1fd36adcd9
Replace the fd_sets in struct fdtable with an array of unsigned longs and then
use the standard non-atomic bit operations rather than the FD_* macros.
This:
(1) Removes the abuses of struct fd_set:
(a) Since we don't want to allocate a full fd_set the vast majority of the
time, we actually, in effect, just allocate a just-big-enough array of
unsigned longs and cast it to an fd_set type - so why bother with the
fd_set at all?
(b) Some places outside of the core fdtable handling code (such as
SELinux) want to look inside the array of unsigned longs hidden inside
the fd_set struct for more efficient iteration over the entire set.
(2) Eliminates the use of FD_*() macros in the kernel completely.
(3) Permits the __FD_*() macros to be deleted entirely where not exposed to
userspace.
Signed-off-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/20120216174954.23314.48147.stgit@warthog.procyon.org.uk
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
130 lines
3 KiB
C
130 lines
3 KiB
C
/*
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* descriptor table internals; you almost certainly want file.h instead.
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*/
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#ifndef __LINUX_FDTABLE_H
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#define __LINUX_FDTABLE_H
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#include <linux/posix_types.h>
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#include <linux/compiler.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/types.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/atomic.h>
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/*
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* The default fd array needs to be at least BITS_PER_LONG,
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* as this is the granularity returned by copy_fdset().
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*/
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#define NR_OPEN_DEFAULT BITS_PER_LONG
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struct fdtable {
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unsigned int max_fds;
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struct file __rcu **fd; /* current fd array */
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unsigned long *close_on_exec;
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unsigned long *open_fds;
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struct rcu_head rcu;
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struct fdtable *next;
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};
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static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
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{
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__set_bit(fd, fdt->close_on_exec);
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}
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static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
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{
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__clear_bit(fd, fdt->close_on_exec);
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}
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static inline bool close_on_exec(int fd, const struct fdtable *fdt)
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{
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return test_bit(fd, fdt->close_on_exec);
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}
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static inline void __set_open_fd(int fd, struct fdtable *fdt)
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{
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__set_bit(fd, fdt->open_fds);
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}
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static inline void __clear_open_fd(int fd, struct fdtable *fdt)
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{
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__clear_bit(fd, fdt->open_fds);
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}
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static inline bool fd_is_open(int fd, const struct fdtable *fdt)
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{
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return test_bit(fd, fdt->open_fds);
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}
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/*
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* Open file table structure
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*/
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struct files_struct {
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/*
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* read mostly part
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*/
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atomic_t count;
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struct fdtable __rcu *fdt;
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struct fdtable fdtab;
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/*
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* written part on a separate cache line in SMP
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*/
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spinlock_t file_lock ____cacheline_aligned_in_smp;
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int next_fd;
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unsigned long close_on_exec_init[1];
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unsigned long open_fds_init[1];
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struct file __rcu * fd_array[NR_OPEN_DEFAULT];
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};
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#define rcu_dereference_check_fdtable(files, fdtfd) \
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(rcu_dereference_check((fdtfd), \
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lockdep_is_held(&(files)->file_lock) || \
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atomic_read(&(files)->count) == 1 || \
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rcu_my_thread_group_empty()))
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#define files_fdtable(files) \
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(rcu_dereference_check_fdtable((files), (files)->fdt))
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struct file_operations;
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struct vfsmount;
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struct dentry;
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extern int expand_files(struct files_struct *, int nr);
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extern void free_fdtable_rcu(struct rcu_head *rcu);
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extern void __init files_defer_init(void);
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static inline void free_fdtable(struct fdtable *fdt)
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{
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call_rcu(&fdt->rcu, free_fdtable_rcu);
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}
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static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
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{
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struct file * file = NULL;
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struct fdtable *fdt = files_fdtable(files);
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if (fd < fdt->max_fds)
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file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
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return file;
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}
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/*
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* Check whether the specified fd has an open file.
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*/
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#define fcheck(fd) fcheck_files(current->files, fd)
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struct task_struct;
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struct files_struct *get_files_struct(struct task_struct *);
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void put_files_struct(struct files_struct *fs);
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void reset_files_struct(struct files_struct *);
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int unshare_files(struct files_struct **);
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struct files_struct *dup_fd(struct files_struct *, int *);
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extern struct kmem_cache *files_cachep;
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#endif /* __LINUX_FDTABLE_H */
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