/* * linux/fs/file.c * * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes * * Manage the dynamic fd arrays in the process files_struct. */ #include #include #include #include #include #include #include #include #include #include #include struct fdtable_defer { spinlock_t lock; struct work_struct wq; struct fdtable *next; }; /* * We use this list to defer free fdtables that have vmalloced * sets/arrays. By keeping a per-cpu list, we avoid having to embed * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in * this per-task structure. */ static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list); static inline void * alloc_fdmem(unsigned int size) { if (size <= PAGE_SIZE) return kmalloc(size, GFP_KERNEL); else return vmalloc(size); } static inline void free_fdarr(struct fdtable *fdt) { if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) kfree(fdt->fd); else vfree(fdt->fd); } static inline void free_fdset(struct fdtable *fdt) { if (fdt->max_fds <= (PAGE_SIZE * BITS_PER_BYTE / 2)) kfree(fdt->open_fds); else vfree(fdt->open_fds); } static void free_fdtable_work(struct work_struct *work) { struct fdtable_defer *f = container_of(work, struct fdtable_defer, wq); struct fdtable *fdt; spin_lock_bh(&f->lock); fdt = f->next; f->next = NULL; spin_unlock_bh(&f->lock); while(fdt) { struct fdtable *next = fdt->next; vfree(fdt->fd); free_fdset(fdt); kfree(fdt); fdt = next; } } void free_fdtable_rcu(struct rcu_head *rcu) { struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); struct fdtable_defer *fddef; BUG_ON(!fdt); if (fdt->max_fds <= NR_OPEN_DEFAULT) { /* * This fdtable is embedded in the files structure and that * structure itself is getting destroyed. */ kmem_cache_free(files_cachep, container_of(fdt, struct files_struct, fdtab)); return; } if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) { kfree(fdt->fd); kfree(fdt->open_fds); kfree(fdt); } else { fddef = &get_cpu_var(fdtable_defer_list); spin_lock(&fddef->lock); fdt->next = fddef->next; fddef->next = fdt; /* vmallocs are handled from the workqueue context */ schedule_work(&fddef->wq); spin_unlock(&fddef->lock); put_cpu_var(fdtable_defer_list); } } /* * Expand the fdset in the files_struct. Called with the files spinlock * held for write. */ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) { unsigned int cpy, set; BUG_ON(nfdt->max_fds < ofdt->max_fds); if (ofdt->max_fds == 0) return; cpy = ofdt->max_fds * sizeof(struct file *); set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); memcpy(nfdt->fd, ofdt->fd, cpy); memset((char *)(nfdt->fd) + cpy, 0, set); cpy = ofdt->max_fds / BITS_PER_BYTE; set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; memcpy(nfdt->open_fds, ofdt->open_fds, cpy); memset((char *)(nfdt->open_fds) + cpy, 0, set); memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); memset((char *)(nfdt->close_on_exec) + cpy, 0, set); } static struct fdtable * alloc_fdtable(unsigned int nr) { struct fdtable *fdt; char *data; /* * Figure out how many fds we actually want to support in this fdtable. * Allocation steps are keyed to the size of the fdarray, since it * grows far faster than any of the other dynamic data. We try to fit * the fdarray into comfortable page-tuned chunks: starting at 1024B * and growing in powers of two from there on. */ nr /= (1024 / sizeof(struct file *)); nr = roundup_pow_of_two(nr + 1); nr *= (1024 / sizeof(struct file *)); if (nr > NR_OPEN) nr = NR_OPEN; fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); if (!fdt) goto out; fdt->max_fds = nr; data = alloc_fdmem(nr * sizeof(struct file *)); if (!data) goto out_fdt; fdt->fd = (struct file **)data; data = alloc_fdmem(max_t(unsigned int, 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); if (!data) goto out_arr; fdt->open_fds = (fd_set *)data; data += nr / BITS_PER_BYTE; fdt->close_on_exec = (fd_set *)data; INIT_RCU_HEAD(&fdt->rcu); fdt->next = NULL; return fdt; out_arr: free_fdarr(fdt); out_fdt: kfree(fdt); out: return NULL; } /* * Expand the file descriptor table. * This function will allocate a new fdtable and both fd array and fdset, of * the given size. * Return <0 error code on error; 1 on successful completion. * The files->file_lock should be held on entry, and will be held on exit. */ static int expand_fdtable(struct files_struct *files, int nr) __releases(files->file_lock) __acquires(files->file_lock) { struct fdtable *new_fdt, *cur_fdt; spin_unlock(&files->file_lock); new_fdt = alloc_fdtable(nr); spin_lock(&files->file_lock); if (!new_fdt) return -ENOMEM; /* * Check again since another task may have expanded the fd table while * we dropped the lock */ cur_fdt = files_fdtable(files); if (nr >= cur_fdt->max_fds) { /* Continue as planned */ copy_fdtable(new_fdt, cur_fdt); rcu_assign_pointer(files->fdt, new_fdt); if (cur_fdt->max_fds > NR_OPEN_DEFAULT) free_fdtable(cur_fdt); } else { /* Somebody else expanded, so undo our attempt */ free_fdarr(new_fdt); free_fdset(new_fdt); kfree(new_fdt); } return 1; } /* * Expand files. * This function will expand the file structures, if the requested size exceeds * the current capacity and there is room for expansion. * Return <0 error code on error; 0 when nothing done; 1 when files were * expanded and execution may have blocked. * The files->file_lock should be held on entry, and will be held on exit. */ int expand_files(struct files_struct *files, int nr) { struct fdtable *fdt; fdt = files_fdtable(files); /* Do we need to expand? */ if (nr < fdt->max_fds) return 0; /* Can we expand? */ if (nr >= NR_OPEN) return -EMFILE; /* All good, so we try */ return expand_fdtable(files, nr); } static void __devinit fdtable_defer_list_init(int cpu) { struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu); spin_lock_init(&fddef->lock); INIT_WORK(&fddef->wq, free_fdtable_work); fddef->next = NULL; } void __init files_defer_init(void) { int i; for_each_possible_cpu(i) fdtable_defer_list_init(i); }