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Commit 5b92ee72 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Fix lock ordering of the snapshot semaphore against the page lock 



Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent bd09835d

fs/btrfs/file.c

+4 −2
Original line number Diff line number Diff line
@@ -251,7 +251,6 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans, 
	num_bytes = (write_bytes + pos - start_pos +

		    root->sectorsize - 1) & ~((u64)root->sectorsize - 1);



	down_read(&BTRFS_I(inode)->root->snap_sem);

	end_of_last_block = start_pos + num_bytes - 1;



	lock_extent(em_tree, start_pos, end_of_last_block, GFP_NOFS);
@@ -356,7 +355,6 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans, 
	mutex_unlock(&root->fs_info->fs_mutex);

	unlock_extent(em_tree, start_pos, end_of_last_block, GFP_NOFS);

	free_extent_map(em);

	up_read(&BTRFS_I(inode)->root->snap_sem);

	return err;

}
@@ -726,6 +724,8 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf, 


	pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);



	down_read(&BTRFS_I(inode)->root->snap_sem);



	mutex_lock(&inode->i_mutex);

	first_index = pos >> PAGE_CACHE_SHIFT;

	last_index = (pos + count) >> PAGE_CACHE_SHIFT;
@@ -804,6 +804,8 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf, 
	}

out:

	mutex_unlock(&inode->i_mutex);

	up_read(&BTRFS_I(inode)->root->snap_sem);



out_nolock:

	kfree(pages);

	if (pinned[0])