/* * linux/fs/file.c * * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes * * Manage the dynamic fd arrays in the process files_struct. */ #include <linux/fs.h> #include <linux/mm.h> #include <linux/time.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/file.h> #include <linux/bitops.h> #include <linux/interrupt.h> #include <linux/spinlock.h> #include <linux/rcupdate.h> #include <linux/workqueue.h> struct fdtable_defer { spinlock_t lock; struct work_struct wq; struct timer_list timer; 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); /* * Allocate an fd array, using kmalloc or vmalloc. * Note: the array isn't cleared at allocation time. */ struct file ** alloc_fd_array(int num) { struct file **new_fds; int size = num * sizeof(struct file *); if (size <= PAGE_SIZE) new_fds = (struct file **) kmalloc(size, GFP_KERNEL); else new_fds = (struct file **) vmalloc(size); return new_fds; } void free_fd_array(struct file **array, int num) { int size = num * sizeof(struct file *); if (!array) { printk (KERN_ERR "free_fd_array: array = 0 (num = %d)\n", num); return; } if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */ return; else if (size <= PAGE_SIZE) kfree(array); else vfree(array); } static void __free_fdtable(struct fdtable *fdt) { free_fdset(fdt->open_fds, fdt->max_fdset); free_fdset(fdt->close_on_exec, fdt->max_fdset); free_fd_array(fdt->fd, fdt->max_fds); kfree(fdt); } static void fdtable_timer(unsigned long data) { struct fdtable_defer *fddef = (struct fdtable_defer *)data; spin_lock(&fddef->lock); /* * If someone already emptied the queue return. */ if (!fddef->next) goto out; if (!schedule_work(&fddef->wq)) mod_timer(&fddef->timer, 5); out: spin_unlock(&fddef->lock); } static void free_fdtable_work(struct fdtable_defer *f) { 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; __free_fdtable(fdt); fdt = next; } } static void free_fdtable_rcu(struct rcu_head *rcu) { struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); int fdset_size, fdarray_size; struct fdtable_defer *fddef; BUG_ON(!fdt); fdset_size = fdt->max_fdset / 8; fdarray_size = fdt->max_fds * sizeof(struct file *); if (fdt->free_files) { /* * The this fdtable was embedded in the files structure * and the files structure itself was getting destroyed. * It is now safe to free the files structure. */ kmem_cache_free(files_cachep, fdt->free_files); return; } if (fdt->max_fdset <= EMBEDDED_FD_SET_SIZE && fdt->max_fds <= NR_OPEN_DEFAULT) { /* * The fdtable was embedded */ return; } if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) { kfree(fdt->open_fds); kfree(fdt->close_on_exec); kfree(fdt->fd); 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. * If the per-cpu workqueue is running, then we * defer work scheduling through a timer. */ if (!schedule_work(&fddef->wq)) mod_timer(&fddef->timer, 5); spin_unlock(&fddef->lock); put_cpu_var(fdtable_defer_list); } } void free_fdtable(struct fdtable *fdt) { if (fdt->free_files || fdt->max_fdset > EMBEDDED_FD_SET_SIZE || fdt->max_fds > NR_OPEN_DEFAULT) call_rcu(&fdt->rcu, free_fdtable_rcu); } /* * Expand the fdset in the files_struct. Called with the files spinlock * held for write. */ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *fdt) { int i; int count; BUG_ON(nfdt->max_fdset < fdt->max_fdset); BUG_ON(nfdt->max_fds < fdt->max_fds); /* Copy the existing tables and install the new pointers */ i = fdt->max_fdset / (sizeof(unsigned long) * 8); count = (nfdt->max_fdset - fdt->max_fdset) / 8; /* * Don't copy the entire array if the current fdset is * not yet initialised. */ if (i) { memcpy (nfdt->open_fds, fdt->open_fds, fdt->max_fdset/8); memcpy (nfdt->close_on_exec, fdt->close_on_exec, fdt->max_fdset/8); memset (&nfdt->open_fds->fds_bits[i], 0, count); memset (&nfdt->close_on_exec->fds_bits[i], 0, count); } /* Don't copy/clear the array if we are creating a new fd array for fork() */ if (fdt->max_fds) { memcpy(nfdt->fd, fdt->fd, fdt->max_fds * sizeof(struct file *)); /* clear the remainder of the array */ memset(&nfdt->fd[fdt->max_fds], 0, (nfdt->max_fds - fdt->max_fds) * sizeof(struct file *)); } } /* * Allocate an fdset array, using kmalloc or vmalloc. * Note: the array isn't cleared at allocation time. */ fd_set * alloc_fdset(int num) { fd_set *new_fdset; int size = num / 8; if (size <= PAGE_SIZE) new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL); else new_fdset = (fd_set *) vmalloc(size); return new_fdset; } void free_fdset(fd_set *array, int num) { if (num <= EMBEDDED_FD_SET_SIZE) /* Don't free an embedded fdset */ return; else if (num <= 8 * PAGE_SIZE) kfree(array); else vfree(array); } static struct fdtable *alloc_fdtable(int nr) { struct fdtable *fdt = NULL; int nfds = 0; fd_set *new_openset = NULL, *new_execset = NULL; struct file **new_fds; fdt = kzalloc(sizeof(*fdt), GFP_KERNEL); if (!fdt) goto out; nfds = max_t(int, 8 * L1_CACHE_BYTES, roundup_pow_of_two(nr + 1)); if (nfds > NR_OPEN) nfds = NR_OPEN; new_openset = alloc_fdset(nfds); new_execset = alloc_fdset(nfds); if (!new_openset || !new_execset) goto out; fdt->open_fds = new_openset; fdt->close_on_exec = new_execset; fdt->max_fdset = nfds; nfds = NR_OPEN_DEFAULT; /* * Expand to the max in easy steps, and keep expanding it until * we have enough for the requested fd array size. */ do { #if NR_OPEN_DEFAULT < 256 if (nfds < 256) nfds = 256; else #endif if (nfds < (PAGE_SIZE / sizeof(struct file *))) nfds = PAGE_SIZE / sizeof(struct file *); else { nfds = nfds * 2; if (nfds > NR_OPEN) nfds = NR_OPEN; } } while (nfds <= nr); new_fds = alloc_fd_array(nfds); if (!new_fds) goto out2; fdt->fd = new_fds; fdt->max_fds = nfds; fdt->free_files = NULL; return fdt; out2: nfds = fdt->max_fdset; out: free_fdset(new_openset, nfds); free_fdset(new_execset, nfds); kfree(fdt); 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 || nr >= cur_fdt->max_fdset) { /* Continue as planned */ copy_fdtable(new_fdt, cur_fdt); rcu_assign_pointer(files->fdt, new_fdt); free_fdtable(cur_fdt); } else { /* Somebody else expanded, so undo our attempt */ __free_fdtable(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_fdset && nr < fdt->max_fds) return 0; /* Can we expand? */ if (fdt->max_fdset >= NR_OPEN || fdt->max_fds >= NR_OPEN || 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, (void (*)(void *))free_fdtable_work, fddef); init_timer(&fddef->timer); fddef->timer.data = (unsigned long)fddef; fddef->timer.function = fdtable_timer; fddef->next = NULL; } void __init files_defer_init(void) { int i; for_each_possible_cpu(i) fdtable_defer_list_init(i); }