diff options
Diffstat (limited to 'fs/file_table.c')
| -rw-r--r-- | fs/file_table.c | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/fs/file_table.c b/fs/file_table.c new file mode 100644 index 0000000..03d83cb --- /dev/null +++ b/fs/file_table.c @@ -0,0 +1,255 @@ +/* + * 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/init.h> +#include <linux/module.h> +#include <linux/smp_lock.h> +#include <linux/fs.h> +#include <linux/security.h> +#include <linux/eventpoll.h> +#include <linux/mount.h> +#include <linux/cdev.h> + +/* sysctl tunables... */ +struct files_stat_struct files_stat = { + .max_files = NR_FILE +}; + +EXPORT_SYMBOL(files_stat); /* Needed by unix.o */ + +/* public. Not pretty! */ + __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock); + +static DEFINE_SPINLOCK(filp_count_lock); + +/* slab constructors and destructors are called from arbitrary + * context and must be fully threaded - use a local spinlock + * to protect files_stat.nr_files + */ +void filp_ctor(void * objp, struct kmem_cache_s *cachep, unsigned long cflags) +{ + if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == + SLAB_CTOR_CONSTRUCTOR) { + unsigned long flags; + spin_lock_irqsave(&filp_count_lock, flags); + files_stat.nr_files++; + spin_unlock_irqrestore(&filp_count_lock, flags); + } +} + +void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags) +{ + unsigned long flags; + spin_lock_irqsave(&filp_count_lock, flags); + files_stat.nr_files--; + spin_unlock_irqrestore(&filp_count_lock, flags); +} + +static inline void file_free(struct file *f) +{ + kmem_cache_free(filp_cachep, f); +} + +/* 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. + */ +struct file *get_empty_filp(void) +{ +static int old_max; + struct file * f; + + /* + * Privileged users can go above max_files + */ + if (files_stat.nr_files < files_stat.max_files || + capable(CAP_SYS_ADMIN)) { + f = kmem_cache_alloc(filp_cachep, GFP_KERNEL); + if (f) { + memset(f, 0, sizeof(*f)); + if (security_file_alloc(f)) { + file_free(f); + goto fail; + } + eventpoll_init_file(f); + atomic_set(&f->f_count, 1); + f->f_uid = current->fsuid; + f->f_gid = current->fsgid; + rwlock_init(&f->f_owner.lock); + /* f->f_version: 0 */ + INIT_LIST_HEAD(&f->f_list); + f->f_maxcount = INT_MAX; + return f; + } + } + + /* Ran out of filps - report that */ + if (files_stat.max_files >= old_max) { + printk(KERN_INFO "VFS: file-max limit %d reached\n", + files_stat.max_files); + old_max = files_stat.max_files; + } else { + /* Big problems... */ + printk(KERN_WARNING "VFS: filp allocation failed\n"); + } +fail: + return NULL; +} + +EXPORT_SYMBOL(get_empty_filp); + +void fastcall fput(struct file *file) +{ + if (atomic_dec_and_test(&file->f_count)) + __fput(file); +} + +EXPORT_SYMBOL(fput); + +/* __fput is called from task context when aio completion releases the last + * last use of a struct file *. Do not use otherwise. + */ +void fastcall __fput(struct file *file) +{ + struct dentry *dentry = file->f_dentry; + struct vfsmount *mnt = file->f_vfsmnt; + struct inode *inode = dentry->d_inode; + + might_sleep(); + /* + * The function eventpoll_release() should be the first called + * in the file cleanup chain. + */ + eventpoll_release(file); + locks_remove_flock(file); + + if (file->f_op && file->f_op->release) + file->f_op->release(inode, file); + security_file_free(file); + if (unlikely(inode->i_cdev != NULL)) + cdev_put(inode->i_cdev); + fops_put(file->f_op); + if (file->f_mode & FMODE_WRITE) + put_write_access(inode); + file_kill(file); + file->f_dentry = NULL; + file->f_vfsmnt = NULL; + file_free(file); + dput(dentry); + mntput(mnt); +} + +struct file fastcall *fget(unsigned int fd) +{ + struct file *file; + struct files_struct *files = current->files; + + spin_lock(&files->file_lock); + file = fcheck_files(files, fd); + if (file) + get_file(file); + spin_unlock(&files->file_lock); + return file; +} + +EXPORT_SYMBOL(fget); + +/* + * Lightweight file lookup - no refcnt increment if fd table isn't shared. + * You can use this only if it is guranteed that the current task already + * holds a refcnt to that file. That check has to be done at fget() only + * and a flag is returned to be passed to the corresponding fput_light(). + * There must not be a cloning between an fget_light/fput_light pair. + */ +struct file fastcall *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 { + spin_lock(&files->file_lock); + file = fcheck_files(files, fd); + if (file) { + get_file(file); + *fput_needed = 1; + } + spin_unlock(&files->file_lock); + } + return file; +} + + +void put_filp(struct file *file) +{ + if (atomic_dec_and_test(&file->f_count)) { + security_file_free(file); + file_kill(file); + file_free(file); + } +} + +void file_move(struct file *file, struct list_head *list) +{ + if (!list) + return; + file_list_lock(); + list_move(&file->f_list, list); + file_list_unlock(); +} + +void file_kill(struct file *file) +{ + if (!list_empty(&file->f_list)) { + file_list_lock(); + list_del_init(&file->f_list); + file_list_unlock(); + } +} + +int fs_may_remount_ro(struct super_block *sb) +{ + struct list_head *p; + + /* Check that no files are currently opened for writing. */ + file_list_lock(); + list_for_each(p, &sb->s_files) { + struct file *file = list_entry(p, struct file, f_list); + struct inode *inode = file->f_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; + } + file_list_unlock(); + return 1; /* Tis' cool bro. */ +too_bad: + file_list_unlock(); + return 0; +} + +void __init files_init(unsigned long mempages) +{ + int n; + /* 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; +} |
