/* * Copyright (c) 2009-2019 The DragonFly Project. All rights reserved. * * This code is derived from software contributed to The DragonFly Project * by Alex Hornung <ahornung@gmail.com> * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name of The DragonFly Project nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific, prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/param.h> #include <sys/systm.h> #include <sys/kernel.h> #include <sys/malloc.h> #include <machine/limits.h> #include <sys/devfs.h> MALLOC_DECLARE(M_DEVFS); /* * Locallized lock to ensure the integrity of the bitmap/cloning * code. Callers using chk/set sequences must still check for races * or have their own locks. * * We use a recursive lock only to allow *_get() to call *_set(). */ static struct lock devfs_bitmap_lock = LOCK_INITIALIZER("dbmap", 0, LK_CANRECURSE); /* * DEVFS clone bitmap functions */ void devfs_clone_bitmap_init(struct devfs_bitmap *bitmap) { bitmap->chunks = DEVFS_BITMAP_INITIAL_SIZE; bitmap->bitmap = kmalloc(bitmap->chunks * sizeof(u_long), M_DEVFS, M_WAITOK); memset(bitmap->bitmap, -1, bitmap->chunks * sizeof(u_long)); } void devfs_clone_bitmap_uninit(struct devfs_bitmap *bitmap) { kfree(bitmap->bitmap, M_DEVFS); } /* * Extend the bitmap past (not just up to) 'newchunks' chunks. While * probably not necessary, we go a little further and give ourselves * one extra chunk's worth of bitmap beyond what is required. */ static void devfs_clone_bitmap_extend(struct devfs_bitmap *bitmap, int newchunks) { int oldchunks = bitmap->chunks; bitmap->chunks = newchunks + 2; bitmap->bitmap = krealloc(bitmap->bitmap, sizeof(u_long) * bitmap->chunks, M_DEVFS, M_WAITOK); memset(bitmap->bitmap + oldchunks, -1, sizeof(u_long) * (bitmap->chunks - oldchunks)); } /* * This helper function determines the next available free unit in the * bitmap, extending the bitmap if necessary. It cannot fail. */ static int devfs_clone_bitmap_fff(struct devfs_bitmap *bitmap) { u_long curbitmap; int bit, i; int chunks; chunks = bitmap->chunks; for (i = 0; i < chunks + 1; i++) { if (i == chunks) devfs_clone_bitmap_extend(bitmap, i); curbitmap = bitmap->bitmap[i]; if (curbitmap) { curbitmap &= (~curbitmap)+1; for (bit = 1; curbitmap != 1; bit++) curbitmap >>= 1; return (bit - 1 + (i << 3) * sizeof(curbitmap)); } } /* * NOT REACHED */ panic("devfs_clone_bitmap_fff"); return -1; } /* * Caller wants to know if the specified unit has been allocated * or not. Return 0, indicating that it has not been allocated. * * Caller must hold a lock to prevent chk-to-set races. Devfs also * obtains a temporary lock, juse in case, to ensure structural * integrity. * * (the bitmap implements 0=allocated, 1=not-allocated but the * return value is inverted). */ int devfs_clone_bitmap_chk(struct devfs_bitmap *bitmap, int unit) { int chunk; int res; chunk = unit / (sizeof(u_long) * 8); unit -= chunk * (sizeof(u_long) * 8); lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); if (chunk >= bitmap->chunks) { lockmgr(&devfs_bitmap_lock, LK_RELEASE); return 0; /* device does not exist */ } res = !((bitmap->bitmap[chunk]) & (1UL << unit)); lockmgr(&devfs_bitmap_lock, LK_RELEASE); return res; } /* * Unconditionally mark the specified unit as allocated in the bitmap. * * Caller must hold a lock to prevent chk-to-set races, or otherwise * check for a return value < 0 from this routine. If the unit had * never been allocated in the past, a token lock might not be sufficient * to avoid races (if this function must extend the bitmap it could block * temporary in kmalloc()). * * devfs acquires a temporary lock to ensure structural integrity. * * If the bit is already clear (indicating that the unit is already * allocated), return -1. Otherwise return 0. */ int devfs_clone_bitmap_set(struct devfs_bitmap *bitmap, int unit) { int chunk; int res; chunk = unit / (sizeof(u_long) * 8); unit -= chunk * (sizeof(u_long) * 8); lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); if (chunk >= bitmap->chunks) devfs_clone_bitmap_extend(bitmap, chunk); if (bitmap->bitmap[chunk] & (1UL << unit)) { bitmap->bitmap[chunk] &= ~(1UL << unit); res = 0; } else { res = -1; } lockmgr(&devfs_bitmap_lock, LK_RELEASE); return res; } /* * Unconditionally deallocate a unit number. Caller must synchronize any * destroy_dev()'s the device called before clearing the bitmap bit to * avoid races against a new clone. */ void devfs_clone_bitmap_put(struct devfs_bitmap *bitmap, int unit) { int chunk; devfs_config(); chunk = unit / (sizeof(u_long) * 8); unit -= chunk * (sizeof(u_long) * 8); lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); if (chunk < bitmap->chunks) bitmap->bitmap[chunk] |= (1UL << unit); lockmgr(&devfs_bitmap_lock, LK_RELEASE); } /* * Conditionally allocate a unit from the bitmap. Returns -1 if no * more units are available. * * Caller must hold a lock to avoid bitmap races. Since *_fff() below * pre-extends the bitmap as necessary, a token lock is sufficient. */ int devfs_clone_bitmap_get(struct devfs_bitmap *bitmap, int limit) { int unit; lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); unit = devfs_clone_bitmap_fff(bitmap); if (limit > 0 && unit > limit) { unit = -1; } else { devfs_clone_bitmap_set(bitmap, unit); } lockmgr(&devfs_bitmap_lock, LK_RELEASE); return unit; }
