LU-14217 osd-zfs: allow SEEK_HOLE/DATA only with sync

[fs/lustre-release.git] / lustre / osd-zfs / osd_io.c

diff --git a/lustre/osd-zfs/osd_io.c b/lustre/osd-zfs/osd_io.c
index 8605196..f42eb5f 100644 (file)
--- a/lustre/osd-zfs/osd_io.c
+++ b/lustre/osd-zfs/osd_io.c
@@ -1180,6 +1180,7 @@ static loff_t osd_lseek(const struct lu_env *env, struct dt_object *dt,
                        loff_t offset, int whence)
 {
        struct osd_object *obj = osd_dt_obj(dt);
+       struct osd_device *osd = osd_obj2dev(obj);
        uint64_t size = obj->oo_attr.la_size;
        uint64_t result = offset;
        int rc;
@@ -1197,17 +1198,40 @@ static loff_t osd_lseek(const struct lu_env *env, struct dt_object *dt,
        if (offset >= size)
                RETURN(hole ? offset : -ENXIO);
 
-       rc = osd_dmu_offset_next(osd_obj2dev(obj)->od_os,
-                                obj->oo_dn->dn_object, hole, &result);
+       /* Currently ZFS reports no valid DATA offset if object has dirty data
+        * and we cannot just switch to generic way with reporting DATA on all
+        * file offsets and HOLE beyond end of file, because we may get HOLE
+        * reported correctly at some offset inside file then DATA will find
+        * dirty state and be reported also at that offset by generic approach.
+        * This is because for HOLE report ZFS doesn't check dirty state but
+        * does for DATA.
+        * The only way to get reliable results is to call txg_wait_synced()
+        * when ZFS reports EBUSY result and repeat lseek call and that is
+        * controlled via od_sync_on_lseek option.
+        */
+       if (!osd->od_sync_on_lseek)
+               result = hole ? size : offset;
+
+again:
+       rc = osd_dmu_offset_next(osd->od_os, obj->oo_dn->dn_object, hole,
+                                &result);
+       /* dirty inode, lseek result is unreliable without sync */
+       if (rc == EBUSY) {
+               txg_wait_synced(dmu_objset_pool(osd->od_os), 0ULL);
+               goto again;
+       }
+
        if (rc == ESRCH)
                RETURN(-ENXIO);
 
-       /* file was dirty, so fall back to using generic logic:
-        * For HOLE return file size, for DATA the result is set
-        * already to the 'offset' parameter value.
+       /* ZFS is not exported all needed function, so fall back to the
+        * generic logic: for HOLE return file size, for DATA return
+        * the current offset
         */
-       if (rc == EBUSY && hole)
-               result = size;
+       if (rc == EOPNOTSUPP)
+               result = hole ? size : offset;
+       else if (rc)
+               return -rc;
 
        /* dmu_offset_next() only works on whole blocks so may return SEEK_HOLE
         * result as end of the last block instead of logical EOF which we need