md/bitmap: don't abuse i_writecount for bitmap files.
md bitmap code currently tries to use i_writecount to stop any other
process from writing to out bitmap file. But that is really an abuse
and has bit-rotted so locking is all wrong.
So discard that - root should be allowed to shoot self in foot.
Still use it in a much less intrusive way to stop the same file being
used as bitmap on two different array, and apply other checks to
ensure the file is at least vaguely usable for bitmap storage
(is regular, is open for write. Support for ->bmap is already checked
elsewhere).
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4ad5cc4..3fa2fc0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5181,32 +5181,6 @@
return 0;
}
-/* similar to deny_write_access, but accounts for our holding a reference
- * to the file ourselves */
-static int deny_bitmap_write_access(struct file * file)
-{
- struct inode *inode = file->f_mapping->host;
-
- spin_lock(&inode->i_lock);
- if (atomic_read(&inode->i_writecount) > 1) {
- spin_unlock(&inode->i_lock);
- return -ETXTBSY;
- }
- atomic_set(&inode->i_writecount, -1);
- spin_unlock(&inode->i_lock);
-
- return 0;
-}
-
-void restore_bitmap_write_access(struct file *file)
-{
- struct inode *inode = file->f_mapping->host;
-
- spin_lock(&inode->i_lock);
- atomic_set(&inode->i_writecount, 1);
- spin_unlock(&inode->i_lock);
-}
-
static void md_clean(struct mddev *mddev)
{
mddev->array_sectors = 0;
@@ -5427,7 +5401,6 @@
bitmap_destroy(mddev);
if (mddev->bitmap_info.file) {
- restore_bitmap_write_access(mddev->bitmap_info.file);
fput(mddev->bitmap_info.file);
mddev->bitmap_info.file = NULL;
}
@@ -5979,7 +5952,7 @@
static int set_bitmap_file(struct mddev *mddev, int fd)
{
- int err;
+ int err = 0;
if (mddev->pers) {
if (!mddev->pers->quiesce)
@@ -5991,6 +5964,7 @@
if (fd >= 0) {
+ struct inode *inode;
if (mddev->bitmap)
return -EEXIST; /* cannot add when bitmap is present */
mddev->bitmap_info.file = fget(fd);
@@ -6001,10 +5975,21 @@
return -EBADF;
}
- err = deny_bitmap_write_access(mddev->bitmap_info.file);
- if (err) {
+ inode = mddev->bitmap_info.file->f_mapping->host;
+ if (!S_ISREG(inode->i_mode)) {
+ printk(KERN_ERR "%s: error: bitmap file must be a regular file\n",
+ mdname(mddev));
+ err = -EBADF;
+ } else if (!(mddev->bitmap_info.file->f_mode & FMODE_WRITE)) {
+ printk(KERN_ERR "%s: error: bitmap file must open for write\n",
+ mdname(mddev));
+ err = -EBADF;
+ } else if (atomic_read(&inode->i_writecount) != 1) {
printk(KERN_ERR "%s: error: bitmap file is already in use\n",
mdname(mddev));
+ err = -EBUSY;
+ }
+ if (err) {
fput(mddev->bitmap_info.file);
mddev->bitmap_info.file = NULL;
return err;
@@ -6027,10 +6012,8 @@
mddev->pers->quiesce(mddev, 0);
}
if (fd < 0) {
- if (mddev->bitmap_info.file) {
- restore_bitmap_write_access(mddev->bitmap_info.file);
+ if (mddev->bitmap_info.file)
fput(mddev->bitmap_info.file);
- }
mddev->bitmap_info.file = NULL;
}