Catch filesystems lacking s_bdi
noop_backing_dev_info is used only as a flag to mark filesystems that
don't have any backing store, like tmpfs, procfs, spufs, etc.
Signed-off-by: Joern Engel <joern@logfs.org>
Changed the BUG_ON() to a WARN_ON(). Note that adding dirty inodes
to the noop_backing_dev_info is not legal and will not result in
them being flushed, but we already catch this condition in
__mark_inode_dirty() when checking for a registered bdi.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/super.c b/fs/super.c
index f35ac60..dc72491 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -693,6 +693,7 @@
return -EMFILE;
}
s->s_dev = MKDEV(0, dev & MINORMASK);
+ s->s_bdi = &noop_backing_dev_info;
return 0;
}
@@ -954,10 +955,11 @@
if (error < 0)
goto out_free_secdata;
BUG_ON(!mnt->mnt_sb);
+ WARN_ON(!mnt->mnt_sb->s_bdi);
- error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
- if (error)
- goto out_sb;
+ error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
+ if (error)
+ goto out_sb;
/*
* filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
diff --git a/fs/sync.c b/fs/sync.c
index fc5c3d7..92b2281 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -14,6 +14,7 @@
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
+#include <linux/backing-dev.h>
#include "internal.h"
#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
@@ -32,7 +33,7 @@
* This should be safe, as we require bdi backing to actually
* write out data in the first place
*/
- if (!sb->s_bdi)
+ if (!sb->s_bdi || sb->s_bdi == &noop_backing_dev_info)
return 0;
if (sb->s_qcop && sb->s_qcop->quota_sync)
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index e19c677..bd0e3c6 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -247,6 +247,7 @@
#endif
extern struct backing_dev_info default_backing_dev_info;
+extern struct backing_dev_info noop_backing_dev_info;
void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
int writeback_in_progress(struct backing_dev_info *bdi);
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index dbda470..707d0dc6 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -27,6 +27,11 @@
};
EXPORT_SYMBOL_GPL(default_backing_dev_info);
+struct backing_dev_info noop_backing_dev_info = {
+ .name = "noop",
+};
+EXPORT_SYMBOL_GPL(noop_backing_dev_info);
+
static struct class *bdi_class;
/*
