Commit 8b8b08cb authored Jul 19, 2016 by Chris Mason

Btrfs: fix delalloc accounting after copy_from_user faults



Commit 56244ef1 was almost but not quite enough to fix the
reservation math after btrfs_copy_from_user returned partial copies.

Some users are still seeing warnings in btrfs_destroy_inode, and with a
long enough test run I'm able to trigger them as well.

This patch fixes the accounting math again, bringing it much closer to
the way it was before the sectorsize conversion Chandan did.  The
problem is accounting for the offset into the page/sector when we do a
partial copy.  This one just uses the dirty_sectors variable which
should already be updated properly.

Signed-off-by: Chris Mason <clm@fb.com>
cc: stable@vger.kernel.org # v4.6+

parent bac357dc

fs/btrfs/file.c

+5 −7

Original line number	Diff line number	Diff line
		@@ -1629,13 +1629,11 @@ again:
		* managed to copy.
		*/
		if (num_sectors > dirty_sectors) {
		/*
		* we round down because we don't want to count
		* any partial blocks actually sent through the
		* IO machines
		*/
		release_bytes = round_down(release_bytes - copied,
		root->sectorsize);

		/* release everything except the sectors we dirtied */
		release_bytes -= dirty_sectors <<
		root->fs_info->sb->s_blocksize_bits;

		if (copied > 0) {
		spin_lock(&BTRFS_I(inode)->lock);
		BTRFS_I(inode)->outstanding_extents++;

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