[RFC] btrfs-progs: require mkfs -f force option to overwrite filesystem or partition table

Message ID	511D2D2B.8040804@redhat.com (mailing list archive)
State	Accepted, archived
Headers	show Return-Path: <linux-btrfs-owner@vger.kernel.org> Message-ID: <511D2D2B.8040804@redhat.com> Date: Thu, 14 Feb 2013 12:30:03 -0600 From: Eric Sandeen <sandeen@redhat.com> User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130107 Thunderbird/17.0.2 MIME-Version: 1.0 To: linux-btrfs <linux-btrfs@vger.kernel.org> Subject: [PATCH, RFC] btrfs-progs: require mkfs -f force option to overwrite filesystem or partition table Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk

diff --git a/Makefile b/Makefile index 4894903..bd0e8a6 100644 --- a/Makefile +++ b/Makefile @@ -17,7 +17,7 @@ DEPFLAGS = -Wp,-MMD,$(@D)/.$(@F).d,-MT,$@ INSTALL = install prefix ?= /usr/local bindir = $(prefix)/bin -LIBS=-luuid -lm +LIBS=-luuid -lblkid -lm RESTORE_LIBS=-lz progs = btrfsctl mkfs.btrfs btrfs-debug-tree btrfs-show btrfs-vol btrfsck \ diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in index c9f9e4f..9188201 100644 --- a/man/mkfs.btrfs.8.in +++ b/man/mkfs.btrfs.8.in @@ -6,6 +6,7 @@ mkfs.btrfs \- create a btrfs filesystem [ \fB\-A\fP\fI alloc-start\fP ] [ \fB\-b\fP\fI byte-count\fP ] [ \fB\-d\fP\fI data-profile\fP ] +[ \fB\-f\fP\fI ] [ \fB\-l\fP\fI leafsize\fP ] [ \fB\-L\fP\fI label\fP ] [ \fB\-m\fP\fI metadata profile\fP ] @@ -38,6 +39,11 @@ mkfs.btrfs uses all the available storage for the filesystem. Specify how the data must be spanned across the devices specified. Valid values are raid0, raid1, raid10 or single. .TP +\fB\-f\fR +Force overwrite when an existing filesystem is detected on the device. +By default, mkfs.btrfs will not write to the device if it suspects that +there is a filesystem or partition table on the device already. +.TP \fB\-l\fR, \fB\-\-leafsize \fIsize\fR Specify the leaf size, the least data item in which btrfs stores data. The default value is the page size. diff --git a/mkfs.c b/mkfs.c index 129fae8..207066c 100644 --- a/mkfs.c +++ b/mkfs.c @@ -39,6 +39,7 @@ #include <linux/fs.h> #include <ctype.h> #include <attr/xattr.h> +#include <blkid/blkid.h> #include "ctree.h" #include "disk-io.h" #include "volumes.h" @@ -1162,6 +1163,86 @@ static int check_leaf_or_node_size(u32 size, u32 sectorsize) return 0; } +/* + * Check for existing filesystem or partition table on device. + * Returns: + * 1 for existing fs or partition + * 0 for nothing found + * -1 for internal error + */ +static int +check_overwrite( + char *device) +{ + const char *type; + blkid_probe pr = NULL; + int ret; + blkid_loff_t size; + + if (!device || !*device) + return 0; + + ret = -1; /* will reset on success of all setup calls */ + + pr = blkid_new_probe_from_filename(device); + if (!pr) + goto out; + + size = blkid_probe_get_size(pr); + if (size < 0) + goto out; + + /* nothing to overwrite on a 0-length device */ + if (size == 0) { + ret = 0; + goto out; + } + + ret = blkid_probe_enable_partitions(pr, 1); + if (ret < 0) + goto out; + + ret = blkid_do_fullprobe(pr); + if (ret < 0) + goto out; + + /* + * Blkid returns 1 for nothing found and 0 when it finds a signature, + * but we want the exact opposite, so reverse the return value here. + * + * In addition print some useful diagnostics about what actually is + * on the device. + */ + if (ret) { + ret = 0; + goto out; + } + + if (!blkid_probe_lookup_value(pr, "TYPE", &type, NULL)) { + fprintf(stderr, + "%s appears to contain an existing " + "filesystem (%s).\n", device, type); + } else if (!blkid_probe_lookup_value(pr, "PTTYPE", &type, NULL)) { + fprintf(stderr, + "%s appears to contain a partition " + "table (%s).\n", device, type); + } else { + fprintf(stderr, + "%s appears to contain something weird " + "according to blkid\n", device); + } + ret = 1; + +out: + if (pr) + blkid_free_probe(pr); + if (ret == -1) + fprintf(stderr, + "probe of %s failed, cannot detect " + "existing filesystem.\n", device); + return ret; +} + int main(int ac, char **av) { char *file; @@ -1188,6 +1269,7 @@ int main(int ac, char **av) int data_profile_opt = 0; int metadata_profile_opt = 0; int nodiscard = 0; + int force_overwrite = 0; char *source_dir = NULL; int source_dir_set = 0; @@ -1198,7 +1280,7 @@ int main(int ac, char **av) while(1) { int c; - c = getopt_long(ac, av, "A:b:l:n:s:m:d:L:r:VMK", long_options, + c = getopt_long(ac, av, "A:b:fl:n:s:m:d:L:r:VMK", long_options, &option_index); if (c < 0) break; @@ -1206,6 +1288,9 @@ int main(int ac, char **av) case 'A': alloc_start = parse_size(optarg); break; + case 'f': + force_overwrite = 1; + break; case 'd': data_profile = parse_profile(optarg); data_profile_opt = 1; @@ -1272,6 +1357,13 @@ int main(int ac, char **av) file = av[optind++]; ac--; /* used that arg */ + if (!force_overwrite) { + if (check_overwrite(file)) { + fprintf(stderr, "Use the -f option to force overwrite.\n"); + exit(1); + } + } + ret = check_mounted(file); if (ret < 0) { fprintf(stderr, "error checking %s mount status\n", file); @@ -1375,6 +1467,13 @@ int main(int ac, char **av) int old_mixed = mixed; file = av[optind++]; + if (!force_overwrite) { + if (check_overwrite(file)) { + fprintf(stderr, "Use the -f option to force overwrite.\n"); + exit(1); + } + } + ret = check_mounted(file); if (ret < 0) { fprintf(stderr, "error checking %s mount status\n",

[RFC] btrfs-progs: require mkfs -f force option to overwrite filesystem or partition table

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