The patch titled
blkdev: flush disk cache on ->fsync
has been added to the -mm tree. Its filename is
blkdev-flush-disk-cache-on-fsync.patch
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------------------------------------------------------
Subject: blkdev: flush disk cache on ->fsync
From: Christoph Hellwig <hch@xxxxxx>
Currently there is no barrier support in the block device code. That
means we cannot guarantee any sort of data integrity when using the block
device node with dis kwrite caches enabled. Using the raw block device
node is a typical use case for virtualization (and I assume databases,
too). This patch changes block_fsync to issue a cache flush and thus make
fsync on block device nodes actually useful.
Note that in mainline we would also need to add such code to the
->aio_write method for O_SYNC handling, but assuming that Jan's patch
series for the O_SYNC rewrite goes in it will also call into ->fsync for
2.6.32.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/block_dev.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff -puN fs/block_dev.c~blkdev-flush-disk-cache-on-fsync fs/block_dev.c
--- a/fs/block_dev.c~blkdev-flush-disk-cache-on-fsync
+++ a/fs/block_dev.c
@@ -405,7 +405,17 @@ static loff_t block_llseek(struct file *
static int block_fsync(struct file *filp, struct dentry *dentry, int datasync)
{
- return sync_blockdev(I_BDEV(filp->f_mapping->host));
+ struct block_device *bdev = I_BDEV(filp->f_mapping->host);
+ int error;
+
+ error = sync_blockdev(bdev);
+ if (error)
+ return error;
+
+ error = blkdev_issue_flush(bdev, NULL);
+ if (error == -EOPNOTSUPP)
+ error = 0;
+ return error;
}
/*
_
Patches currently in -mm which might be from hch@xxxxxx are
origin.patch
linux-next.patch
avr32-convert-to-asm-generic-hardirqh.patch
vfs-fix-vfs_rename_dir-for-fs_rename_does_d_move-filesystems.patch
fs-remove-unneeded-dcache_unhashed-tricks.patch
xtensa-convert-to-asm-generic-hardirqh.patch
vfs-implement-posix-o_sync-and-o_dsync-semantics.patch
qnx4fs-remove-remains-of-the-defunct-write-support.patch
blkdev-flush-disk-cache-on-fsync.patch
elf-kill-use_elf_core_dump.patch
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