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Commit 0cb80b48 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

dax: Fix sleep in atomic contex in grab_mapping_entry() 



Commit 642261ac: "dax: add struct iomap based DAX PMD support" has
introduced unmapping of page tables if huge page needs to be split in
grab_mapping_entry(). However the unmapping happens after
radix_tree_preload() call which disables preemption and thus
unmap_mapping_range() tries to acquire i_mmap_lock in atomic context
which is a bug. Fix the problem by moving unmapping before
radix_tree_preload() call.

Fixes: 642261ac
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 73b92a2a

fs/dax.c

+7 −8
Original line number Diff line number Diff line
@@ -333,14 +333,6 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index, 
		}



		spin_unlock_irq(&mapping->tree_lock);

		err = radix_tree_preload(

				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);

		if (err) {

			if (pmd_downgrade)

				put_locked_mapping_entry(mapping, index, entry);

			return ERR_PTR(err);

		}



		/*

		 * Besides huge zero pages the only other thing that gets

		 * downgraded are empty entries which don't need to be
@@ -350,6 +342,13 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index, 
			unmap_mapping_range(mapping,

				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);



		err = radix_tree_preload(

				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);

		if (err) {

			if (pmd_downgrade)

				put_locked_mapping_entry(mapping, index, entry);

			return ERR_PTR(err);

		}

		spin_lock_irq(&mapping->tree_lock);



		if (pmd_downgrade) {