3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
commit 3a2d63f87989e01437ba994df5f297528c353d7d upstream.
There are two problems with shutdown in the NBD driver.
1: Receiving the NBD_DISCONNECT ioctl does not sync the filesystem.
This patch adds the sync operation into __nbd_ioctl()'s
NBD_DISCONNECT handler. This is useful because BLKFLSBUF is restricted
to processes that have CAP_SYS_ADMIN, and the NBD client may not
possess it (fsync of the block device does not sync the filesystem,
either).
2: Once we clear the socket we have no guarantee that later reads will
come from the same backing storage.
The patch adds calls to kill_bdev() in __nbd_ioctl()'s socket
clearing code so the page cache is cleaned, lest reads that hit on the
page cache will return stale data from the previously-accessible disk.
Example:
# qemu-nbd -r -c/dev/nbd0 /dev/sr0
# file -s /dev/nbd0
/dev/stdin: # UDF filesystem data (version 1.5) etc.
# qemu-nbd -d /dev/nbd0
# qemu-nbd -r -c/dev/nbd0 /dev/sda
# file -s /dev/nbd0
/dev/stdin: # UDF filesystem data (version 1.5) etc.
While /dev/sda has:
# file -s /dev/sda
/dev/sda: x86 boot sector; etc.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Acked-by: Paul Clements <Paul.Clements@xxxxxxxxxxxx>
Cc: Alex Bligh <alex@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjusted context
- s/\bnbd\b/lo/
- Incorporate export of kill_bdev() from commit ff01bb483265
('fs: move code out of buffer.c')]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -584,12 +584,20 @@ static int __nbd_ioctl(struct block_devi
struct request sreq;
dev_info(disk_to_dev(lo->disk), "NBD_DISCONNECT\n");
+ if (!lo->sock)
+ return -EINVAL;
+ mutex_unlock(&lo->tx_lock);
+ fsync_bdev(bdev);
+ mutex_lock(&lo->tx_lock);
blk_rq_init(NULL, &sreq);
sreq.cmd_type = REQ_TYPE_SPECIAL;
nbd_cmd(&sreq) = NBD_CMD_DISC;
+
+ /* Check again after getting mutex back. */
if (!lo->sock)
return -EINVAL;
+
nbd_send_req(lo, &sreq);
return 0;
}
@@ -603,6 +611,7 @@ static int __nbd_ioctl(struct block_devi
nbd_clear_que(lo);
BUG_ON(!list_empty(&lo->queue_head));
BUG_ON(!list_empty(&lo->waiting_queue));
+ kill_bdev(bdev);
if (file)
fput(file);
return 0;
@@ -683,6 +692,7 @@ static int __nbd_ioctl(struct block_devi
lo->file = NULL;
nbd_clear_que(lo);
dev_warn(disk_to_dev(lo->disk), "queue cleared\n");
+ kill_bdev(bdev);
if (file)
fput(file);
lo->bytesize = 0;
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -82,13 +82,14 @@ sector_t blkdev_max_block(struct block_d
}
/* Kill _all_ buffers and pagecache , dirty or not.. */
-static void kill_bdev(struct block_device *bdev)
+void kill_bdev(struct block_device *bdev)
{
if (bdev->bd_inode->i_mapping->nrpages == 0)
return;
invalidate_bh_lrus();
truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
}
+EXPORT_SYMBOL(kill_bdev);
int set_blocksize(struct block_device *bdev, int size)
{
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2103,6 +2103,7 @@ extern void bd_forget(struct inode *inod
extern void bdput(struct block_device *);
extern void invalidate_bdev(struct block_device *);
extern int sync_blockdev(struct block_device *bdev);
+extern void kill_bdev(struct block_device *);
extern struct super_block *freeze_bdev(struct block_device *);
extern void emergency_thaw_all(void);
extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
@@ -2110,6 +2111,7 @@ extern int fsync_bdev(struct block_devic
#else
static inline void bd_forget(struct inode *inode) {}
static inline int sync_blockdev(struct block_device *bdev) { return 0; }
+static inline void kill_bdev(struct block_device *bdev) {}
static inline void invalidate_bdev(struct block_device *bdev) {}
static inline struct super_block *freeze_bdev(struct block_device *sb)
--
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