Merge tag 'vfs-7.0-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull misc vfs updates from Christian Brauner:
 "This contains a mix of VFS cleanups, performance improvements, API
  fixes, documentation, and a deprecation notice.

  Scalability and performance:

   - Rework pid allocation to only take pidmap_lock once instead of
     twice during alloc_pid(), improving thread creation/teardown
     throughput by 10-16% depending on false-sharing luck. Pad the
     namespace refcount to reduce false-sharing

   - Track file lock presence via a flag in ->i_opflags instead of
     reading ->i_flctx, avoiding false-sharing with ->i_readcount on
     open/close hot paths. Measured 4-16% improvement on 24-core
     open-in-a-loop benchmarks

   - Use a consume fence in locks_inode_context() to match the
     store-release/load-consume idiom, eliminating a hardware fence on
     some architectures

   - Annotate cdev_lock with __cacheline_aligned_in_smp to prevent
     false-sharing

   - Remove a redundant DCACHE_MANAGED_DENTRY check in
     __follow_mount_rcu() that never fires since the caller already
     verifies it, eliminating a 100% mispredicted branch

   - Fix a 100% mispredicted likely() in devcgroup_inode_permission()
     that became wrong after a prior code reorder

  Bug fixes and correctness:

   - Make insert_inode_locked() wait for inode destruction instead of
     skipping, fixing a corner case where two matching inodes could
     exist in the hash

   - Move f_mode initialization before file_ref_init() in alloc_file()
     to respect the SLAB_TYPESAFE_BY_RCU ordering contract

   - Add a WARN_ON_ONCE guard in try_to_free_buffers() for folios with
     no buffers attached, preventing a null pointer dereference when
     AS_RELEASE_ALWAYS is set but no release_folio op exists

   - Fix select restart_block to store end_time as timespec64, avoiding
     truncation of tv_sec on 32-bit architectures

   - Make dump_inode() use get_kernel_nofault() to safely access inode
     and superblock fields, matching the dump_mapping() pattern

  API modernization:

   - Make posix_acl_to_xattr() allocate the buffer internally since
     every single caller was doing it anyway. Reduces boilerplate and
     unnecessary error checking across ~15 filesystems

   - Replace deprecated simple_strtoul() with kstrtoul() for the
     ihash_entries, dhash_entries, mhash_entries, and mphash_entries
     boot parameters, adding proper error handling

   - Convert chardev code to use guard(mutex) and __free(kfree) cleanup
     patterns

   - Replace min_t() with min() or umin() in VFS code to avoid silently
     truncating unsigned long to unsigned int

   - Gate LOOKUP_RCU assertions behind CONFIG_DEBUG_VFS since callers
     already check the flag

  Deprecation:

   - Begin deprecating legacy BSD process accounting (acct(2)). The
     interface has numerous footguns and better alternatives exist
     (eBPF)

  Documentation:

   - Fix and complete kernel-doc for struct export_operations, removing
     duplicated documentation between ReST and source

   - Fix kernel-doc warnings for __start_dirop() and ilookup5_nowait()

  Testing:

   - Add a kunit test for initramfs cpio handling of entries with
     filesize > PATH_MAX

  Misc:

   - Add missing <linux/init_task.h> include in fs_struct.c"

* tag 'vfs-7.0-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (28 commits)
  posix_acl: make posix_acl_to_xattr() alloc the buffer
  fs: make insert_inode_locked() wait for inode destruction
  initramfs_test: kunit test for cpio.filesize > PATH_MAX
  fs: improve dump_inode() to safely access inode fields
  fs: add <linux/init_task.h> for 'init_fs'
  docs: exportfs: Use source code struct documentation
  fs: move initializing f_mode before file_ref_init()
  exportfs: Complete kernel-doc for struct export_operations
  exportfs: Mark struct export_operations functions at kernel-doc
  exportfs: Fix kernel-doc output for get_name()
  acct(2): begin the deprecation of legacy BSD process accounting
  device_cgroup: remove branch hint after code refactor
  VFS: fix __start_dirop() kernel-doc warnings
  fs: Describe @isnew parameter in ilookup5_nowait()
  fs/namei: Remove redundant DCACHE_MANAGED_DENTRY check in __follow_mount_rcu
  fs: only assert on LOOKUP_RCU when built with CONFIG_DEBUG_VFS
  select: store end_time as timespec64 in restart block
  chardev: Switch to guard(mutex) and __free(kfree)
  namespace: Replace simple_strtoul with kstrtoul to parse boot params
  dcache: Replace simple_strtoul with kstrtoul in set_dhash_entries
  ...

7 files changed, 47 insertions, 20 deletions

diff --git a/include/linux/device_cgroup.h b/include/linux/device_cgroup.h
index 0864773a57e8..822085bc2d20 100644
--- a/include/linux/device_cgroup.h
+++ b/include/linux/device_cgroup.h
@@ -21,7 +21,7 @@ static inline int devcgroup_inode_permission(struct inode *inode, int mask)
 	if (likely(!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode)))
 		return 0;
 
-	if (likely(!inode->i_rdev))
+	if (!inode->i_rdev)
 		return 0;
 
 	if (S_ISBLK(inode->i_mode))
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index f0cf2714ec52..262e24d83313 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -201,9 +201,9 @@ struct handle_to_path_ctx {
  * @commit_metadata: commit metadata changes to stable storage
  *
  * See Documentation/filesystems/nfs/exporting.rst for details on how to use
- * this interface correctly.
+ * this interface correctly and the definition of the flags.
  *
- * encode_fh:
+ * @encode_fh:
  *    @encode_fh should store in the file handle fragment @fh (using at most
  *    @max_len bytes) information that can be used by @decode_fh to recover the
  *    file referred to by the &struct dentry @de.  If @flag has CONNECTABLE bit
@@ -215,7 +215,7 @@ struct handle_to_path_ctx {
  *    greater than @max_len*4 bytes). On error @max_len contains the minimum
  *    size(in 4 byte unit) needed to encode the file handle.
  *
- * fh_to_dentry:
+ * @fh_to_dentry:
  *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
  *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
  *    to the same file that the file handle fragment refers to.  If it cannot,
@@ -227,31 +227,44 @@ struct handle_to_path_ctx {
  *    created with d_alloc_root.  The caller can then find any other extant
  *    dentries by following the d_alias links.
  *
- * fh_to_parent:
+ * @fh_to_parent:
  *    Same as @fh_to_dentry, except that it returns a pointer to the parent
  *    dentry if it was encoded into the filehandle fragment by @encode_fh.
  *
- * get_name:
+ * @get_name:
  *    @get_name should find a name for the given @child in the given @parent
  *    directory.  The name should be stored in the @name (with the
- *    understanding that it is already pointing to a %NAME_MAX+1 sized
+ *    understanding that it is already pointing to a %NAME_MAX + 1 sized
  *    buffer.   get_name() should return %0 on success, a negative error code
  *    or error.  @get_name will be called without @parent->i_rwsem held.
  *
- * get_parent:
+ * @get_parent:
  *    @get_parent should find the parent directory for the given @child which
  *    is also a directory.  In the event that it cannot be found, or storage
  *    space cannot be allocated, a %ERR_PTR should be returned.
  *
- * permission:
+ * @permission:
  *    Allow filesystems to specify a custom permission function.
  *
- * open:
+ * @open:
  *    Allow filesystems to specify a custom open function.
  *
- * commit_metadata:
+ * @commit_metadata:
  *    @commit_metadata should commit metadata changes to stable storage.
  *
+ * @get_uuid:
+ *    Get a filesystem unique signature exposed to clients.
+ *
+ * @map_blocks:
+ *    Map and, if necessary, allocate blocks for a layout.
+ *
+ * @commit_blocks:
+ *    Commit blocks in a layout once the client is done with them.
+ *
+ * @flags:
+ *    Allows the filesystem to communicate to nfsd that it may want to do things
+ *    differently when dealing with it.
+ *
  * Locking rules:
  *    get_parent is called with child->d_inode->i_rwsem down
  *    get_name is not (which is possibly inconsistent)
diff --git a/include/linux/filelock.h b/include/linux/filelock.h
index 2f5e5588ee07..d2c9740e26a8 100644
--- a/include/linux/filelock.h
+++ b/include/linux/filelock.h
@@ -242,7 +242,14 @@ bool locks_owner_has_blockers(struct file_lock_context *flctx,
 static inline struct file_lock_context *
 locks_inode_context(const struct inode *inode)
 {
-	return smp_load_acquire(&inode->i_flctx);
+	/*
+	 * Paired with smp_store_release in locks_get_lock_context().
+	 *
+	 * Ensures ->i_flctx will be visible if we spotted the flag.
+	 */
+	if (likely(!(smp_load_acquire(&inode->i_opflags) & IOP_FLCTX)))
+		return NULL;
+	return READ_ONCE(inode->i_flctx);
 }
 
 #else /* !CONFIG_FILE_LOCKING */
@@ -469,7 +476,7 @@ static inline int break_lease(struct inode *inode, unsigned int mode)
 	 * could end up racing with tasks trying to set a new lease on this
 	 * file.
 	 */
-	flctx = READ_ONCE(inode->i_flctx);
+	flctx = locks_inode_context(inode);
 	if (!flctx)
 		return 0;
 	smp_mb();
@@ -488,7 +495,7 @@ static inline int break_deleg(struct inode *inode, unsigned int flags)
 	 * could end up racing with tasks trying to set a new lease on this
 	 * file.
 	 */
-	flctx = READ_ONCE(inode->i_flctx);
+	flctx = locks_inode_context(inode);
 	if (!flctx)
 		return 0;
 	smp_mb();
@@ -533,8 +540,11 @@ static inline int break_deleg_wait(struct delegated_inode *di)
 
 static inline int break_layout(struct inode *inode, bool wait)
 {
+	struct file_lock_context *flctx;
+
 	smp_mb();
-	if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease)) {
+	flctx = locks_inode_context(inode);
+	if (flctx && !list_empty_careful(&flctx->flc_lease)) {
 		unsigned int flags = LEASE_BREAK_LAYOUT;
 
 		if (!wait)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ca31bc9308a3..73911f961c7e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -631,6 +631,7 @@ is_uncached_acl(struct posix_acl *acl)
 #define IOP_MGTIME		0x0020
 #define IOP_CACHED_LINK		0x0040
 #define IOP_FASTPERM_MAY_EXEC	0x0080
+#define IOP_FLCTX		0x0100
 
 /*
  * Inode state bits.  Protected by inode->i_lock
diff --git a/include/linux/ns/ns_common_types.h b/include/linux/ns/ns_common_types.h
index b332b019b29c..0014fbc1c626 100644
--- a/include/linux/ns/ns_common_types.h
+++ b/include/linux/ns/ns_common_types.h
@@ -108,11 +108,13 @@ extern const struct proc_ns_operations utsns_operations;
  * @ns_tree: namespace tree nodes and active reference count
  */
 struct ns_common {
+	struct {
+		refcount_t __ns_ref; /* do not use directly */
+	} ____cacheline_aligned_in_smp;
 	u32 ns_type;
 	struct dentry *stashed;
 	const struct proc_ns_operations *ops;
 	unsigned int inum;
-	refcount_t __ns_ref; /* do not use directly */
 	union {
 		struct ns_tree;
 		struct rcu_head ns_rcu;
diff --git a/include/linux/posix_acl_xattr.h b/include/linux/posix_acl_xattr.h
index e86f3b731da2..9e1892525eac 100644
--- a/include/linux/posix_acl_xattr.h
+++ b/include/linux/posix_acl_xattr.h
@@ -44,8 +44,9 @@ posix_acl_from_xattr(struct user_namespace *user_ns, const void *value,
 }
 #endif
 
-int posix_acl_to_xattr(struct user_namespace *user_ns,
-		       const struct posix_acl *acl, void *buffer, size_t size);
+extern void *posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
+				size_t *sizep, gfp_t gfp);
+
 static inline const char *posix_acl_xattr_name(int type)
 {
 	switch (type) {
diff --git a/include/linux/restart_block.h b/include/linux/restart_block.h
index 67d2bf579942..9b262109726d 100644
--- a/include/linux/restart_block.h
+++ b/include/linux/restart_block.h
@@ -6,6 +6,7 @@
 #define __LINUX_RESTART_BLOCK_H
 
 #include <linux/compiler.h>
+#include <linux/time64.h>
 #include <linux/types.h>
 
 struct __kernel_timespec;
@@ -50,8 +51,7 @@ struct restart_block {
 			struct pollfd __user *ufds;
 			int nfds;
 			int has_timeout;
-			unsigned long tv_sec;
-			unsigned long tv_nsec;
+			struct timespec64 end_time;
 		} poll;
 	};
 };