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Date: Thu, 22 Apr 2010 22:33:58 +0200
From: Jörn Engel <joern@...fs.org>
To: Jens Axboe <jens.axboe@...cle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
David Woodhouse <dwmw2@...radead.org>,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
Christoph Hellwig <hch@...radead.org>
Subject: [Patch] Catch filesystems lacking s_bdi
On Thu, 22 April 2010 18:27:10 +0200, Jens Axboe wrote:
>
> > Jens - please help fix this up.
>
> Of course, I already posted a series of patches to fix this up. I want
> to test them a bit, and I'll send them in tomorrow.
How about something like this to catch future cases? It compiles and
survived a test boot, so it does seem to work for the common cases like
tmpfs, procfs, etc.
Jens, you know the bdi code 10x better than me, would this work?
Jörn
--
ticks = jiffies;
while (ticks == jiffies);
ticks = jiffies;
-- /usr/src/linux/init/main.c
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@...fs.org>
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 @@ int set_anon_super(struct super_block *s, void *data)
return -EMFILE;
}
s->s_dev = MKDEV(0, dev & MINORMASK);
+ s->s_bdi = &noop_backing_dev_info;
return 0;
}
@@ -954,10 +955,11 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
if (error < 0)
goto out_free_secdata;
BUG_ON(!mnt->mnt_sb);
+ BUG_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 @@ static int __sync_filesystem(struct super_block *sb, int wait)
* 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 fcbc26a..f4a1436 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -246,6 +246,7 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
#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 f13e067..4aba836 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -25,6 +25,11 @@ struct backing_dev_info default_backing_dev_info = {
};
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;
/*
--
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