From https://pulpito.ceph.com/vshankar-2022-06-10_05:38:08-fs-wip-vshankar-testing1-20220607-104134-testing-default-smithi/6872838/remote/smithi120/log/ceph-mds.a.log.gz:
For the normal test case, which succeeded, we can see that when lookup the snapshot file #0x100000013fe//s/a, the size is s=66266488:
-8420> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 7 mds.1.server dispatch_client_request client_request(client.4785:113102 lookup #0x100000013fe//s/a 2022-06-10T06:20:49.731528+0000 caller_uid=1000, caller_gid=1264{6,36,1000,1264,}) v6
-8419> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.server rdlock_path_pin_ref request(client.4785:113102 nref=2 cr=0x55b94fb58000) #0x100000013fe//s/a
-8418> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 7 mds.1.cache traverse: opening base ino 0x100000013fe snap head
-8417> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 12 mds.1.cache traverse: path seg depth 0 '' snapid head
-8416> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.cache traverse: snapdir
-8415> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 12 mds.1.cache traverse: path seg depth 1 's' snapid snapdir
-8414> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.cache.snaprealm(0x100000013fe seq 596 0x55b94de61c00) resolve_snapname 's' in [0,head]
-8413> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 15 mds.1.cache.snaprealm(0x100000013fe seq 596 0x55b94de61c00) ? snap(254 0x100000013fe 's' 2022-06-10T06:20:49.665051+0000)
-8412> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.cache traverse: snap s -> 254
-8411> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 12 mds.1.cache traverse: path seg depth 2 'a' snapid 254
-8410> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 20 mds.1.cache.dir(0x100000013fe) lookup (a, '254')
-8409> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 20 mds.1.cache.dir(0x100000013fe) hit -> (a,254)
-8408> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.cache path_traverse finish on snapid 254
-8407> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.server ref is [inode 0x200000007a2 [254,254] /client.0/tmp/a auth v210 s=66266488 n(v0 rc2022-06-10T06:20:49.653709+0000 b66266488 1=1+0) (iversion lock) | request=0 dirty=1 0x55b94e99fb80]
-8406> 2022-06-10T06:20:49.731+0000 7fa1e25f6700 10 mds.1.cache.ino(0x200000007a2) auth_pin by 0x55b94e82f800 on [inode 0x200000007a2 [254,254] /client.0/tmp/a auth v210 ap=1 s=66266488 n(v0 rc2022-06-10T06:20:49.653709+0000 b66266488 1=1+0) (iversion lock) | request=0 dirty=1 authpin=1 0x55b94e99fb80] now 1
While for the failure one the size is s=65798144:
-4299> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 7 mds.1.server dispatch_client_request client_request(client.4785:113134 lookup #0x100000013fe//s/a 2022-06-10T06:20:52.398271+0000 caller_uid=1000, caller_gid=1264{6,36,1000,1264,}) v6
-4298> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.server rdlock_path_pin_ref request(client.4785:113134 nref=2 cr=0x55b94f6fb600) #0x100000013fe//s/a
-4297> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 7 mds.1.cache traverse: opening base ino 0x100000013fe snap head
-4296> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 12 mds.1.cache traverse: path seg depth 0 '' snapid head
-4295> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.cache traverse: snapdir
-4294> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 12 mds.1.cache traverse: path seg depth 1 's' snapid snapdir
-4293> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.cache.snaprealm(0x100000013fe seq 600 0x55b94de61c00) resolve_snapname 's' in [0,head]
-4292> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 15 mds.1.cache.snaprealm(0x100000013fe seq 600 0x55b94de61c00) ? snap(258 0x100000013fe 's' 2022-06-10T06:20:52.220723+0000)
-4291> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.cache traverse: snap s -> 258
-4290> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 12 mds.1.cache traverse: path seg depth 2 'a' snapid 258
-4289> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 20 mds.1.cache.dir(0x100000013fe) lookup (a, '258')
-4288> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 20 mds.1.cache.dir(0x100000013fe) hit -> (a,258)
-4287> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.cache path_traverse finish on snapid 258
-4286> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.server ref is [inode 0x200000007a4 [258,258] /client.0/tmp/a auth v256 s=65798144 n(v0 rc2022-06-10T06:20:52.181418+0000 b65798144 1=1+0) (iversion lock) | ptrwaiter=0 request=0 lock=0 dirty=1 authpin=0 0x55b94f402680]
-4285> 2022-06-10T06:20:52.397+0000 7fa1e25f6700 10 mds.1.cache.ino(0x200000007a4) auth_pin by 0x55b94e850c00 on [inode 0x200000007a4 [258,258] /client.0/tmp/a auth v256 ap=1 s=65798144 n(v0 rc2022-06-10T06:20:52.181418+0000 b65798144 1=1+0) (iversion lock) | ptrwaiter=0 request=0 lock=0 dirty=1 authpin=1 0x55b94f402680] now 1
Downloaded the file and list it, we can see the real size is 66266488:
# wget -q http://download.ceph.com/qa/linux-2.6.33.tar.bz2
# ll linux-2.6.33.tar.bz2
-rw-r--r--. 1 root root 66266488 Feb 25 2010 linux-2.6.33.tar.bz2