diff options
authorDavid Sterba <>2015-04-17 18:20:32 +0200
committerDavid Sterba <>2015-04-22 18:21:47 +0200
commite57dc6c753e5eb1ed240ffefee7c80e22da08999 (patch)
parent7ffccaf0c3b4d4979d7d74bab3d79d9541a6e665 (diff)
btrfs-progs: fi resize: accept only directories as paths
Resize of a filesystem image does not work as expected. This has been confusing and can have bad consequences as people have reported, resizing the wrong filesystem. Signed-off-by: David Sterba <>
2 files changed, 22 insertions, 2 deletions
diff --git a/Documentation/btrfs-filesystem.asciidoc b/Documentation/btrfs-filesystem.asciidoc
index cefdc8ea..f1c35b67 100644
--- a/Documentation/btrfs-filesystem.asciidoc
+++ b/Documentation/btrfs-filesystem.asciidoc
@@ -89,8 +89,13 @@ NOTE: the maximum allowable length shall be less than 256 chars
// Some wording are extracted by the resize2fs man page
*resize* [<devid>:][+/-]<size>[kKmMgGtTpPeE]|[<devid>:]max <path>::
-Resize a filesystem identified by <path> for the underlying device
-devid *online*. +
+Resize a mounted filesystem identified by directory <path>. A particular device
+can be resized by specifying a <devid>.
+If <path> is a file containing a btrfs image then resize does not work as
+expected and does not resize the image. This would resize the underlying
+filesystem instead.
The devid can be found with *btrfs filesystem show* and
defaults to 1 if not specified.
The <size> parameter specifies the new size of the filesystem.
diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index 188dbf0c..c9a34e4d 100644
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -1234,6 +1234,7 @@ static int cmd_resize(int argc, char **argv)
int fd, res, len, e;
char *amount, *path;
DIR *dirstream = NULL;
+ struct stat st;
if (check_argc_exact(argc, 3))
@@ -1248,6 +1249,20 @@ static int cmd_resize(int argc, char **argv)
return 1;
+ res = stat(path, &st);
+ if (res < 0) {
+ fprintf(stderr, "ERROR: resize: cannot stat %s: %s\n",
+ path, strerror(errno));
+ return 1;
+ }
+ if (!S_ISDIR(st.st_mode)) {
+ fprintf(stderr,
+ "ERROR: resize works on mounted filesystems and accepts only\n"
+ "directories as argument. Passing file containing a btrfs image\n"
+ "would resize the underlying filesystem instead of the image.\n");
+ return 1;
+ }
fd = open_file_or_dir(path, &dirstream);
if (fd < 0) {
fprintf(stderr, "ERROR: can't access '%s'\n", path);