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snapshot: keep COW writable for read-only volumes

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When snapshot is created in read-only mode with 'lvcreate -s -pr...',
lvm2 still needs to be able to write to layered -cow volume
to store metadata and exceptions blocks.

TODO: in some case we might be able to do full tree with read-only
volume but this probably needs futher validation:
1. checking snapshot header already exist
2. origin & snapshot are both in read-only mode.
This commit is contained in:
Zdenek Kabelac 2018-03-08 10:27:04 +01:00
parent 15b6793528
commit a6fdb9d9d7
4 changed files with 8 additions and 4 deletions
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1
WHATS_NEW
View File

@ -1,5 +1,6 @@
Version 2.02.178 -
=====================================
Ensure COW device is writable even for read-only thick snapshots.
Support activation of component LVs in read-only mode.
Extend internal library to recognize and work with component LV.
Skip duplicate check for active LV when prompting for its removal.

2
lib/activate/activate.c
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@ -2694,7 +2694,7 @@ static int _lv_activate(struct cmd_context *cmd, const char *lvid_s,
* Nothing to do?
*/
if (info.exists && !info.suspended && info.live_table &&
(info.read_only == read_only_lv(lv, laopts))) {
(info.read_only == read_only_lv(lv, laopts, NULL))) {
r = 1;
log_debug_activation("LV %s is already active.", display_lvname(lv));
goto out;

7
lib/activate/dev_manager.c
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@ -75,8 +75,11 @@ struct lv_layer {
int visible_component;
};
int read_only_lv(const struct logical_volume *lv, const struct lv_activate_opts *laopts)
int read_only_lv(const struct logical_volume *lv, const struct lv_activate_opts *laopts, const char *layer)
{
if (layer && lv_is_cow(lv))
return 0; /* Keep snapshot's COW volume writable */
return (laopts->read_only || !(lv->status & LVM_WRITE));
}
@ -2824,7 +2827,7 @@ static int _add_new_lv_to_dtree(struct dev_manager *dm, struct dm_tree *dtree,
if (!(dnode = dm_tree_add_new_dev_with_udev_flags(dtree, name, dlid,
layer ? UINT32_C(0) : (uint32_t) lv->major,
layer ? UINT32_C(0) : (uint32_t) lv->minor,
read_only_lv(lv, laopts),
read_only_lv(lv, laopts, layer),
((lv->vg->status & PRECOMMITTED) | laopts->revert) ? 1 : 0,
lvlayer,
_get_udev_flags(dm, lv, layer, laopts->noscan, laopts->temporary,

2
lib/activate/dev_manager.h
View File

@ -27,7 +27,7 @@ struct dm_info;
struct device;
struct lv_seg_status;
int read_only_lv(const struct logical_volume *lv, const struct lv_activate_opts *laopts);
int read_only_lv(const struct logical_volume *lv, const struct lv_activate_opts *laopts, const char *layer);
/*
* Constructor and destructor.