Messages in this thread Patch in this message | | | Date | Wed, 25 Mar 2009 17:29:23 -0400 | From | Jeff Garzik <> | Subject | [PATCH] issue storage device flush via sync_blockdev() (was Re: Linux 2.6.29) |
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On Wed, Mar 25, 2009 at 01:40:37PM -0700, Linus Torvalds wrote: > On Wed, 25 Mar 2009, Jeff Garzik wrote: > > It is clearly possible to implement an fsync(2) that causes FLUSH CACHE to be > > issued, without adding full barrier support to a filesystem. It is likely > > doable to avoid touching per-filesystem code at all, if we issue the flush > > from a generic fsync(2) code path in the kernel. > > We could easily do that. It would even work for most cases. The > problematic ones are where filesystems do their own disk management, but I > guess those people can do their own fsync() management too. > > Somebody send me the patch, we can try it out.
This is a simple step that would cover a lot of cases... sync(2) calls sync_blockdev(), and many filesystems do as well via the generic filesystem helper file_fsync (fs/sync.c).
XFS code calls sync_blockdev() a "big hammer", so I hope my patch follows with known practice.
Looking over every use of sync_blockdev(), its most frequent use is through fsync(2), for the selected filesystems that use the generic file_fsync helper.
Most callers of sync_blockdev() in the kernel do so infrequently, when removing and invalidating volumes (MD) or storing the superblock prior to release (put_super) in some filesystems.
Compile-tested only, of course :) But it should be work :)
My main concern is some hidden area that calls sync_blockdev() with a high-enough frequency that the performance hit is bad.
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/fs/buffer.c b/fs/buffer.c index 891e1c7..7b9f74a 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -173,9 +173,14 @@ int sync_blockdev(struct block_device *bdev) { int ret = 0; - if (bdev) - ret = filemap_write_and_wait(bdev->bd_inode->i_mapping); - return ret; + if (!bdev) + return 0; + + ret = filemap_write_and_wait(bdev->bd_inode->i_mapping); + if (ret) + return ret; + + return blkdev_issue_flush(bdev, NULL); } EXPORT_SYMBOL(sync_blockdev);
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