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29 July 2024, 15:18:00 UTC
Revision 05bf86b4ccfd0f197da61c67bd372111d15a6620 authored by Hugh Dickins on 14 May 2011, 19:06:42 UTC, committed by Linus Torvalds on 14 May 2011, 19:18:55 UTC 
tmpfs: fix race between swapoff and writepage
 
Shame on me!  Commit b1dea800ac39 "tmpfs: fix race between umount and
writepage" fixed the advertized race, but introduced another: as even
its comment makes clear, we cannot safely rely on a peek at list_empty()
while holding no lock - until info->swapped is set, shmem_unuse_inode()
may delete any formerly-swapped inode from the shmem_swaplist, which
in this case would leave a swap area impossible to swapoff.

Although I don't relish taking the mutex every time, I don't care much
for the alternatives either; and at least the peek at list_empty() in
shmem_evict_inode() (a hotter path since most inodes would never have
been swapped) remains safe, because we already truncated the whole file.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent afa4979
History
Tip revision: 05bf86b4ccfd0f197da61c67bd372111d15a6620 authored by Hugh Dickins on 14 May 2011, 19:06:42 UTC
tmpfs: fix race between swapoff and writepage
Tip revision: 05bf86b
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