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-rw-r--r--fs/file_table.c507
1 files changed, 507 insertions, 0 deletions
diff --git a/fs/file_table.c b/fs/file_table.c
new file mode 100644
index 00000000..a04bdd81
--- /dev/null
+++ b/fs/file_table.c
@@ -0,0 +1,507 @@
+/*
+ * linux/fs/file_table.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
+ */
+
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/security.h>
+#include <linux/eventpoll.h>
+#include <linux/rcupdate.h>
+#include <linux/mount.h>
+#include <linux/capability.h>
+#include <linux/cdev.h>
+#include <linux/fsnotify.h>
+#include <linux/sysctl.h>
+#include <linux/lglock.h>
+#include <linux/percpu_counter.h>
+#include <linux/percpu.h>
+#include <linux/ima.h>
+
+#include <asm/atomic.h>
+
+#include "internal.h"
+
+/* sysctl tunables... */
+struct files_stat_struct files_stat = {
+ .max_files = NR_FILE
+};
+
+DECLARE_LGLOCK(files_lglock);
+DEFINE_LGLOCK(files_lglock);
+
+/* SLAB cache for file structures */
+static struct kmem_cache *filp_cachep __read_mostly;
+
+static struct percpu_counter nr_files __cacheline_aligned_in_smp;
+
+static inline void file_free_rcu(struct rcu_head *head)
+{
+ struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
+
+ put_cred(f->f_cred);
+ kmem_cache_free(filp_cachep, f);
+}
+
+static inline void file_free(struct file *f)
+{
+ percpu_counter_dec(&nr_files);
+ file_check_state(f);
+ call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
+}
+
+/*
+ * Return the total number of open files in the system
+ */
+static int get_nr_files(void)
+{
+ return percpu_counter_read_positive(&nr_files);
+}
+
+/*
+ * Return the maximum number of open files in the system
+ */
+int get_max_files(void)
+{
+ return files_stat.max_files;
+}
+EXPORT_SYMBOL_GPL(get_max_files);
+
+/*
+ * Handle nr_files sysctl
+ */
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+int proc_nr_files(ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ files_stat.nr_files = get_nr_files();
+ return proc_dointvec(table, write, buffer, lenp, ppos);
+}
+#else
+int proc_nr_files(ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return -ENOSYS;
+}
+#endif
+
+/* Find an unused file structure and return a pointer to it.
+ * Returns NULL, if there are no more free file structures or
+ * we run out of memory.
+ *
+ * Be very careful using this. You are responsible for
+ * getting write access to any mount that you might assign
+ * to this filp, if it is opened for write. If this is not
+ * done, you will imbalance int the mount's writer count
+ * and a warning at __fput() time.
+ */
+struct file *get_empty_filp(void)
+{
+ const struct cred *cred = current_cred();
+ static int old_max;
+ struct file * f;
+
+ /*
+ * Privileged users can go above max_files
+ */
+ if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
+ /*
+ * percpu_counters are inaccurate. Do an expensive check before
+ * we go and fail.
+ */
+ if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
+ goto over;
+ }
+
+ f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
+ if (f == NULL)
+ goto fail;
+
+ percpu_counter_inc(&nr_files);
+ if (security_file_alloc(f))
+ goto fail_sec;
+
+ INIT_LIST_HEAD(&f->f_u.fu_list);
+ atomic_long_set(&f->f_count, 1);
+ rwlock_init(&f->f_owner.lock);
+ f->f_cred = get_cred(cred);
+ spin_lock_init(&f->f_lock);
+ eventpoll_init_file(f);
+ /* f->f_version: 0 */
+ return f;
+
+over:
+ /* Ran out of filps - report that */
+ if (get_nr_files() > old_max) {
+ printk(KERN_INFO "VFS: file-max limit %d reached\n",
+ get_max_files());
+ old_max = get_nr_files();
+ }
+ goto fail;
+
+fail_sec:
+ file_free(f);
+fail:
+ return NULL;
+}
+
+/**
+ * alloc_file - allocate and initialize a 'struct file'
+ * @mnt: the vfsmount on which the file will reside
+ * @dentry: the dentry representing the new file
+ * @mode: the mode with which the new file will be opened
+ * @fop: the 'struct file_operations' for the new file
+ *
+ * Use this instead of get_empty_filp() to get a new
+ * 'struct file'. Do so because of the same initialization
+ * pitfalls reasons listed for init_file(). This is a
+ * preferred interface to using init_file().
+ *
+ * If all the callers of init_file() are eliminated, its
+ * code should be moved into this function.
+ */
+struct file *alloc_file(struct path *path, fmode_t mode,
+ const struct file_operations *fop)
+{
+ struct file *file;
+
+ file = get_empty_filp();
+ if (!file)
+ return NULL;
+
+ file->f_path = *path;
+ file->f_mapping = path->dentry->d_inode->i_mapping;
+ file->f_mode = mode;
+ file->f_op = fop;
+
+ /*
+ * These mounts don't really matter in practice
+ * for r/o bind mounts. They aren't userspace-
+ * visible. We do this for consistency, and so
+ * that we can do debugging checks at __fput()
+ */
+ if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
+ file_take_write(file);
+ WARN_ON(mnt_clone_write(path->mnt));
+ }
+ ima_counts_get(file);
+ return file;
+}
+EXPORT_SYMBOL(alloc_file);
+
+/**
+ * drop_file_write_access - give up ability to write to a file
+ * @file: the file to which we will stop writing
+ *
+ * This is a central place which will give up the ability
+ * to write to @file, along with access to write through
+ * its vfsmount.
+ */
+void drop_file_write_access(struct file *file)
+{
+ struct vfsmount *mnt = file->f_path.mnt;
+ struct dentry *dentry = file->f_path.dentry;
+ struct inode *inode = dentry->d_inode;
+
+ put_write_access(inode);
+
+ if (special_file(inode->i_mode))
+ return;
+ if (file_check_writeable(file) != 0)
+ return;
+ mnt_drop_write(mnt);
+ file_release_write(file);
+}
+EXPORT_SYMBOL_GPL(drop_file_write_access);
+
+/* the real guts of fput() - releasing the last reference to file
+ */
+static void __fput(struct file *file)
+{
+ struct dentry *dentry = file->f_path.dentry;
+ struct vfsmount *mnt = file->f_path.mnt;
+ struct inode *inode = dentry->d_inode;
+
+ might_sleep();
+
+ fsnotify_close(file);
+ /*
+ * The function eventpoll_release() should be the first called
+ * in the file cleanup chain.
+ */
+ eventpoll_release(file);
+ locks_remove_flock(file);
+
+ if (unlikely(file->f_flags & FASYNC)) {
+ if (file->f_op && file->f_op->fasync)
+ file->f_op->fasync(-1, file, 0);
+ }
+ if (file->f_op && file->f_op->release)
+ file->f_op->release(inode, file);
+ security_file_free(file);
+ ima_file_free(file);
+ if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
+ cdev_put(inode->i_cdev);
+ fops_put(file->f_op);
+ put_pid(file->f_owner.pid);
+ file_sb_list_del(file);
+ if (file->f_mode & FMODE_WRITE)
+ drop_file_write_access(file);
+ file->f_path.dentry = NULL;
+ file->f_path.mnt = NULL;
+ file_free(file);
+ dput(dentry);
+ mntput(mnt);
+}
+
+void fput(struct file *file)
+{
+ if (atomic_long_dec_and_test(&file->f_count))
+ __fput(file);
+}
+
+EXPORT_SYMBOL(fput);
+
+struct file *fget(unsigned int fd)
+{
+ struct file *file;
+ struct files_struct *files = current->files;
+
+ rcu_read_lock();
+ file = fcheck_files(files, fd);
+ if (file) {
+ if (!atomic_long_inc_not_zero(&file->f_count)) {
+ /* File object ref couldn't be taken */
+ rcu_read_unlock();
+ return NULL;
+ }
+ }
+ rcu_read_unlock();
+
+ return file;
+}
+
+EXPORT_SYMBOL(fget);
+
+/*
+ * Lightweight file lookup - no refcnt increment if fd table isn't shared.
+ *
+ * You can use this instead of fget if you satisfy all of the following
+ * conditions:
+ * 1) You must call fput_light before exiting the syscall and returning control
+ * to userspace (i.e. you cannot remember the returned struct file * after
+ * returning to userspace).
+ * 2) You must not call filp_close on the returned struct file * in between
+ * calls to fget_light and fput_light.
+ * 3) You must not clone the current task in between the calls to fget_light
+ * and fput_light.
+ *
+ * The fput_needed flag returned by fget_light should be passed to the
+ * corresponding fput_light.
+ */
+struct file *fget_light(unsigned int fd, int *fput_needed)
+{
+ struct file *file;
+ struct files_struct *files = current->files;
+
+ *fput_needed = 0;
+ if (likely((atomic_read(&files->count) == 1))) {
+ file = fcheck_files(files, fd);
+ } else {
+ rcu_read_lock();
+ file = fcheck_files(files, fd);
+ if (file) {
+ if (atomic_long_inc_not_zero(&file->f_count))
+ *fput_needed = 1;
+ else
+ /* Didn't get the reference, someone's freed */
+ file = NULL;
+ }
+ rcu_read_unlock();
+ }
+
+ return file;
+}
+
+void put_filp(struct file *file)
+{
+ if (atomic_long_dec_and_test(&file->f_count)) {
+ security_file_free(file);
+ file_sb_list_del(file);
+ file_free(file);
+ }
+}
+
+static inline int file_list_cpu(struct file *file)
+{
+#ifdef CONFIG_SMP
+ return file->f_sb_list_cpu;
+#else
+ return smp_processor_id();
+#endif
+}
+
+/* helper for file_sb_list_add to reduce ifdefs */
+static inline void __file_sb_list_add(struct file *file, struct super_block *sb)
+{
+ struct list_head *list;
+#ifdef CONFIG_SMP
+ int cpu;
+ cpu = smp_processor_id();
+ file->f_sb_list_cpu = cpu;
+ list = per_cpu_ptr(sb->s_files, cpu);
+#else
+ list = &sb->s_files;
+#endif
+ list_add(&file->f_u.fu_list, list);
+}
+
+/**
+ * file_sb_list_add - add a file to the sb's file list
+ * @file: file to add
+ * @sb: sb to add it to
+ *
+ * Use this function to associate a file with the superblock of the inode it
+ * refers to.
+ */
+void file_sb_list_add(struct file *file, struct super_block *sb)
+{
+ lg_local_lock(files_lglock);
+ __file_sb_list_add(file, sb);
+ lg_local_unlock(files_lglock);
+}
+
+/**
+ * file_sb_list_del - remove a file from the sb's file list
+ * @file: file to remove
+ * @sb: sb to remove it from
+ *
+ * Use this function to remove a file from its superblock.
+ */
+void file_sb_list_del(struct file *file)
+{
+ if (!list_empty(&file->f_u.fu_list)) {
+ lg_local_lock_cpu(files_lglock, file_list_cpu(file));
+ list_del_init(&file->f_u.fu_list);
+ lg_local_unlock_cpu(files_lglock, file_list_cpu(file));
+ }
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * These macros iterate all files on all CPUs for a given superblock.
+ * files_lglock must be held globally.
+ */
+#define do_file_list_for_each_entry(__sb, __file) \
+{ \
+ int i; \
+ for_each_possible_cpu(i) { \
+ struct list_head *list; \
+ list = per_cpu_ptr((__sb)->s_files, i); \
+ list_for_each_entry((__file), list, f_u.fu_list)
+
+#define while_file_list_for_each_entry \
+ } \
+}
+
+#else
+
+#define do_file_list_for_each_entry(__sb, __file) \
+{ \
+ struct list_head *list; \
+ list = &(sb)->s_files; \
+ list_for_each_entry((__file), list, f_u.fu_list)
+
+#define while_file_list_for_each_entry \
+}
+
+#endif
+
+int fs_may_remount_ro(struct super_block *sb)
+{
+ struct file *file;
+ /* Check that no files are currently opened for writing. */
+ lg_global_lock(files_lglock);
+ do_file_list_for_each_entry(sb, file) {
+ struct inode *inode = file->f_path.dentry->d_inode;
+
+ /* File with pending delete? */
+ if (inode->i_nlink == 0)
+ goto too_bad;
+
+ /* Writeable file? */
+ if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
+ goto too_bad;
+ } while_file_list_for_each_entry;
+ lg_global_unlock(files_lglock);
+ return 1; /* Tis' cool bro. */
+too_bad:
+ lg_global_unlock(files_lglock);
+ return 0;
+}
+
+/**
+ * mark_files_ro - mark all files read-only
+ * @sb: superblock in question
+ *
+ * All files are marked read-only. We don't care about pending
+ * delete files so this should be used in 'force' mode only.
+ */
+void mark_files_ro(struct super_block *sb)
+{
+ struct file *f;
+
+retry:
+ lg_global_lock(files_lglock);
+ do_file_list_for_each_entry(sb, f) {
+ struct vfsmount *mnt;
+ if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
+ continue;
+ if (!file_count(f))
+ continue;
+ if (!(f->f_mode & FMODE_WRITE))
+ continue;
+ spin_lock(&f->f_lock);
+ f->f_mode &= ~FMODE_WRITE;
+ spin_unlock(&f->f_lock);
+ if (file_check_writeable(f) != 0)
+ continue;
+ file_release_write(f);
+ mnt = mntget(f->f_path.mnt);
+ /* This can sleep, so we can't hold the spinlock. */
+ lg_global_unlock(files_lglock);
+ mnt_drop_write(mnt);
+ mntput(mnt);
+ goto retry;
+ } while_file_list_for_each_entry;
+ lg_global_unlock(files_lglock);
+}
+
+void __init files_init(unsigned long mempages)
+{
+ int n;
+
+ filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
+ SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+
+ /*
+ * One file with associated inode and dcache is very roughly 1K.
+ * Per default don't use more than 10% of our memory for files.
+ */
+
+ n = (mempages * (PAGE_SIZE / 1024)) / 10;
+ files_stat.max_files = n;
+ if (files_stat.max_files < NR_FILE)
+ files_stat.max_files = NR_FILE;
+ files_defer_init();
+ lg_lock_init(files_lglock);
+ percpu_counter_init(&nr_files, 0);
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-24 14:32:30 +0000