3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: Paolo Bonzini <pbonz...@redhat.com> 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 <pbonz...@redhat.com> Acked-by: Paul Clements <paul.cleme...@steeleye.com> Cc: Alex Bligh <a...@alex.org.uk> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> [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 <b...@decadent.org.uk> --- --- 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) -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html