[PATCH 6.18 364/752] ceph: supply snapshot context in ceph_uninline_data()

Sasha Levin
2026-02-28T17:53:13Z

From: ethanwu <ethanwu@synology.com>

[ Upstream commit 305ff6b3a03c230d3c07b61457e961406d979693 ]

The ceph_uninline_data function was missing proper snapshot context
handling for its OSD write operations. Both CEPH_OSD_OP_CREATE and
CEPH_OSD_OP_WRITE requests were passing NULL instead of the appropriate
snapshot context, which could lead to unnecessary object clone.

Reproducer:
../src/vstart.sh --new -x --localhost --bluestore
// turn on cephfs inline data
./bin/ceph fs set a inline_data true --yes-i-really-really-mean-it
// allow fs_a client to take snapshot
./bin/ceph auth caps client.fs_a mds 'allow rwps fsname=a' mon 'allow r fsname=a' osd 'allow rw tag cephfs data=a'
// mount cephfs with fuse, since kernel cephfs doesn't support inline write
ceph-fuse --id fs_a -m 127.0.0.1:40318 --conf ceph.conf -d /mnt/mycephfs/
// bump snapshot seq
mkdir /mnt/mycephfs/.snap/snap1
echo "foo" > /mnt/mycephfs/test
// umount and mount it again using kernel cephfs client
umount /mnt/mycephfs
mount -t ceph fs_a@.a=/ /mnt/mycephfs/ -o conf=./ceph.conf
echo "bar" >> /mnt/mycephfs/test
./bin/rados listsnaps -p cephfs.a.data $(printf "%x\n" $(stat -c %i /mnt/mycephfs/test)).00000000

will see this object does unnecessary clone
1000000000a.00000000 (seq:2):
cloneid snaps size overlap
2 2 4 []
head - 8

but it's expected to see
10000000000.00000000 (seq:2):
cloneid snaps size overlap
head - 8

since there's no snapshot between these 2 writes

clone happened because the first osd request CEPH_OSD_OP_CREATE doesn't
pass snap context so object is created with snap seq 0, but later data
writeback is equipped with snapshot context.
snap.seq(1) > object snap seq(0), so osd does object clone.

This fix properly acquiring the snapshot context before performing
write operations.

Signed-off-by: ethanwu <ethanwu@synology.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Tested-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ceph/addr.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 322ed268f14aa..9faeaf1196c5c 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -2203,6 +2203,7 @@ int ceph_uninline_data(struct file *file)
struct ceph_osd_request *req = NULL;
struct ceph_cap_flush *prealloc_cf = NULL;
struct folio *folio = NULL;
+ struct ceph_snap_context *snapc = NULL;
u64 inline_version = CEPH_INLINE_NONE;
struct page *pages[1];
int err = 0;
@@ -2230,6 +2231,24 @@ int ceph_uninline_data(struct file *file)
if (inline_version == 1) /* initial version, no data */
goto out_uninline;

+ down_read(&fsc->mdsc->snap_rwsem);
+ spin_lock(&ci->i_ceph_lock);
+ if (__ceph_have_pending_cap_snap(ci)) {
+ struct ceph_cap_snap *capsnap =
+ list_last_entry(&ci->i_cap_snaps,
+ struct ceph_cap_snap,
+ ci_item);
+ snapc = ceph_get_snap_context(capsnap->context);
+ } else {
+ if (!ci->i_head_snapc) {
+ ci->i_head_snapc = ceph_get_snap_context(
+ ci->i_snap_realm->cached_context);
+ }
+ snapc = ceph_get_snap_context(ci->i_head_snapc);
+ }
+ spin_unlock(&ci->i_ceph_lock);
+ up_read(&fsc->mdsc->snap_rwsem);
+
folio = read_mapping_folio(inode->i_mapping, 0, file);
if (IS_ERR(folio)) {
err = PTR_ERR(folio);
@@ -2245,7 +2264,7 @@ int ceph_uninline_data(struct file *file)
req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
ceph_vino(inode), 0, &len, 0, 1,
CEPH_OSD_OP_CREATE, CEPH_OSD_FLAG_WRITE,
- NULL, 0, 0, false);
+ snapc, 0, 0, false);
if (IS_ERR(req)) {
err = PTR_ERR(req);
goto out_unlock;
@@ -2261,7 +2280,7 @@ int ceph_uninline_data(struct file *file)
req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
ceph_vino(inode), 0, &len, 1, 3,
CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
- NULL, ci->i_truncate_seq,
+ snapc, ci->i_truncate_seq,
ci->i_truncate_size, false);
if (IS_ERR(req)) {
err = PTR_ERR(req);
@@ -2324,6 +2343,7 @@ int ceph_uninline_data(struct file *file)
folio_put(folio);
}
out:
+ ceph_put_snap_context(snapc);
ceph_free_cap_flush(prealloc_cf);
doutc(cl, "%llx.%llx inline_version %llu = %d\n",
ceph_vinop(inode), inline_version, err);
--
2.51.0