CephFS stores file data across multiple RADOS objects. An object is the atomic unit of storage, so the writeback code must clean only folios that belong to the same object with each OSD request.
CephFS also supports RAID0-style striping of file contents: if enabled, each object stores multiple unbroken "stripe units" covering different portions of the file; if disabled, a "stripe unit" is simply the whole object. The stripe unit is (usually) reported as the inode's block size.
Though the writeback logic could, in principle, lock all dirty folios belonging to the same object, its current design is to lock only a single stripe unit at a time. Ever since this code was first written, it has determined this size by checking the inode's block size. However, the relatively-new fscrypt support needed to reduce the block size for encrypted inodes to the crypto block size (see 'fixes' commit), which causes an unnecessarily high number of write operations (~1024x as many, with 4MiB objects) and correspondingly degraded performance.
Fix this (and clarify intent) by using i_layout.stripe_unit directly in ceph_define_write_size() so that encrypted inodes are written back with the same number of operations as if they were unencrypted.
Fixes: 94af0470924c ("ceph: add some fscrypt guardrails") Cc: stable@vger.kernel.org Signed-off-by: Sam Edwards CFSworks@gmail.com --- fs/ceph/addr.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index f2db05b51a3b..b97a6120d4b9 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -1000,7 +1000,8 @@ unsigned int ceph_define_write_size(struct address_space *mapping) { struct inode *inode = mapping->host; struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode); - unsigned int wsize = i_blocksize(inode); + struct ceph_inode_info *ci = ceph_inode(inode); + unsigned int wsize = ci->i_layout.stripe_unit;
if (fsc->mount_options->wsize < wsize) wsize = fsc->mount_options->wsize;