From 0cb80b4847553582830a59da2c022c37a1f4a119 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 12 Dec 2016 21:34:12 -0500 Subject: [PATCH] dax: Fix sleep in atomic contex in grab_mapping_entry() Commit 642261ac995e: "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: 642261ac995e01d7837db1f4b90181496f7e6835 Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o --- fs/dax.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index ad131cd2605d..5bfd27b4a69c 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -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) {