idx_size = c->old_idx_sz + c->budg_idx_growth + c->budg_uncommitted_idx;
- /* And make sure we have twice the index size of space reserved */
- idx_size <<= 1;
+ /* And make sure we have thrice the index size of space reserved */
+ idx_size = idx_size + (idx_size << 1);
/*
* We do not maintain 'old_idx_size' as 'old_idx_lebs'/'old_idx_bytes'
int subtract_lebs;
long long available;
- /*
- * Force the amount available to the total size reported if the used
- * space is zero.
- */
- if (c->lst.total_used <= UBIFS_INO_NODE_SZ &&
- c->budg_data_growth + c->budg_dd_growth == 0) {
- /* Do the same calculation as for c->block_cnt */
- available = c->main_lebs - 2;
- available *= c->leb_size - c->dark_wm;
- return available;
- }
-
available = c->main_bytes - c->lst.total_used;
/*
* This function makes sure UBIFS has enough free eraseblocks for index growth
* and data.
*
- * When budgeting index space, UBIFS reserves twice as more LEBs as the index
+ * When budgeting index space, UBIFS reserves thrice as many LEBs as the index
* would take if it was consolidated and written to the flash. This guarantees
* that the "in-the-gaps" commit method always succeeds and UBIFS will always
* be able to commit dirty index. So this function basically adds amount of
- * budgeted index space to the size of the current index, multiplies this by 2,
+ * budgeted index space to the size of the current index, multiplies this by 3,
* and makes sure this does not exceed the amount of free eraseblocks.
*
* Notes about @c->min_idx_lebs and @c->lst.idx_lebs variables:
int err, idx_growth, data_growth, dd_growth;
struct retries_info ri;
+ ubifs_assert(req->new_page <= 1);
+ ubifs_assert(req->dirtied_page <= 1);
+ ubifs_assert(req->new_dent <= 1);
+ ubifs_assert(req->mod_dent <= 1);
+ ubifs_assert(req->new_ino <= 1);
+ ubifs_assert(req->new_ino_d <= UBIFS_MAX_INO_DATA);
ubifs_assert(req->dirtied_ino <= 4);
ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
+ ubifs_assert(!(req->new_ino_d & 7));
+ ubifs_assert(!(req->dirtied_ino_d & 7));
data_growth = calc_data_growth(c, req);
dd_growth = calc_dd_growth(c, req);
*/
void ubifs_release_budget(struct ubifs_info *c, struct ubifs_budget_req *req)
{
+ ubifs_assert(req->new_page <= 1);
+ ubifs_assert(req->dirtied_page <= 1);
+ ubifs_assert(req->new_dent <= 1);
+ ubifs_assert(req->mod_dent <= 1);
+ ubifs_assert(req->new_ino <= 1);
+ ubifs_assert(req->new_ino_d <= UBIFS_MAX_INO_DATA);
ubifs_assert(req->dirtied_ino <= 4);
ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
+ ubifs_assert(!(req->new_ino_d & 7));
+ ubifs_assert(!(req->dirtied_ino_d & 7));
if (!req->recalculate) {
ubifs_assert(req->idx_growth >= 0);
ubifs_assert(req->data_growth >= 0);
ubifs_assert(c->budg_idx_growth >= 0);
ubifs_assert(c->budg_data_growth >= 0);
+ ubifs_assert(c->budg_dd_growth >= 0);
ubifs_assert(c->min_idx_lebs < c->main_lebs);
+ ubifs_assert(!(c->budg_idx_growth & 7));
+ ubifs_assert(!(c->budg_data_growth & 7));
+ ubifs_assert(!(c->budg_dd_growth & 7));
spin_unlock(&c->space_lock);
}
void ubifs_release_dirty_inode_budget(struct ubifs_info *c,
struct ubifs_inode *ui)
{
- struct ubifs_budget_req req = {.dd_growth = c->inode_budget,
- .dirtied_ino_d = ui->data_len};
+ struct ubifs_budget_req req;
+ memset(&req, 0, sizeof(struct ubifs_budget_req));
+ req.dd_growth = c->inode_budget + ALIGN(ui->data_len, 8);
ubifs_release_budget(c, &req);
}
/**
- * ubifs_budg_get_free_space - return amount of free space.
+ * ubifs_reported_space - calculate reported free space.
+ * @c: the UBIFS file-system description object
+ * @free: amount of free space
+ *
+ * This function calculates amount of free space which will be reported to
+ * user-space. User-space application tend to expect that if the file-system
+ * (e.g., via the 'statfs()' call) reports that it has N bytes available, they
+ * are able to write a file of size N. UBIFS attaches node headers to each data
+ * node and it has to write indexind nodes as well. This introduces additional
+ * overhead, and UBIFS it has to report sligtly less free space to meet the
+ * above expectetion.
+ *
+ * This function assumes free space is made up of uncompressed data nodes and
+ * full index nodes (one per data node, tripled because we always allow enough
+ * space to write the index thrice).
+ *
+ * Note, the calculation is pessimistic, which means that most of the time
+ * UBIFS reports less space than it actually has.
+ */
+long long ubifs_reported_space(const struct ubifs_info *c, uint64_t free)
+{
+ int divisor, factor, f;
+
+ /*
+ * Reported space size is @free * X, where X is UBIFS block size
+ * divided by UBIFS block size + all overhead one data block
+ * introduces. The overhead is the node header + indexing overhead.
+ *
+ * Indexing overhead calculations are based on the following formula:
+ * I = N/(f - 1) + 1, where I - number of indexing nodes, N - number
+ * of data nodes, f - fanout. Because effective UBIFS fanout is twice
+ * as less than maximum fanout, we assume that each data node
+ * introduces 3 * @c->max_idx_node_sz / (@c->fanout/2 - 1) bytes.
+ * Note, the multiplier 3 is because UBIFS reseves thrice as more space
+ * for the index.
+ */
+ f = c->fanout > 3 ? c->fanout >> 1 : 2;
+ factor = UBIFS_BLOCK_SIZE;
+ divisor = UBIFS_MAX_DATA_NODE_SZ;
+ divisor += (c->max_idx_node_sz * 3) / (f - 1);
+ free *= factor;
+ do_div(free, divisor);
+ return free;
+}
+
+/**
+ * ubifs_get_free_space - return amount of free space.
* @c: UBIFS file-system description object
*
- * This function returns amount of free space on the file-system.
+ * This function calculates amount of free space to report to user-space.
+ *
+ * Because UBIFS may introduce substantial overhead (the index, node headers,
+ * alighment, wastage at the end of eraseblocks, etc), it cannot report real
+ * amount of free flash space it has (well, because not all dirty space is
+ * reclamable, UBIFS does not actually know the real amount). If UBIFS did so,
+ * it would bread user expectetion about what free space is. Users seem to
+ * accustomed to assume that if the file-system reports N bytes of free space,
+ * they would be able to fit a file of N bytes to the FS. This almost works for
+ * traditional file-systems, because they have way less overhead than UBIFS.
+ * So, to keep users happy, UBIFS tries to take the overhead into account.
*/
-long long ubifs_budg_get_free_space(struct ubifs_info *c)
+long long ubifs_get_free_space(struct ubifs_info *c)
{
- int min_idx_lebs, rsvd_idx_lebs;
+ int min_idx_lebs, rsvd_idx_lebs, lebs;
long long available, outstanding, free;
- /* Do exactly the same calculations as in 'do_budget_space()' */
spin_lock(&c->space_lock);
min_idx_lebs = ubifs_calc_min_idx_lebs(c);
+ outstanding = c->budg_data_growth + c->budg_dd_growth;
- if (min_idx_lebs > c->lst.idx_lebs)
- rsvd_idx_lebs = min_idx_lebs - c->lst.idx_lebs;
- else
- rsvd_idx_lebs = 0;
-
- if (rsvd_idx_lebs > c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt
- - c->lst.taken_empty_lebs) {
+ /*
+ * Force the amount available to the total size reported if the used
+ * space is zero.
+ */
+ if (c->lst.total_used <= UBIFS_INO_NODE_SZ && !outstanding) {
spin_unlock(&c->space_lock);
- return 0;
+ return (long long)c->block_cnt << UBIFS_BLOCK_SHIFT;
}
available = ubifs_calc_available(c, min_idx_lebs);
- outstanding = c->budg_data_growth + c->budg_dd_growth;
- c->min_idx_lebs = min_idx_lebs;
+
+ /*
+ * When reporting free space to user-space, UBIFS guarantees that it is
+ * possible to write a file of free space size. This means that for
+ * empty LEBs we may use more precise calculations than
+ * 'ubifs_calc_available()' is using. Namely, we know that in empty
+ * LEBs we would waste only @c->leb_overhead bytes, not @c->dark_wm.
+ * Thus, amend the available space.
+ *
+ * Note, the calculations below are similar to what we have in
+ * 'do_budget_space()', so refer there for comments.
+ */
+ if (min_idx_lebs > c->lst.idx_lebs)
+ rsvd_idx_lebs = min_idx_lebs - c->lst.idx_lebs;
+ else
+ rsvd_idx_lebs = 0;
+ lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
+ c->lst.taken_empty_lebs;
+ lebs -= rsvd_idx_lebs;
+ available += lebs * (c->dark_wm - c->leb_overhead);
spin_unlock(&c->space_lock);
if (available > outstanding)
git.openpandora.org / pandora-kernel.git / blobdiff