| Message ID | 20241213135013.2964079-1-dhowells@redhat.com |
|---|---|
| Headers | show |
| Series | netfs, ceph, nfs, cachefiles: Miscellaneous fixes/changes | expand |
[Adding Paul McKenney as he's the expert.] Akira Yokosawa <akiyks@gmail.com> wrote: > David Howells wrote: > > Use clear_and_wake_up_bit() rather than something like: > > > > clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags); > > wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS); > > > > as there needs to be a barrier inserted between which is present in > > clear_and_wake_up_bit(). > > If I am reading the kernel-doc comment of clear_bit_unlock() [1, 2]: > > This operation is atomic and provides release barrier semantics. > > correctly, there already seems to be a barrier which should be > good enough. > > [1]: https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.clear_bit_unlock > [2]: include/asm-generic/bitops/instrumented-lock.h > > > > > Fixes: 288ace2f57c9 ("netfs: New writeback implementation") > > Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") > > So I'm not sure this fixes anything. > > What am I missing? We may need two barriers. You have three things to synchronise: (1) The stuff you did before unlocking. (2) The lock bit. (3) The task state. clear_bit_unlock() interposes a release barrier between (1) and (2). Neither clear_bit_unlock() nor wake_up_bit(), however, necessarily interpose a barrier between (2) and (3). I'm not sure it entirely matters, but it seems that since we have a function that combines the two, we should probably use it - though, granted, it might not actually be a fix. David
Hi Christian, Here are some miscellaneous fixes and changes for netfslib and the ceph and nfs filesystems: (1) Ignore silly-rename files from afs and nfs when building the header archive in a kernel build. (2) netfs: Fix the way read result collection applies results to folios when each folio is being read by multiple subrequests and the results come out of order. (3) netfs: Fix ENOMEM handling in buffered reads. (4) nfs: Fix an oops in nfs_netfs_init_request() when copying to the cache. (5) cachefiles: Parse the "secctx" command immediately to get the correct error rather than leaving it to the "bind" command. (6) netfs: Remove a redundant smp_rmb(). This isn't a bug per se and could be deferred. (7) netfs: Fix missing barriers by using clear_and_wake_up_bit(). (8) netfs: Work around recursion in read retry by failing and abandoning the retried subrequest if no I/O is performed. [!] NOTE: This only works around the recursion problem if the recursion keeps returning no data. If the server manages, say, to repeatedly return a single byte of data faster than the retry algorithm can complete, it will still recurse and the stack overrun may still occur. Actually fixing this requires quite an intrusive change which will hopefully make the next merge window. (9) netfs: Fix the clearance of a folio_queue when unlocking the page if we're going to want to subsequently send the queue for copying to the cache (if, for example, we're using ceph). (10) netfs: Fix the lack of cancellation of copy-to-cache when the cache for a file is temporarily disabled (for example when a DIO write is done to the file). This patch and (9) fix hangs with ceph. With these patches, I can run xfstest -g quick to completion on ceph with a local cache. The patches can also be found here with a bonus cifs patch: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-fixes Thanks, David David Howells (8): kheaders: Ignore silly-rename files netfs: Fix non-contiguous donation between completed reads netfs: Fix enomem handling in buffered reads nfs: Fix oops in nfs_netfs_init_request() when copying to cache netfs: Fix missing barriers by using clear_and_wake_up_bit() netfs: Work around recursion by abandoning retry if nothing read netfs: Fix ceph copy to cache on write-begin netfs: Fix the (non-)cancellation of copy when cache is temporarily disabled Max Kellermann (1): cachefiles: Parse the "secctx" immediately Zilin Guan (1): netfs: Remove redundant use of smp_rmb() fs/9p/vfs_addr.c | 6 +++++- fs/afs/write.c | 5 ++++- fs/cachefiles/daemon.c | 14 +++++++------- fs/cachefiles/internal.h | 3 ++- fs/cachefiles/security.c | 6 +++--- fs/netfs/buffered_read.c | 28 ++++++++++++++++------------ fs/netfs/direct_write.c | 1 - fs/netfs/read_collect.c | 33 +++++++++++++++++++-------------- fs/netfs/read_pgpriv2.c | 4 ++++ fs/netfs/read_retry.c | 6 ++++-- fs/netfs/write_collect.c | 14 +++++--------- fs/netfs/write_issue.c | 2 ++ fs/nfs/fscache.c | 9 ++++++++- fs/smb/client/cifssmb.c | 13 +++++++++---- fs/smb/client/smb2pdu.c | 9 ++++++--- include/linux/netfs.h | 6 +++--- kernel/gen_kheaders.sh | 1 + 17 files changed, 98 insertions(+), 62 deletions(-)