X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=drivers%2Fblock%2Floop.c;h=6f011d0d8e97a98c0aa661ae6a2223bb73a72fda;hb=f7f1b0f1e2fbadeab12d24236000e778aa9b1ead;hp=3efc2ea7ad64395b71a41da99ca0ab7f3edfea4a;hpb=e3f6fb6212a7102bdb56ba38fa1e98fe72950475;p=linux-2.6.git diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 3efc2ea7a..6f011d0d8 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -39,6 +39,11 @@ * Support up to 256 loop devices * Heinz Mauelshagen , Feb 2002 * + * Support for falling back on the write file operation when the address space + * operations prepare_write and/or commit_write are not available on the + * backing filesystem. + * Anton Altaparmakov, 16 Feb 2005 + * * Still To Fix: * - Advisory locking is ignored here. * - Should use an own CAP_* category instead of CAP_SYS_ADMIN @@ -67,6 +72,8 @@ #include #include /* for invalidate_bdev() */ #include +#include +#include #include @@ -127,7 +134,7 @@ static int transfer_xor(struct loop_device *lo, int cmd, static int xor_init(struct loop_device *lo, const struct loop_info64 *info) { - if (info->lo_encrypt_key_size <= 0) + if (unlikely(info->lo_encrypt_key_size <= 0)) return -EINVAL; return 0; } @@ -173,7 +180,7 @@ figure_loop_size(struct loop_device *lo) loff_t size = get_loop_size(lo, lo->lo_backing_file); sector_t x = (sector_t)size; - if ((loff_t)x != size) + if (unlikely((loff_t)x != size)) return -EFBIG; set_capacity(disks[lo->lo_number], x); @@ -186,23 +193,27 @@ lo_do_transfer(struct loop_device *lo, int cmd, struct page *lpage, unsigned loffs, int size, sector_t rblock) { - if (!lo->transfer) + if (unlikely(!lo->transfer)) return 0; return lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock); } -static int -do_lo_send(struct loop_device *lo, struct bio_vec *bvec, int bsize, loff_t pos) +/** + * do_lo_send_aops - helper for writing data to a loop device + * + * This is the fast version for backing filesystems which implement the address + * space operations prepare_write and commit_write. + */ +static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, + int bsize, loff_t pos, struct page *page) { struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */ struct address_space *mapping = file->f_mapping; struct address_space_operations *aops = mapping->a_ops; - struct page *page; pgoff_t index; - unsigned size, offset, bv_offs; - int len; - int ret = 0; + unsigned offset, bv_offs; + int len, ret = 0; down(&mapping->host->i_sem); index = pos >> PAGE_CACHE_SHIFT; @@ -211,23 +222,22 @@ do_lo_send(struct loop_device *lo, struct bio_vec *bvec, int bsize, loff_t pos) len = bvec->bv_len; while (len > 0) { sector_t IV; + unsigned size; int transfer_result; IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9); - size = PAGE_CACHE_SIZE - offset; if (size > len) size = len; - page = grab_cache_page(mapping, index); - if (!page) + if (unlikely(!page)) goto fail; - if (aops->prepare_write(file, page, offset, offset+size)) + if (unlikely(aops->prepare_write(file, page, offset, + offset + size))) goto unlock; transfer_result = lo_do_transfer(lo, WRITE, page, offset, - bvec->bv_page, bv_offs, - size, IV); - if (transfer_result) { + bvec->bv_page, bv_offs, size, IV); + if (unlikely(transfer_result)) { char *kaddr; /* @@ -241,9 +251,10 @@ do_lo_send(struct loop_device *lo, struct bio_vec *bvec, int bsize, loff_t pos) kunmap_atomic(kaddr, KM_USER0); } flush_dcache_page(page); - if (aops->commit_write(file, page, offset, offset+size)) + if (unlikely(aops->commit_write(file, page, offset, + offset + size))) goto unlock; - if (transfer_result) + if (unlikely(transfer_result)) goto unlock; bv_offs += size; len -= size; @@ -253,32 +264,125 @@ do_lo_send(struct loop_device *lo, struct bio_vec *bvec, int bsize, loff_t pos) unlock_page(page); page_cache_release(page); } - up(&mapping->host->i_sem); out: + up(&mapping->host->i_sem); return ret; - unlock: unlock_page(page); page_cache_release(page); fail: - up(&mapping->host->i_sem); ret = -1; goto out; } -static int -lo_send(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos) +/** + * __do_lo_send_write - helper for writing data to a loop device + * + * This helper just factors out common code between do_lo_send_direct_write() + * and do_lo_send_write(). + */ +static inline int __do_lo_send_write(struct file *file, + u8 __user *buf, const int len, loff_t pos) { + ssize_t bw; + mm_segment_t old_fs = get_fs(); + + set_fs(get_ds()); + bw = file->f_op->write(file, buf, len, &pos); + set_fs(old_fs); + if (likely(bw == len)) + return 0; + printk(KERN_ERR "loop: Write error at byte offset %llu, length %i.\n", + (unsigned long long)pos, len); + if (bw >= 0) + bw = -EIO; + return bw; +} + +/** + * do_lo_send_direct_write - helper for writing data to a loop device + * + * This is the fast, non-transforming version for backing filesystems which do + * not implement the address space operations prepare_write and commit_write. + * It uses the write file operation which should be present on all writeable + * filesystems. + */ +static int do_lo_send_direct_write(struct loop_device *lo, + struct bio_vec *bvec, int bsize, loff_t pos, struct page *page) +{ + ssize_t bw = __do_lo_send_write(lo->lo_backing_file, + (u8 __user *)kmap(bvec->bv_page) + bvec->bv_offset, + bvec->bv_len, pos); + kunmap(bvec->bv_page); + cond_resched(); + return bw; +} + +/** + * do_lo_send_write - helper for writing data to a loop device + * + * This is the slow, transforming version for filesystems which do not + * implement the address space operations prepare_write and commit_write. It + * uses the write file operation which should be present on all writeable + * filesystems. + * + * Using fops->write is slower than using aops->{prepare,commit}_write in the + * transforming case because we need to double buffer the data as we cannot do + * the transformations in place as we do not have direct access to the + * destination pages of the backing file. + */ +static int do_lo_send_write(struct loop_device *lo, struct bio_vec *bvec, + int bsize, loff_t pos, struct page *page) +{ + int ret = lo_do_transfer(lo, WRITE, page, 0, bvec->bv_page, + bvec->bv_offset, bvec->bv_len, pos >> 9); + if (likely(!ret)) + return __do_lo_send_write(lo->lo_backing_file, + (u8 __user *)page_address(page), bvec->bv_len, + pos); + printk(KERN_ERR "loop: Transfer error at byte offset %llu, " + "length %i.\n", (unsigned long long)pos, bvec->bv_len); + if (ret > 0) + ret = -EIO; + return ret; +} + +static int lo_send(struct loop_device *lo, struct bio *bio, int bsize, + loff_t pos) +{ + int (*do_lo_send)(struct loop_device *, struct bio_vec *, int, loff_t, + struct page *page); struct bio_vec *bvec; + struct page *page = NULL; int i, ret = 0; + do_lo_send = do_lo_send_aops; + if (!(lo->lo_flags & LO_FLAGS_USE_AOPS)) { + do_lo_send = do_lo_send_direct_write; + if (lo->transfer != transfer_none) { + page = alloc_page(GFP_NOIO | __GFP_HIGHMEM); + if (unlikely(!page)) + goto fail; + kmap(page); + do_lo_send = do_lo_send_write; + } + } bio_for_each_segment(bvec, bio, i) { - ret = do_lo_send(lo, bvec, bsize, pos); + ret = do_lo_send(lo, bvec, bsize, pos, page); if (ret < 0) break; pos += bvec->bv_len; } + if (page) { + kunmap(page); + __free_page(page); + } +out: return ret; +fail: + printk(KERN_ERR "loop: Failed to allocate temporary page for write.\n"); + ret = -ENOMEM; + goto out; } struct lo_read_data { @@ -584,7 +688,7 @@ static int loop_change_fd(struct loop_device *lo, struct file *lo_file, /* the loop device has to be read-only */ error = -EINVAL; - if (lo->lo_flags != LO_FLAGS_READ_ONLY) + if (!(lo->lo_flags & LO_FLAGS_READ_ONLY)) goto out; error = -EBADF; @@ -683,8 +787,9 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file, */ if (!file->f_op->sendfile) goto out_putf; - - if (!aops->prepare_write || !aops->commit_write) + if (aops->prepare_write && aops->commit_write) + lo_flags |= LO_FLAGS_USE_AOPS; + if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write) lo_flags |= LO_FLAGS_READ_ONLY; lo_blocksize = inode->i_blksize; @@ -1137,7 +1242,7 @@ int loop_unregister_transfer(int number) EXPORT_SYMBOL(loop_register_transfer); EXPORT_SYMBOL(loop_unregister_transfer); -int __init loop_init(void) +static int __init loop_init(void) { int i; @@ -1212,7 +1317,7 @@ out_mem1: return -ENOMEM; } -void loop_exit(void) +static void loop_exit(void) { int i;