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authorJon Derrick <jonathan.derrick@intel.com>2018-07-02 18:45:18 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-07-11 16:31:31 +0200
commitc2b9dc3f6e9402026bc0e2cd122ef02673153d50 (patch)
parenta5f8b0a70e3967ec2e5b91dfc865d10fb995f37d (diff)
ext4: check superblock mapped prior to committing
commit a17712c8e4be4fa5404d20e9cd3b2b21eae7bc56 upstream. This patch attempts to close a hole leading to a BUG seen with hot removals during writes [1]. A block device (NVME namespace in this test case) is formatted to EXT4 without partitions. It's mounted and write I/O is run to a file, then the device is hot removed from the slot. The superblock attempts to be written to the drive which is no longer present. The typical chain of events leading to the BUG: ext4_commit_super() __sync_dirty_buffer() submit_bh() submit_bh_wbc() BUG_ON(!buffer_mapped(bh)); This fix checks for the superblock's buffer head being mapped prior to syncing. [1] https://www.spinics.net/lists/linux-ext4/msg56527.html Signed-off-by: Jon Derrick <jonathan.derrick@intel.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 8 insertions, 0 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f6b9c332b5b6..6962d622c6ba 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4763,6 +4763,14 @@ static int ext4_commit_super(struct super_block *sb, int sync)
if (!sbh || block_device_ejected(sb))
return error;
+ /*
+ * The superblock bh should be mapped, but it might not be if the
+ * device was hot-removed. Not much we can do but fail the I/O.
+ */
+ if (!buffer_mapped(sbh))
+ return error;
* If the file system is mounted read-only, don't update the
* superblock write time. This avoids updating the superblock