From cac190c7674fea71620d754ffcdaaeed7c551dbc Mon Sep 17 00:00:00 2001 From: Sam Edwards Date: Sun, 25 Jan 2026 18:30:53 -0800 Subject: [PATCH] ceph: fix write storm on fscrypted files 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. This patch depends on the preceding commit ("ceph: do not propagate page array emplacement errors as batch errors") for correctness. While it applies cleanly on its own, applying it alone will introduce a regression. This dependency is only relevant for kernels where ce80b76dd327 ("ceph: introduce ceph_process_folio_batch() method") has been applied; stable kernels without that commit are unaffected. Cc: stable@vger.kernel.org Fixes: 94af0470924c ("ceph: add some fscrypt guardrails") Signed-off-by: Sam Edwards Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov --- 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 3cfe3df6e6a2..c6c853748942 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; -- 2.47.3