Hi Linus,
Could you pull these fixes for the netfs lib? There are two:
(1) Fix a lockdep warning and potential deadlock. This is takes the
simple approach of offloading the write-to-cache done from within a
network filesystem read to a worker thread to avoid taking the
sb_writer lock from the cache backing filesystem whilst holding the
mmap lock on an inode from the network filesystem.
Jan Kara posits a scenario whereby this can cause deadlock[1], though
it's quite complex and I think requires someone in userspace to
actually do I/O on the cache files. Matthew Wilcox isn't so certain,
though[2].
An alternative way to fix this, suggested by Darrick Wong, might be to
allow cachefiles to prevent userspace from performing I/O upon the
file - something like an exclusive open - but that's beyond the scope
of a fix here if we do want to make such a facility in the future.
(2) In some of the error handling paths where netfs_ops->cleanup() is
called, the arguments are transposed[3]. gcc doesn't complain because
one of the parameters is void* and one of the values is void*.
David
Link: https://lore.kernel.org/r/20210922110420.GA21576@xxxxxxxxxxxxxx/ [1]
Link: https://lore.kernel.org/r/Ya9eDiFCE2fO7K/S@xxxxxxxxxxxxxxxxxxxx/ [2]
Link: https://lore.kernel.org/r/20211207031449.100510-1-jefflexu@xxxxxxxxxxxxxxxxx/ [3]
---
The following changes since commit 0fcfb00b28c0b7884635dacf38e46d60bf3d4eb1:
Linux 5.16-rc4 (2021-12-05 14:08:22 -0800)
are available in the Git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/netfs-fixes-20211207
for you to fetch changes up to 3cfef1b612e15a0c2f5b1c9d3f3f31ad72d56fcd:
netfs: fix parameter of cleanup() (2021-12-07 15:47:09 +0000)
----------------------------------------------------------------
netfslib fixes
----------------------------------------------------------------
David Howells (1):
netfs: Fix lockdep warning from taking sb_writers whilst holding mmap_lock
Jeffle Xu (1):
netfs: fix parameter of cleanup()
fs/netfs/read_helper.c | 21 ++++++++-------------
1 file changed, 8 insertions(+), 13 deletions(-)
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