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Commit a17712c8 authored by Jon Derrick's avatar Jon Derrick Committed by Theodore Ts'o
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ext4: check superblock mapped prior to committing

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: default avatarJon Derrick <jonathan.derrick@intel.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
parent bfe0a5f4
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