diff options
| author | David Howells <dhowells@redhat.com> | 2024-10-16 17:28:33 +0100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-10-17 15:33:42 +0200 |
| commit | d6a77668a708f0b5ca6713b39c178c9d9563c35b (patch) | |
| tree | e52f1914eb0aa35b4ed7266988cb6b9511d0b5ab /fs | |
| parent | 6ed469df0bfbef3e4b44fca954a781919db9f7ab (diff) | |
netfs: Downgrade i_rwsem for a buffered write
In the I/O locking code borrowed from NFS into netfslib, i_rwsem is held
locked across a buffered write - but this causes a performance regression
in cifs as it excludes buffered reads for the duration (cifs didn't use any
locking for buffered reads).
Mitigate this somewhat by downgrading the i_rwsem to a read lock across the
buffered write. This at least allows parallel reads to occur whilst
excluding other writes, DIO, truncate and setattr.
Note that this shouldn't be a problem for a buffered write as a read
through an mmap can circumvent i_rwsem anyway.
Also note that we might want to make this change in NFS also.
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/1317958.1729096113@warthog.procyon.org.uk
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Trond Myklebust <trondmy@kernel.org>
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/netfs/locking.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/netfs/locking.c b/fs/netfs/locking.c index 21eab56ee2f9..2249ecd09d0a 100644 --- a/fs/netfs/locking.c +++ b/fs/netfs/locking.c @@ -109,6 +109,7 @@ int netfs_start_io_write(struct inode *inode) up_write(&inode->i_rwsem); return -ERESTARTSYS; } + downgrade_write(&inode->i_rwsem); return 0; } EXPORT_SYMBOL(netfs_start_io_write); @@ -123,7 +124,7 @@ EXPORT_SYMBOL(netfs_start_io_write); void netfs_end_io_write(struct inode *inode) __releases(inode->i_rwsem) { - up_write(&inode->i_rwsem); + up_read(&inode->i_rwsem); } EXPORT_SYMBOL(netfs_end_io_write); |