|
|
|
|
int (*write_dquot) (struct dquot *);
|
|
int (*acquire_dquot) (struct dquot *);
|
|
int (*release_dquot) (struct dquot *);
|
|
int (*mark_dirty) (struct dquot *);
|
|
int (*write_info) (struct super_block *, int);
|
|
|
|
These operations are intended to be more or less wrapping functions that ensure
|
|
a proper locking wrt the filesystem and call the generic quota operations.
|
|
|
|
What filesystem should expect from the generic quota functions:
|
|
|
|
============== ============ =========================
|
|
ops FS recursion Held locks when called
|
|
============== ============ =========================
|
|
write_dquot: yes dqonoff_sem or dqptr_sem
|
|
acquire_dquot: yes dqonoff_sem or dqptr_sem
|
|
release_dquot: yes dqonoff_sem or dqptr_sem
|
|
mark_dirty: no -
|
|
write_info: yes dqonoff_sem
|
|
============== ============ =========================
|
|
|
|
FS recursion means calling ->quota_read() and ->quota_write() from superblock
|
|
operations.
|
|
|
|
More details about quota locking can be found in fs/quota/dquot.c.
|
|
|
|
vm_operations_struct
|
|
====================
|
|
|
|
prototypes::
|
|
|
|
void (*open)(struct vm_area_struct *);
|
|
void (*close)(struct vm_area_struct *);
|
|
vm_fault_t (*fault)(struct vm_fault *);
|
|
vm_fault_t (*huge_fault)(struct vm_fault *, unsigned int order);
|
|
vm_fault_t (*map_pages)(struct vm_fault *, pgoff_t start, pgoff_t end);
|
|
vm_fault_t (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *);
|
|
vm_fault_t (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *);
|
|
int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
|
|
|
|
locking rules:
|
|
|
|
============= ========== ===========================
|
|
ops mmap_lock PageLocked(page)
|
|
============= ========== ===========================
|
|
open: write
|
|
close: read/write
|
|
fault: read can return with page locked
|
|
huge_fault: maybe-read
|
|
map_pages: maybe-read
|
|
page_mkwrite: read can return with page locked
|
|
pfn_mkwrite: read
|
|
access: read
|
|
============= ========== ===========================
|
|
|
|
->fault() is called when a previously not present pte is about to be faulted
|
|
in. The filesystem must find and return the page associated with the passed in
|
|
"pgoff" in the vm_fault structure. If it is possible that the page may be
|
|
truncated and/or invalidated, then the filesystem must lock invalidate_lock,
|
|
then ensure the page is not already truncated (invalidate_lock will block
|
|
subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
|
|
locked. The VM will unlock the page.
|
|
|
|
->huge_fault() is called when there is no PUD or PMD entry present. This
|
|
gives the filesystem the opportunity to install a PUD or PMD sized page.
|
|
Filesystems can also use the ->fault method to return a PMD sized page,
|
|
so implementing this function may not be necessary. In particular,
|
|
filesystems should not call filemap_fault() from ->huge_fault().
|
|
The mmap_lock may not be held when this method is called.
|
|
|
|
->map_pages() is called when VM asks to map easy accessible pages.
|
|
Filesystem should find and map pages associated with offsets from "start_pgoff"
|
|
till "end_pgoff". ->map_pages() is called with the RCU lock held and must
|
|
not block. If it's not possible to reach a page without blocking,
|
|
filesystem should skip it. Filesystem should use set_pte_range() to setup
|
|
page table entry. Pointer to entry associated with the page is passed in
|
|
"pte" field in vm_fault structure. Pointers to entries for other offsets
|
|
should be calculated relative to "pte".
|
|
|
|
->page_mkwrite() is called when a previously read-only pte is about to become
|
|
writeable. The filesystem again must ensure that there are no
|
|
truncate/invalidate races or races with operations such as ->remap_file_range
|
|
or ->copy_file_range, and then return with the page locked. Usually
|
|
mapping->invalidate_lock is suitable for proper serialization. If the page has
|
|
been truncated, the filesystem should not look up a new page like the ->fault()
|
|
handler, but simply return with VM_FAULT_NOPAGE, which will cause the VM to
|
|
retry the fault.
|
|
|
|
->pfn_mkwrite() is the same as page_mkwrite but when the pte is
|
|
VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is
|
|
VM_FAULT_NOPAGE. Or one of the VM_FAULT_ERROR types. The default behavior
|
|
after this call is to make the pte read-write, unless pfn_mkwrite returns
|
|
an error.
|
|
|
|
->access() is called when get_user_pages() fails in
|
|
access_process_vm(), typically used to debug a process through
|
|
/proc/pid/mem or ptrace. This function is needed only for
|
|
VM_IO | VM_PFNMAP VMAs.
|
|
|
|
--------------------------------------------------------------------------------
|
|
|
|
Dubious stuff
|
|
|
|
(if you break something or notice that it is broken and do not fix it yourself
|
|
- at least put it here)
|