#include "xfs_trans.h"
#include "xfs_bit.h"
#include "xfs_refcount.h"
+#include "xfs_rmap.h"
/* Allowable refcount adjustment amounts. */
enum xfs_refc_adjust_op {
XFS_REFCOUNT_ADJUST_INCREASE = 1,
XFS_REFCOUNT_ADJUST_DECREASE = -1,
+ XFS_REFCOUNT_ADJUST_COW_ALLOC = 0,
+ XFS_REFCOUNT_ADJUST_COW_FREE = -1,
};
+STATIC int __xfs_refcount_cow_alloc(struct xfs_btree_cur *rcur,
+ xfs_agblock_t agbno, xfs_extlen_t aglen,
+ struct xfs_defer_ops *dfops);
+STATIC int __xfs_refcount_cow_free(struct xfs_btree_cur *rcur,
+ xfs_agblock_t agbno, xfs_extlen_t aglen,
+ struct xfs_defer_ops *dfops);
+
/*
* Look up the first record less than or equal to [bno, len] in the btree
* given by cur.
return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
}
+/* Convert on-disk record to in-core format. */
+static inline void
+xfs_refcount_btrec_to_irec(
+ union xfs_btree_rec *rec,
+ struct xfs_refcount_irec *irec)
+{
+ irec->rc_startblock = be32_to_cpu(rec->refc.rc_startblock);
+ irec->rc_blockcount = be32_to_cpu(rec->refc.rc_blockcount);
+ irec->rc_refcount = be32_to_cpu(rec->refc.rc_refcount);
+}
+
/*
* Get the data from the pointed-to record.
*/
struct xfs_refcount_irec *irec,
int *stat)
{
- union xfs_btree_rec *rec;
- int error;
+ union xfs_btree_rec *rec;
+ int error;
error = xfs_btree_get_rec(cur, &rec, stat);
if (!error && *stat == 1) {
- irec->rc_startblock = be32_to_cpu(rec->refc.rc_startblock);
- irec->rc_blockcount = be32_to_cpu(rec->refc.rc_blockcount);
- irec->rc_refcount = be32_to_cpu(rec->refc.rc_refcount);
+ xfs_refcount_btrec_to_irec(rec, irec);
trace_xfs_refcount_get(cur->bc_mp, cur->bc_private.a.agno,
irec);
}
return error;
}
+#define XFS_FIND_RCEXT_SHARED 1
+#define XFS_FIND_RCEXT_COW 2
/*
* Find the left extent and the one after it (cleft). This function assumes
* that we've already split any extent crossing agbno.
struct xfs_refcount_irec *left,
struct xfs_refcount_irec *cleft,
xfs_agblock_t agbno,
- xfs_extlen_t aglen)
+ xfs_extlen_t aglen,
+ int flags)
{
struct xfs_refcount_irec tmp;
int error;
if (xfs_refc_next(&tmp) != agbno)
return 0;
+ if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
+ return 0;
+ if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
+ return 0;
/* We have a left extent; retrieve (or invent) the next right one */
*left = tmp;
struct xfs_refcount_irec *right,
struct xfs_refcount_irec *cright,
xfs_agblock_t agbno,
- xfs_extlen_t aglen)
+ xfs_extlen_t aglen,
+ int flags)
{
struct xfs_refcount_irec tmp;
int error;
if (tmp.rc_startblock != agbno + aglen)
return 0;
+ if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
+ return 0;
+ if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
+ return 0;
/* We have a right extent; retrieve (or invent) the next left one */
*right = tmp;
xfs_agblock_t *agbno,
xfs_extlen_t *aglen,
enum xfs_refc_adjust_op adjust,
+ int flags,
bool *shape_changed)
{
struct xfs_refcount_irec left = {0}, cleft = {0};
* [right].
*/
error = xfs_refcount_find_left_extents(cur, &left, &cleft, *agbno,
- *aglen);
+ *aglen, flags);
if (error)
return error;
error = xfs_refcount_find_right_extents(cur, &right, &cright, *agbno,
- *aglen);
+ *aglen, flags);
if (error)
return error;
* Try to merge with the left or right extents of the range.
*/
error = xfs_refcount_merge_extents(cur, new_agbno, new_aglen, adj,
- &shape_changed);
+ XFS_FIND_RCEXT_SHARED, &shape_changed);
if (error)
goto out_error;
if (shape_changed)
new_len, XFS_REFCOUNT_ADJUST_DECREASE, dfops, NULL);
*new_fsb = XFS_AGB_TO_FSB(mp, agno, new_agbno);
break;
+ case XFS_REFCOUNT_ALLOC_COW:
+ *new_fsb = startblock + blockcount;
+ *new_len = 0;
+ error = __xfs_refcount_cow_alloc(rcur, bno, blockcount, dfops);
+ break;
+ case XFS_REFCOUNT_FREE_COW:
+ *new_fsb = startblock + blockcount;
+ *new_len = 0;
+ error = __xfs_refcount_cow_free(rcur, bno, blockcount, dfops);
+ break;
default:
ASSERT(0);
error = -EFSCORRUPTED;
cur->bc_private.a.agno, error, _RET_IP_);
return error;
}
+
+/*
+ * Recovering CoW Blocks After a Crash
+ *
+ * Due to the way that the copy on write mechanism works, there's a window of
+ * opportunity in which we can lose track of allocated blocks during a crash.
+ * Because CoW uses delayed allocation in the in-core CoW fork, writeback
+ * causes blocks to be allocated and stored in the CoW fork. The blocks are
+ * no longer in the free space btree but are not otherwise recorded anywhere
+ * until the write completes and the blocks are mapped into the file. A crash
+ * in between allocation and remapping results in the replacement blocks being
+ * lost. This situation is exacerbated by the CoW extent size hint because
+ * allocations can hang around for long time.
+ *
+ * However, there is a place where we can record these allocations before they
+ * become mappings -- the reference count btree. The btree does not record
+ * extents with refcount == 1, so we can record allocations with a refcount of
+ * 1. Blocks being used for CoW writeout cannot be shared, so there should be
+ * no conflict with shared block records. These mappings should be created
+ * when we allocate blocks to the CoW fork and deleted when they're removed
+ * from the CoW fork.
+ *
+ * Minor nit: records for in-progress CoW allocations and records for shared
+ * extents must never be merged, to preserve the property that (except for CoW
+ * allocations) there are no refcount btree entries with refcount == 1. The
+ * only time this could potentially happen is when unsharing a block that's
+ * adjacent to CoW allocations, so we must be careful to avoid this.
+ *
+ * At mount time we recover lost CoW allocations by searching the refcount
+ * btree for these refcount == 1 mappings. These represent CoW allocations
+ * that were in progress at the time the filesystem went down, so we can free
+ * them to get the space back.
+ *
+ * This mechanism is superior to creating EFIs for unmapped CoW extents for
+ * several reasons -- first, EFIs pin the tail of the log and would have to be
+ * periodically relogged to avoid filling up the log. Second, CoW completions
+ * will have to file an EFD and create new EFIs for whatever remains in the
+ * CoW fork; this partially takes care of (1) but extent-size reservations
+ * will have to periodically relog even if there's no writeout in progress.
+ * This can happen if the CoW extent size hint is set, which you really want.
+ * Third, EFIs cannot currently be automatically relogged into newer
+ * transactions to advance the log tail. Fourth, stuffing the log full of
+ * EFIs places an upper bound on the number of CoW allocations that can be
+ * held filesystem-wide at any given time. Recording them in the refcount
+ * btree doesn't require us to maintain any state in memory and doesn't pin
+ * the log.
+ */
+/*
+ * Adjust the refcounts of CoW allocations. These allocations are "magic"
+ * in that they're not referenced anywhere else in the filesystem, so we
+ * stash them in the refcount btree with a refcount of 1 until either file
+ * remapping (or CoW cancellation) happens.
+ */
+STATIC int
+xfs_refcount_adjust_cow_extents(
+ struct xfs_btree_cur *cur,
+ xfs_agblock_t agbno,
+ xfs_extlen_t aglen,
+ enum xfs_refc_adjust_op adj,
+ struct xfs_defer_ops *dfops,
+ struct xfs_owner_info *oinfo)
+{
+ struct xfs_refcount_irec ext, tmp;
+ int error;
+ int found_rec, found_tmp;
+
+ if (aglen == 0)
+ return 0;
+
+ /* Find any overlapping refcount records */
+ error = xfs_refcount_lookup_ge(cur, agbno, &found_rec);
+ if (error)
+ goto out_error;
+ error = xfs_refcount_get_rec(cur, &ext, &found_rec);
+ if (error)
+ goto out_error;
+ if (!found_rec) {
+ ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks +
+ XFS_REFC_COW_START;
+ ext.rc_blockcount = 0;
+ ext.rc_refcount = 0;
+ }
+
+ switch (adj) {
+ case XFS_REFCOUNT_ADJUST_COW_ALLOC:
+ /* Adding a CoW reservation, there should be nothing here. */
+ XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
+ ext.rc_startblock >= agbno + aglen, out_error);
+
+ tmp.rc_startblock = agbno;
+ tmp.rc_blockcount = aglen;
+ tmp.rc_refcount = 1;
+ trace_xfs_refcount_modify_extent(cur->bc_mp,
+ cur->bc_private.a.agno, &tmp);
+
+ error = xfs_refcount_insert(cur, &tmp,
+ &found_tmp);
+ if (error)
+ goto out_error;
+ XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
+ found_tmp == 1, out_error);
+ break;
+ case XFS_REFCOUNT_ADJUST_COW_FREE:
+ /* Removing a CoW reservation, there should be one extent. */
+ XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
+ ext.rc_startblock == agbno, out_error);
+ XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
+ ext.rc_blockcount == aglen, out_error);
+ XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
+ ext.rc_refcount == 1, out_error);
+
+ ext.rc_refcount = 0;
+ trace_xfs_refcount_modify_extent(cur->bc_mp,
+ cur->bc_private.a.agno, &ext);
+ error = xfs_refcount_delete(cur, &found_rec);
+ if (error)
+ goto out_error;
+ XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
+ found_rec == 1, out_error);
+ break;
+ default:
+ ASSERT(0);
+ }
+
+ return error;
+out_error:
+ trace_xfs_refcount_modify_extent_error(cur->bc_mp,
+ cur->bc_private.a.agno, error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Add or remove refcount btree entries for CoW reservations.
+ */
+STATIC int
+xfs_refcount_adjust_cow(
+ struct xfs_btree_cur *cur,
+ xfs_agblock_t agbno,
+ xfs_extlen_t aglen,
+ enum xfs_refc_adjust_op adj,
+ struct xfs_defer_ops *dfops)
+{
+ bool shape_changed;
+ int error;
+
+ agbno += XFS_REFC_COW_START;
+
+ /*
+ * Ensure that no rcextents cross the boundary of the adjustment range.
+ */
+ error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
+ if (error)
+ goto out_error;
+
+ error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
+ if (error)
+ goto out_error;
+
+ /*
+ * Try to merge with the left or right extents of the range.
+ */
+ error = xfs_refcount_merge_extents(cur, &agbno, &aglen, adj,
+ XFS_FIND_RCEXT_COW, &shape_changed);
+ if (error)
+ goto out_error;
+
+ /* Now that we've taken care of the ends, adjust the middle extents */
+ error = xfs_refcount_adjust_cow_extents(cur, agbno, aglen, adj,
+ dfops, NULL);
+ if (error)
+ goto out_error;
+
+ return 0;
+
+out_error:
+ trace_xfs_refcount_adjust_cow_error(cur->bc_mp, cur->bc_private.a.agno,
+ error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Record a CoW allocation in the refcount btree.
+ */
+STATIC int
+__xfs_refcount_cow_alloc(
+ struct xfs_btree_cur *rcur,
+ xfs_agblock_t agbno,
+ xfs_extlen_t aglen,
+ struct xfs_defer_ops *dfops)
+{
+ int error;
+
+ trace_xfs_refcount_cow_increase(rcur->bc_mp, rcur->bc_private.a.agno,
+ agbno, aglen);
+
+ /* Add refcount btree reservation */
+ error = xfs_refcount_adjust_cow(rcur, agbno, aglen,
+ XFS_REFCOUNT_ADJUST_COW_ALLOC, dfops);
+ if (error)
+ return error;
+
+ /* Add rmap entry */
+ if (xfs_sb_version_hasrmapbt(&rcur->bc_mp->m_sb)) {
+ error = xfs_rmap_alloc_extent(rcur->bc_mp, dfops,
+ rcur->bc_private.a.agno,
+ agbno, aglen, XFS_RMAP_OWN_COW);
+ if (error)
+ return error;
+ }
+
+ return error;
+}
+
+/*
+ * Remove a CoW allocation from the refcount btree.
+ */
+STATIC int
+__xfs_refcount_cow_free(
+ struct xfs_btree_cur *rcur,
+ xfs_agblock_t agbno,
+ xfs_extlen_t aglen,
+ struct xfs_defer_ops *dfops)
+{
+ int error;
+
+ trace_xfs_refcount_cow_decrease(rcur->bc_mp, rcur->bc_private.a.agno,
+ agbno, aglen);
+
+ /* Remove refcount btree reservation */
+ error = xfs_refcount_adjust_cow(rcur, agbno, aglen,
+ XFS_REFCOUNT_ADJUST_COW_FREE, dfops);
+ if (error)
+ return error;
+
+ /* Remove rmap entry */
+ if (xfs_sb_version_hasrmapbt(&rcur->bc_mp->m_sb)) {
+ error = xfs_rmap_free_extent(rcur->bc_mp, dfops,
+ rcur->bc_private.a.agno,
+ agbno, aglen, XFS_RMAP_OWN_COW);
+ if (error)
+ return error;
+ }
+
+ return error;
+}
+
+/* Record a CoW staging extent in the refcount btree. */
+int
+xfs_refcount_alloc_cow_extent(
+ struct xfs_mount *mp,
+ struct xfs_defer_ops *dfops,
+ xfs_fsblock_t fsb,
+ xfs_extlen_t len)
+{
+ if (!xfs_sb_version_hasreflink(&mp->m_sb))
+ return 0;
+
+ return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_ALLOC_COW,
+ fsb, len);
+}
+
+/* Forget a CoW staging event in the refcount btree. */
+int
+xfs_refcount_free_cow_extent(
+ struct xfs_mount *mp,
+ struct xfs_defer_ops *dfops,
+ xfs_fsblock_t fsb,
+ xfs_extlen_t len)
+{
+ if (!xfs_sb_version_hasreflink(&mp->m_sb))
+ return 0;
+
+ return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_FREE_COW,
+ fsb, len);
+}
+
+struct xfs_refcount_recovery {
+ struct list_head rr_list;
+ struct xfs_refcount_irec rr_rrec;
+};
+
+/* Stuff an extent on the recovery list. */
+STATIC int
+xfs_refcount_recover_extent(
+ struct xfs_btree_cur *cur,
+ union xfs_btree_rec *rec,
+ void *priv)
+{
+ struct list_head *debris = priv;
+ struct xfs_refcount_recovery *rr;
+
+ if (be32_to_cpu(rec->refc.rc_refcount) != 1)
+ return -EFSCORRUPTED;
+
+ rr = kmem_alloc(sizeof(struct xfs_refcount_recovery), KM_SLEEP);
+ xfs_refcount_btrec_to_irec(rec, &rr->rr_rrec);
+ list_add_tail(&rr->rr_list, debris);
+
+ return 0;
+}
+
+/* Find and remove leftover CoW reservations. */
+int
+xfs_refcount_recover_cow_leftovers(
+ struct xfs_mount *mp,
+ xfs_agnumber_t agno)
+{
+ struct xfs_trans *tp;
+ struct xfs_btree_cur *cur;
+ struct xfs_buf *agbp;
+ struct xfs_refcount_recovery *rr, *n;
+ struct list_head debris;
+ union xfs_btree_irec low;
+ union xfs_btree_irec high;
+ struct xfs_defer_ops dfops;
+ xfs_fsblock_t fsb;
+ xfs_agblock_t agbno;
+ int error;
+
+ if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START)
+ return -EOPNOTSUPP;
+
+ error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);
+ if (error)
+ return error;
+ cur = xfs_refcountbt_init_cursor(mp, NULL, agbp, agno, NULL);
+
+ /* Find all the leftover CoW staging extents. */
+ INIT_LIST_HEAD(&debris);
+ memset(&low, 0, sizeof(low));
+ memset(&high, 0, sizeof(high));
+ low.rc.rc_startblock = XFS_REFC_COW_START;
+ high.rc.rc_startblock = -1U;
+ error = xfs_btree_query_range(cur, &low, &high,
+ xfs_refcount_recover_extent, &debris);
+ if (error)
+ goto out_error;
+ xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+ xfs_buf_relse(agbp);
+
+ /* Now iterate the list to free the leftovers */
+ list_for_each_entry(rr, &debris, rr_list) {
+ /* Set up transaction. */
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
+ if (error)
+ goto out_free;
+
+ trace_xfs_refcount_recover_extent(mp, agno, &rr->rr_rrec);
+
+ /* Free the orphan record */
+ xfs_defer_init(&dfops, &fsb);
+ agbno = rr->rr_rrec.rc_startblock - XFS_REFC_COW_START;
+ fsb = XFS_AGB_TO_FSB(mp, agno, agbno);
+ error = xfs_refcount_free_cow_extent(mp, &dfops, fsb,
+ rr->rr_rrec.rc_blockcount);
+ if (error)
+ goto out_defer;
+
+ /* Free the block. */
+ xfs_bmap_add_free(mp, &dfops, fsb,
+ rr->rr_rrec.rc_blockcount, NULL);
+
+ error = xfs_defer_finish(&tp, &dfops, NULL);
+ if (error)
+ goto out_defer;
+
+ error = xfs_trans_commit(tp);
+ if (error)
+ goto out_cancel;
+ }
+ goto out_free;
+
+out_defer:
+ xfs_defer_cancel(&dfops);
+out_cancel:
+ xfs_trans_cancel(tp);
+
+out_free:
+ /* Free the leftover list */
+ list_for_each_entry_safe(rr, n, &debris, rr_list) {
+ list_del(&rr->rr_list);
+ kmem_free(rr);
+ }
+
+ return error;
+
+out_error:
+ xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+ xfs_buf_relse(agbp);
+ return error;
+}
projects / thirdparty / xfsprogs-dev.git / commitdiff
