- 根目录:
- fs
- ceph
- snap.c
#include <linux/ceph/ceph_debug.h>
#include <linux/sort.h>
#include <linux/slab.h>
#include "super.h"
#include "mds_client.h"
#include <linux/ceph/decode.h>
/*
* Snapshots in ceph are driven in large part by cooperation from the
* client. In contrast to local file systems or file servers that
* implement snapshots at a single point in the system, ceph's
* distributed access to storage requires clients to help decide
* whether a write logically occurs before or after a recently created
* snapshot.
*
* This provides a perfect instantanous client-wide snapshot. Between
* clients, however, snapshots may appear to be applied at slightly
* different points in time, depending on delays in delivering the
* snapshot notification.
*
* Snapshots are _not_ file system-wide. Instead, each snapshot
* applies to the subdirectory nested beneath some directory. This
* effectively divides the hierarchy into multiple "realms," where all
* of the files contained by each realm share the same set of
* snapshots. An individual realm's snap set contains snapshots
* explicitly created on that realm, as well as any snaps in its
* parent's snap set _after_ the point at which the parent became it's
* parent (due to, say, a rename). Similarly, snaps from prior parents
* during the time intervals during which they were the parent are included.
*
* The client is spared most of this detail, fortunately... it must only
* maintains a hierarchy of realms reflecting the current parent/child
* realm relationship, and for each realm has an explicit list of snaps
* inherited from prior parents.
*
* A snap_realm struct is maintained for realms containing every inode
* with an open cap in the system. (The needed snap realm information is
* provided by the MDS whenever a cap is issued, i.e., on open.) A 'seq'
* version number is used to ensure that as realm parameters change (new
* snapshot, new parent, etc.) the client's realm hierarchy is updated.
*
* The realm hierarchy drives the generation of a 'snap context' for each
* realm, which simply lists the resulting set of snaps for the realm. This
* is attached to any writes sent to OSDs.
*/
/*
* Unfortunately error handling is a bit mixed here. If we get a snap
* update, but don't have enough memory to update our realm hierarchy,
* it's not clear what we can do about it (besides complaining to the
* console).
*/
/*
* increase ref count for the realm
*
* caller must hold snap_rwsem for write.
*/
void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm)
{
dout("get_realm %p %d -> %d\n", realm,
atomic_read(&realm->nref), atomic_read(&realm->nref)+1);
/*
* since we _only_ increment realm refs or empty the empty
* list with snap_rwsem held, adjusting the empty list here is
* safe. we do need to protect against concurrent empty list
* additions, however.
*/
if (atomic_inc_return(&realm->nref) == 1) {
spin_lock(&mdsc->snap_empty_lock);
list_del_init(&realm->empty_item);
spin_unlock(&mdsc->snap_empty_lock);
}
}
static void __insert_snap_realm(struct rb_root *root,
struct ceph_snap_realm *new)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct ceph_snap_realm *r = NULL;
while (*p) {
parent = *p;
r = rb_entry(parent, struct ceph_snap_realm, node);
if (new->ino < r->ino)
p = &(*p)->rb_left;
else if (new->ino > r->ino)
p = &(*p)->rb_right;
else
BUG();
}
rb_link_node(&new->node, parent, p);
rb_insert_color(&new->node, root);
}
/*
* create and get the realm rooted at @ino and bump its ref count.
*
* caller must hold snap_rwsem for write.
*/
static struct ceph_snap_realm *ceph_create_snap_realm(
struct ceph_mds_client *mdsc,
u64 ino)
{
struct ceph_snap_realm *realm;
realm = kzalloc(sizeof(*realm), GFP_NOFS);
if (!realm)
return ERR_PTR(-ENOMEM);
atomic_set(&realm->nref, 1); /* for caller */
realm->ino = ino;
INIT_LIST_HEAD(&realm->children);
INIT_LIST_HEAD(&realm->child_item);
INIT_LIST_HEAD(&realm->empty_item);
INIT_LIST_HEAD(&realm->dirty_item);
INIT_LIST_HEAD(&realm->inodes_with_caps);
spin_lock_init(&realm->inodes_with_caps_lock);
__insert_snap_realm(&mdsc->snap_realms, realm);
dout("create_snap_realm %llx %p\n", realm->ino, realm);
return realm;
}
/*
* lookup the realm rooted at @ino.
*
* caller must hold snap_rwsem for write.
*/
static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
u64 ino)
{
struct rb_node *n = mdsc->snap_realms.rb_node;
struct ceph_snap_realm *r;
while (n) {
r = rb_entry(n, struct ceph_snap_realm, node);
if (ino < r->ino)
n = n->rb_left;
else if (ino > r->ino)
n = n->rb_right;
else {
dout("lookup_snap_realm %llx %p\n", r->ino, r);
return r;
}
}
return NULL;
}
struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
u64 ino)
{
struct ceph_snap_realm *r;
r = __lookup_snap_realm(mdsc, ino);
if (r)
ceph_get_snap_realm(mdsc, r);
return r;
}
static void __put_snap_realm(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm);
/*
* called with snap_rwsem (write)
*/
static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm)
{
dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);
rb_erase(&realm->node, &mdsc->snap_realms);
if (realm->parent) {
list_del_init(&realm->child_item);
__put_snap_realm(mdsc, realm->parent);
}
kfree(realm->prior_parent_snaps);
kfree(realm->snaps);
ceph_put_snap_context(realm->cached_context);
kfree(realm);
}
/*
* caller holds snap_rwsem (write)
*/
static void __put_snap_realm(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm)
{
dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
if (atomic_dec_and_test(&realm->nref))
__destroy_snap_realm(mdsc, realm);
}
/*
* caller needn't hold any locks
*/
void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm)
{
dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
if (!atomic_dec_and_test(&realm->nref))
return;
if (down_write_trylock(&mdsc->snap_rwsem)) {
__destroy_snap_realm(mdsc, realm);
up_write(&mdsc->snap_rwsem);
} else {
spin_lock(&mdsc->snap_empty_lock);
list_add(&realm->empty_item, &mdsc->snap_empty);
spin_unlock(&mdsc->snap_empty_lock);
}
}
/*
* Clean up any realms whose ref counts have dropped to zero. Note
* that this does not include realms who were created but not yet
* used.
*
* Called under snap_rwsem (write)
*/
static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
{
struct ceph_snap_realm *realm;
spin_lock(&mdsc->snap_empty_lock);
while (!list_empty(&mdsc->snap_empty)) {
realm = list_first_entry(&mdsc->snap_empty,
struct ceph_snap_realm, empty_item);
list_del(&realm->empty_item);
spin_unlock(&mdsc->snap_empty_lock);
__destroy_snap_realm(mdsc, realm);
spin_lock(&mdsc->snap_empty_lock);
}
spin_unlock(&mdsc->snap_empty_lock);
}
void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
{
down_write(&mdsc->snap_rwsem);
__cleanup_empty_realms(mdsc);
up_write(&mdsc->snap_rwsem);
}
/*
* adjust the parent realm of a given @realm. adjust child list, and parent
* pointers, and ref counts appropriately.
*
* return true if parent was changed, 0 if unchanged, <0 on error.
*
* caller must hold snap_rwsem for write.
*/
static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm,
u64 parentino)
{
struct ceph_snap_realm *parent;
if (realm->parent_ino == parentino)
return 0;
parent = ceph_lookup_snap_realm(mdsc, parentino);
if (!parent) {
parent = ceph_create_snap_realm(mdsc, parentino);
if (IS_ERR(parent))
return PTR_ERR(parent);
}
dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
realm->ino, realm, realm->parent_ino, realm->parent,
parentino, parent);
if (realm->parent) {
list_del_init(&realm->child_item);
ceph_put_snap_realm(mdsc, realm->parent);
}
realm->parent_ino = parentino;
realm->parent = parent;
list_add(&realm->child_item, &parent->children);
return 1;
}
static int cmpu64_rev(const void *a, const void *b)
{
if (*(u64 *)a < *(u64 *)b)
return 1;
if (*(u64 *)a > *(u64 *)b)
return -1;
return 0;
}
struct ceph_snap_context *ceph_empty_snapc;
/*
* build the snap context for a given realm.
*/
static int build_snap_context(struct ceph_snap_realm *realm)
{
struct ceph_snap_realm *parent = realm->parent;
struct ceph_snap_context *snapc;
int err = 0;
u32 num = realm->num_prior_parent_snaps + realm->num_snaps;
/*
* build parent context, if it hasn't been built.
* conservatively estimate that all parent snaps might be
* included by us.
*/
if (parent) {
if (!parent->cached_context) {
err = build_snap_context(parent);
if (err)
goto fail;
}
num += parent->cached_context->num_snaps;
}
/* do i actually need to update? not if my context seq
matches realm seq, and my parents' does to. (this works
because we rebuild_snap_realms() works _downward_ in
hierarchy after each update.) */
if (realm->cached_context &&
realm->cached_context->seq == realm->seq &&
(!parent ||
realm->cached_context->seq >= parent->cached_context->seq)) {
dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
" (unchanged)\n",
realm->ino, realm, realm->cached_context,
realm->cached_context->seq,
(unsigned int) realm->cached_context->num_snaps);
return 0;
}
/* alloc new snap context */
err = -ENOMEM;
if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
goto fail;
snapc = ceph_create_snap_context(num, GFP_NOFS);
if (!snapc)
goto fail;
/* build (reverse sorted) snap vector */
num = 0;
snapc->seq = realm->seq;
if (parent) {
u32 i;
/* include any of parent's snaps occurring _after_ my
parent became my parent */
for (i = 0; i < parent->cached_context->num_snaps; i++)
if (parent->cached_context->snaps[i] >=
realm->parent_since)
snapc->snaps[num++] =
parent->cached_context->snaps[i];
if (parent->cached_context->seq > snapc->seq)
snapc->seq = parent->cached_context->seq;
}
memcpy(snapc->snaps + num, realm->snaps,
sizeof(u64)*realm->num_snaps);
num += realm->num_snaps;
memcpy(snapc->snaps + num, realm->prior_parent_snaps,
sizeof(u64)*realm->num_prior_parent_snaps);
num += realm->num_prior_parent_snaps;
sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
snapc->num_snaps = num;
dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
realm->ino, realm, snapc, snapc->seq,
(unsigned int) snapc->num_snaps);
ceph_put_snap_context(realm->cached_context);
realm->cached_context = snapc;
return 0;
fail:
/*
* if we fail, clear old (incorrect) cached_context... hopefully
* we'll have better luck building it later
*/
if (realm->cached_context) {
ceph_put_snap_context(realm->cached_context);
realm->cached_context = NULL;
}
pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
realm, err);
return err;
}
/*
* rebuild snap context for the given realm and all of its children.
*/
static void rebuild_snap_realms(struct ceph_snap_realm *realm)
{
struct ceph_snap_realm *child;
dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
build_snap_context(realm);
list_for_each_entry(child, &realm->children, child_item)
rebuild_snap_realms(child);
}
/*
* helper to allocate and decode an array of snapids. free prior
* instance, if any.
*/
static int dup_array(u64 **dst, __le64 *src, u32 num)
{
u32 i;
kfree(*dst);
if (num) {
*dst = kcalloc(num, sizeof(u64), GFP_NOFS);
if (!*dst)
return -ENOMEM;
for (i = 0; i < num; i++)
(*dst)[i] = get_unaligned_le64(src + i);
} else {
*dst = NULL;
}
return 0;
}
static bool has_new_snaps(struct ceph_snap_context *o,
struct ceph_snap_context *n)
{
if (n->num_snaps == 0)
return false;
/* snaps are in descending order */
return n->snaps[0] > o->seq;
}
/*
* When a snapshot is applied, the size/mtime inode metadata is queued
* in a ceph_cap_snap (one for each snapshot) until writeback
* completes and the metadata can be flushed back to the MDS.
*
* However, if a (sync) write is currently in-progress when we apply
* the snapshot, we have to wait until the write succeeds or fails
* (and a final size/mtime is known). In this case the
* cap_snap->writing = 1, and is said to be "pending." When the write
* finishes, we __ceph_finish_cap_snap().
*
* Caller must hold snap_rwsem for read (i.e., the realm topology won't
* change).
*/
void ceph_queue_cap_snap(struct ceph_inode_info *ci)
{
struct inode *inode = &ci->vfs_inode;
struct ceph_cap_snap *capsnap;
struct ceph_snap_context *old_snapc, *new_snapc;
int used, dirty;
capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
if (!capsnap) {
pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
return;
}
spin_lock(&ci->i_ceph_lock);
used = __ceph_caps_used(ci);
dirty = __ceph_caps_dirty(ci);
old_snapc = ci->i_head_snapc;
new_snapc = ci->i_snap_realm->cached_context;
/*
* If there is a write in progress, treat that as a dirty Fw,
* even though it hasn't completed yet; by the time we finish
* up this capsnap it will be.
*/
if (used & CEPH_CAP_FILE_WR)
dirty |= CEPH_CAP_FILE_WR;
if (__ceph_have_pending_cap_snap(ci)) {
/* there is no point in queuing multiple "pending" cap_snaps,
as no new writes are allowed to start when pending, so any
writes in progress now were started before the previous
cap_snap. lucky us. */
dout("queue_cap_snap %p already pending\n", inode);
goto update_snapc;
}
if (ci->i_wrbuffer_ref_head == 0 &&
!(dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))) {
dout("queue_cap_snap %p nothing dirty|writing\n", inode);
goto update_snapc;
}
BUG_ON(!old_snapc);
/*
* There is no need to send FLUSHSNAP message to MDS if there is
* no new snapshot. But when there is dirty pages or on-going
* writes, we still need to create cap_snap. cap_snap is needed
* by the write path and page writeback path.
*
* also see ceph_try_drop_cap_snap()
*/
if (has_new_snaps(old_snapc, new_snapc)) {
if (dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))
capsnap->need_flush = true;
} else {
if (!(used & CEPH_CAP_FILE_WR) &&
ci->i_wrbuffer_ref_head == 0) {
dout("queue_cap_snap %p "
"no new_snap|dirty_page|writing\n", inode);
goto update_snapc;
}
}
dout("queue_cap_snap %p cap_snap %p queuing under %p %s %s\n",
inode, capsnap, old_snapc, ceph_cap_string(dirty),
capsnap->need_flush ? "" : "no_flush");
ihold(inode);
atomic_set(&capsnap->nref, 1);
capsnap->ci = ci;
INIT_LIST_HEAD(&capsnap->ci_item);
INIT_LIST_HEAD(&capsnap->flushing_item);
capsnap->follows = old_snapc->seq;
capsnap->issued = __ceph_caps_issued(ci, NULL);
capsnap->dirty = dirty;
capsnap->mode = inode->i_mode;
capsnap->uid = inode->i_uid;
capsnap->gid = inode->i_gid;
if (dirty & CEPH_CAP_XATTR_EXCL) {
__ceph_build_xattrs_blob(ci);
capsnap->xattr_blob =
ceph_buffer_get(ci->i_xattrs.blob);
capsnap->xattr_version = ci->i_xattrs.version;
} else {
capsnap->xattr_blob = NULL;
capsnap->xattr_version = 0;
}
capsnap->inline_data = ci->i_inline_version != CEPH_INLINE_NONE;
/* dirty page count moved from _head to this cap_snap;
all subsequent writes page dirties occur _after_ this
snapshot. */
capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
ci->i_wrbuffer_ref_head = 0;
capsnap->context = old_snapc;
list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
old_snapc = NULL;
if (used & CEPH_CAP_FILE_WR) {
dout("queue_cap_snap %p cap_snap %p snapc %p"
" seq %llu used WR, now pending\n", inode,
capsnap, old_snapc, old_snapc->seq);
capsnap->writing = 1;
} else {
/* note mtime, size NOW. */
__ceph_finish_cap_snap(ci, capsnap);
}
capsnap = NULL;
update_snapc:
if (ci->i_head_snapc) {
ci->i_head_snapc = ceph_get_snap_context(new_snapc);
dout(" new snapc is %p\n", new_snapc);
}
spin_unlock(&ci->i_ceph_lock);
kfree(capsnap);
ceph_put_snap_context(old_snapc);
}
/*
* Finalize the size, mtime for a cap_snap.. that is, settle on final values
* to be used for the snapshot, to be flushed back to the mds.
*
* If capsnap can now be flushed, add to snap_flush list, and return 1.
*
* Caller must hold i_ceph_lock.
*/
int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
struct ceph_cap_snap *capsnap)
{
struct inode *inode = &ci->vfs_inode;
struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
BUG_ON(capsnap->writing);
capsnap->size = inode->i_size;
capsnap->mtime = inode->i_mtime;
capsnap->atime = inode->i_atime;
capsnap->ctime = inode->i_ctime;
capsnap->time_warp_seq = ci->i_time_warp_seq;
if (capsnap->dirty_pages) {
dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
"still has %d dirty pages\n", inode, capsnap,
capsnap->context, capsnap->context->seq,
ceph_cap_string(capsnap->dirty), capsnap->size,
capsnap->dirty_pages);
return 0;
}
dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
inode, capsnap, capsnap->context,
capsnap->context->seq, ceph_cap_string(capsnap->dirty),
capsnap->size);
spin_lock(&mdsc->snap_flush_lock);
list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
spin_unlock(&mdsc->snap_flush_lock);
return 1; /* caller may want to ceph_flush_snaps */
}
/*
* Queue cap_snaps for snap writeback for this realm and its children.
* Called under snap_rwsem, so realm topology won't change.
*/
static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
{
struct ceph_inode_info *ci;
struct inode *lastinode = NULL;
struct ceph_snap_realm *child;
dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);
spin_lock(&realm->inodes_with_caps_lock);
list_for_each_entry(ci, &realm->inodes_with_caps,
i_snap_realm_item) {
struct inode *inode = igrab(&ci->vfs_inode);
if (!inode)
continue;
spin_unlock(&realm->inodes_with_caps_lock);
iput(lastinode);
lastinode = inode;
ceph_queue_cap_snap(ci);
spin_lock(&realm->inodes_with_caps_lock);
}
spin_unlock(&realm->inodes_with_caps_lock);
iput(lastinode);
list_for_each_entry(child, &realm->children, child_item) {
dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
realm, realm->ino, child, child->ino);
list_del_init(&child->dirty_item);
list_add(&child->dirty_item, &realm->dirty_item);
}
list_del_init(&realm->dirty_item);
dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
}
/*
* Parse and apply a snapblob "snap trace" from the MDS. This specifies
* the snap realm parameters from a given realm and all of its ancestors,
* up to the root.
*
* Caller must hold snap_rwsem for write.
*/
int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
void *p, void *e, bool deletion,
struct ceph_snap_realm **realm_ret)
{
struct ceph_mds_snap_realm *ri; /* encoded */
__le64 *snaps; /* encoded */
__le64 *prior_parent_snaps; /* encoded */
struct ceph_snap_realm *realm = NULL;
struct ceph_snap_realm *first_realm = NULL;
int invalidate = 0;
int err = -ENOMEM;
LIST_HEAD(dirty_realms);
dout("update_snap_trace deletion=%d\n", deletion);
more:
ceph_decode_need(&p, e, sizeof(*ri), bad);
ri = p;
p += sizeof(*ri);
ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) +
le32_to_cpu(ri->num_prior_parent_snaps)), bad);
snaps = p;
p += sizeof(u64) * le32_to_cpu(ri->num_snaps);
prior_parent_snaps = p;
p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps);
realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino));
if (!realm) {
realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino));
if (IS_ERR(realm)) {
err = PTR_ERR(realm);
goto fail;
}
}
/* ensure the parent is correct */
err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
if (err < 0)
goto fail;
invalidate += err;
if (le64_to_cpu(ri->seq) > realm->seq) {
dout("update_snap_trace updating %llx %p %lld -> %lld\n",
realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
/* update realm parameters, snap lists */
realm->seq = le64_to_cpu(ri->seq);
realm->created = le64_to_cpu(ri->created);
realm->parent_since = le64_to_cpu(ri->parent_since);
realm->num_snaps = le32_to_cpu(ri->num_snaps);
err = dup_array(&realm->snaps, snaps, realm->num_snaps);
if (err < 0)
goto fail;
realm->num_prior_parent_snaps =
le32_to_cpu(ri->num_prior_parent_snaps);
err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps,
realm->num_prior_parent_snaps);
if (err < 0)
goto fail;
/* queue realm for cap_snap creation */
list_add(&realm->dirty_item, &dirty_realms);
if (realm->seq > mdsc->last_snap_seq)
mdsc->last_snap_seq = realm->seq;
invalidate = 1;
} else if (!realm->cached_context) {
dout("update_snap_trace %llx %p seq %lld new\n",
realm->ino, realm, realm->seq);
invalidate = 1;
} else {
dout("update_snap_trace %llx %p seq %lld unchanged\n",
realm->ino, realm, realm->seq);
}
dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
realm, invalidate, p, e);
/* invalidate when we reach the _end_ (root) of the trace */
if (invalidate && p >= e)
rebuild_snap_realms(realm);
if (!first_realm)
first_realm = realm;
else
ceph_put_snap_realm(mdsc, realm);
if (p < e)
goto more;
/*
* queue cap snaps _after_ we've built the new snap contexts,
* so that i_head_snapc can be set appropriately.
*/
while (!list_empty(&dirty_realms)) {
realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
dirty_item);
queue_realm_cap_snaps(realm);
}
if (realm_ret)
*realm_ret = first_realm;
else
ceph_put_snap_realm(mdsc, first_realm);
__cleanup_empty_realms(mdsc);
return 0;
bad:
err = -EINVAL;
fail:
if (realm && !IS_ERR(realm))
ceph_put_snap_realm(mdsc, realm);
if (first_realm)
ceph_put_snap_realm(mdsc, first_realm);
pr_err("update_snap_trace error %d\n", err);
return err;
}
/*
* Send any cap_snaps that are queued for flush. Try to carry
* s_mutex across multiple snap flushes to avoid locking overhead.
*
* Caller holds no locks.
*/
static void flush_snaps(struct ceph_mds_client *mdsc)
{
struct ceph_inode_info *ci;
struct inode *inode;
struct ceph_mds_session *session = NULL;
dout("flush_snaps\n");
spin_lock(&mdsc->snap_flush_lock);
while (!list_empty(&mdsc->snap_flush_list)) {
ci = list_first_entry(&mdsc->snap_flush_list,
struct ceph_inode_info, i_snap_flush_item);
inode = &ci->vfs_inode;
ihold(inode);
spin_unlock(&mdsc->snap_flush_lock);
spin_lock(&ci->i_ceph_lock);
__ceph_flush_snaps(ci, &session, 0);
spin_unlock(&ci->i_ceph_lock);
iput(inode);
spin_lock(&mdsc->snap_flush_lock);
}
spin_unlock(&mdsc->snap_flush_lock);
if (session) {
mutex_unlock(&session->s_mutex);
ceph_put_mds_session(session);
}
dout("flush_snaps done\n");
}
/*
* Handle a snap notification from the MDS.
*
* This can take two basic forms: the simplest is just a snap creation
* or deletion notification on an existing realm. This should update the
* realm and its children.
*
* The more difficult case is realm creation, due to snap creation at a
* new point in the file hierarchy, or due to a rename that moves a file or
* directory into another realm.
*/
void ceph_handle_snap(struct ceph_mds_client *mdsc,
struct ceph_mds_session *session,
struct ceph_msg *msg)
{
struct super_block *sb = mdsc->fsc->sb;
int mds = session->s_mds;
u64 split;
int op;
int trace_len;
struct ceph_snap_realm *realm = NULL;
void *p = msg->front.iov_base;
void *e = p + msg->front.iov_len;
struct ceph_mds_snap_head *h;
int num_split_inos, num_split_realms;
__le64 *split_inos = NULL, *split_realms = NULL;
int i;
int locked_rwsem = 0;
/* decode */
if (msg->front.iov_len < sizeof(*h))
goto bad;
h = p;
op = le32_to_cpu(h->op);
split = le64_to_cpu(h->split); /* non-zero if we are splitting an
* existing realm */
num_split_inos = le32_to_cpu(h->num_split_inos);
num_split_realms = le32_to_cpu(h->num_split_realms);
trace_len = le32_to_cpu(h->trace_len);
p += sizeof(*h);
dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
ceph_snap_op_name(op), split, trace_len);
mutex_lock(&session->s_mutex);
session->s_seq++;
mutex_unlock(&session->s_mutex);
down_write(&mdsc->snap_rwsem);
locked_rwsem = 1;
if (op == CEPH_SNAP_OP_SPLIT) {
struct ceph_mds_snap_realm *ri;
/*
* A "split" breaks part of an existing realm off into
* a new realm. The MDS provides a list of inodes
* (with caps) and child realms that belong to the new
* child.
*/
split_inos = p;
p += sizeof(u64) * num_split_inos;
split_realms = p;
p += sizeof(u64) * num_split_realms;
ceph_decode_need(&p, e, sizeof(*ri), bad);
/* we will peek at realm info here, but will _not_
* advance p, as the realm update will occur below in
* ceph_update_snap_trace. */
ri = p;
realm = ceph_lookup_snap_realm(mdsc, split);
if (!realm) {
realm = ceph_create_snap_realm(mdsc, split);
if (IS_ERR(realm))
goto out;
}
dout("splitting snap_realm %llx %p\n", realm->ino, realm);
for (i = 0; i < num_split_inos; i++) {
struct ceph_vino vino = {
.ino = le64_to_cpu(split_inos[i]),
.snap = CEPH_NOSNAP,
};
struct inode *inode = ceph_find_inode(sb, vino);
struct ceph_inode_info *ci;
struct ceph_snap_realm *oldrealm;
if (!inode)
continue;
ci = ceph_inode(inode);
spin_lock(&ci->i_ceph_lock);
if (!ci->i_snap_realm)
goto skip_inode;
/*
* If this inode belongs to a realm that was
* created after our new realm, we experienced
* a race (due to another split notifications
* arriving from a different MDS). So skip
* this inode.
*/
if (ci->i_snap_realm->created >
le64_to_cpu(ri->created)) {
dout(" leaving %p in newer realm %llx %p\n",
inode, ci->i_snap_realm->ino,
ci->i_snap_realm);
goto skip_inode;
}
dout(" will move %p to split realm %llx %p\n",
inode, realm->ino, realm);
/*
* Move the inode to the new realm
*/
spin_lock(&realm->inodes_with_caps_lock);
list_del_init(&ci->i_snap_realm_item);
list_add(&ci->i_snap_realm_item,
&realm->inodes_with_caps);
oldrealm = ci->i_snap_realm;
ci->i_snap_realm = realm;
spin_unlock(&realm->inodes_with_caps_lock);
spin_unlock(&ci->i_ceph_lock);
ceph_get_snap_realm(mdsc, realm);
ceph_put_snap_realm(mdsc, oldrealm);
iput(inode);
continue;
skip_inode:
spin_unlock(&ci->i_ceph_lock);
iput(inode);
}
/* we may have taken some of the old realm's children. */
for (i = 0; i < num_split_realms; i++) {
struct ceph_snap_realm *child =
__lookup_snap_realm(mdsc,
le64_to_cpu(split_realms[i]));
if (!child)
continue;
adjust_snap_realm_parent(mdsc, child, realm->ino);
}
}
/*
* update using the provided snap trace. if we are deleting a
* snap, we can avoid queueing cap_snaps.
*/
ceph_update_snap_trace(mdsc, p, e,
op == CEPH_SNAP_OP_DESTROY, NULL);
if (op == CEPH_SNAP_OP_SPLIT)
/* we took a reference when we created the realm, above */
ceph_put_snap_realm(mdsc, realm);
__cleanup_empty_realms(mdsc);
up_write(&mdsc->snap_rwsem);
flush_snaps(mdsc);
return;
bad:
pr_err("corrupt snap message from mds%d\n", mds);
ceph_msg_dump(msg);
out:
if (locked_rwsem)
up_write(&mdsc->snap_rwsem);
return;
}
int __init ceph_snap_init(void)
{
ceph_empty_snapc = ceph_create_snap_context(0, GFP_NOFS);
if (!ceph_empty_snapc)
return -ENOMEM;
ceph_empty_snapc->seq = 1;
return 0;
}
void ceph_snap_exit(void)
{
ceph_put_snap_context(ceph_empty_snapc);
}