Using get_active_super will not work properly if the fs (like btrfs) does not
save it's s_bdev with the device it is on. Also it doesn't provide the entire
picture, since an fs can be contained on multiple disks (again like btrfs). So
add a super operation that will check to see if the given block device is
contained within the given super. This will mean that if we try to something
like a snapshot of a lv with btrfs on the lv the fs will actually get properly
frozen. Thanks,
Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
---
Documentation/filesystems/vfs.txt | 6 ++++++
fs/super.c | 16 ++++++++++++++--
include/linux/fs.h | 1 +
3 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 94cf97b..ce22988 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -221,6 +221,7 @@ struct super_operations {
ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
+ int (*contains_bdev)(struct super_block *, struct block_device *);
};
All methods are called without any locks being held, unless otherwise
@@ -293,6 +294,11 @@ or bottom half).
quota_write: called by the VFS to write to filesystem quota file.
+ contains_bdev: called by the VFS to see if the filesystem contains the given
+ block_device. Return 1 if it does or 0 if it does not. Only intended
+ for filesystems that can have several underlying block devices.
+ Optional.
+
Whoever sets up the inode is responsible for filling in the "i_op" field. This
is a pointer to a "struct inode_operations" which describes the methods that
can be performed on individual inodes.
diff --git a/fs/super.c b/fs/super.c
index 7e9dd4c..43185fa 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -497,7 +497,7 @@ EXPORT_SYMBOL(get_super);
*/
struct super_block *get_active_super(struct block_device *bdev)
{
- struct super_block *sb;
+ struct super_block *sb, *p = NULL;
if (!bdev)
return NULL;
@@ -507,13 +507,25 @@ restart:
list_for_each_entry(sb, &super_blocks, s_list) {
if (list_empty(&sb->s_instances))
continue;
- if (sb->s_bdev == bdev) {
+
+ if (sb->s_op->contains_bdev) {
+ if (!grab_super(sb))
+ goto restart;
+ if (sb->s_op->contains_bdev(sb, bdev))
+ return sb;
+ spin_lock(&sb_lock);
+ if (p)
+ __put_super(p);
+ p = sb;
+ } else if (sb->s_bdev == bdev) {
if (grab_super(sb)) /* drops sb_lock */
return sb;
else
goto restart;
}
}
+ if (p)
+ __put_super(p);
spin_unlock(&sb_lock);
return NULL;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e38b50a..fe12b7b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1627,6 +1627,7 @@ struct super_operations {
ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
#endif
int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
+ int (*contains_bdev)(struct super_block *, struct block_device *);
};
/*
--
1.7.2.3
--
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