#include "ubifs.h"
#include <linux/writeback.h>
-#include <asm/div64.h>
+#include <linux/math64.h>
/*
* When pessimistic budget calculations say that there is no enough space,
* UBIFS starts writing back dirty inodes and pages, doing garbage collection,
- * or committing. The below constants define maximum number of times UBIFS
+ * or committing. The below constant defines maximum number of times UBIFS
* repeats the operations.
*/
-#define MAX_SHRINK_RETRIES 8
-#define MAX_GC_RETRIES 4
-#define MAX_CMT_RETRIES 2
-#define MAX_NOSPC_RETRIES 1
+#define MAX_MKSPC_RETRIES 3
/*
* The below constant defines amount of dirty pages which should be written
#define NR_TO_WRITE 16
/**
- * struct retries_info - information about re-tries while making free space.
- * @prev_liability: previous liability
- * @shrink_cnt: how many times the liability was shrinked
- * @shrink_retries: count of liability shrink re-tries (increased when
- * liability does not shrink)
- * @try_gc: GC should be tried first
- * @gc_retries: how many times GC was run
- * @cmt_retries: how many times commit has been done
- * @nospc_retries: how many times GC returned %-ENOSPC
- *
- * Since we consider budgeting to be the fast-path, and this structure has to
- * be allocated on stack and zeroed out, we make it smaller using bit-fields.
- */
-struct retries_info {
- long long prev_liability;
- unsigned int shrink_cnt;
- unsigned int shrink_retries:5;
- unsigned int try_gc:1;
- unsigned int gc_retries:4;
- unsigned int cmt_retries:3;
- unsigned int nospc_retries:1;
-};
-
-/**
* shrink_liability - write-back some dirty pages/inodes.
* @c: UBIFS file-system description object
* @nr_to_write: how many dirty pages to write-back
*
* This function shrinks UBIFS liability by means of writing back some amount
- * of dirty inodes and their pages. Returns the amount of pages which were
- * written back. The returned value does not include dirty inodes which were
- * synchronized.
+ * of dirty inodes and their pages.
*
* Note, this function synchronizes even VFS inodes which are locked
* (@i_mutex) by the caller of the budgeting function, because write-back does
* not touch @i_mutex.
*/
-static int shrink_liability(struct ubifs_info *c, int nr_to_write)
+static void shrink_liability(struct ubifs_info *c, int nr_to_write)
{
- int nr_written;
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- .range_end = LLONG_MAX,
- .nr_to_write = nr_to_write,
- };
-
- generic_sync_sb_inodes(c->vfs_sb, &wbc);
- nr_written = nr_to_write - wbc.nr_to_write;
-
- if (!nr_written) {
- /*
- * Re-try again but wait on pages/inodes which are being
- * written-back concurrently (e.g., by pdflush).
- */
- memset(&wbc, 0, sizeof(struct writeback_control));
- wbc.sync_mode = WB_SYNC_ALL;
- wbc.range_end = LLONG_MAX;
- wbc.nr_to_write = nr_to_write;
- generic_sync_sb_inodes(c->vfs_sb, &wbc);
- nr_written = nr_to_write - wbc.nr_to_write;
- }
-
- dbg_budg("%d pages were written back", nr_written);
- return nr_written;
+ writeback_inodes_sb(c->vfs_sb);
}
-
/**
* run_gc - run garbage collector.
* @c: UBIFS file-system description object
}
/**
+ * get_liability - calculate current liability.
+ * @c: UBIFS file-system description object
+ *
+ * This function calculates and returns current UBIFS liability, i.e. the
+ * amount of bytes UBIFS has "promised" to write to the media.
+ */
+static long long get_liability(struct ubifs_info *c)
+{
+ long long liab;
+
+ spin_lock(&c->space_lock);
+ liab = c->budg_idx_growth + c->budg_data_growth + c->budg_dd_growth;
+ spin_unlock(&c->space_lock);
+ return liab;
+}
+
+/**
* make_free_space - make more free space on the file-system.
* @c: UBIFS file-system description object
- * @ri: information about previous invocations of this function
*
* This function is called when an operation cannot be budgeted because there
* is supposedly no free space. But in most cases there is some free space:
- * o budgeting is pessimistic, so it always budgets more then it is actually
+ * o budgeting is pessimistic, so it always budgets more than it is actually
* needed, so shrinking the liability is one way to make free space - the
* cached data will take less space then it was budgeted for;
* o GC may turn some dark space into free space (budgeting treats dark space
* Returns %-ENOSPC if it couldn't do more free space, and other negative error
* codes on failures.
*/
-static int make_free_space(struct ubifs_info *c, struct retries_info *ri)
+static int make_free_space(struct ubifs_info *c)
{
- int err;
-
- /*
- * If we have some dirty pages and inodes (liability), try to write
- * them back unless this was tried too many times without effect
- * already.
- */
- if (ri->shrink_retries < MAX_SHRINK_RETRIES && !ri->try_gc) {
- long long liability;
-
- spin_lock(&c->space_lock);
- liability = c->budg_idx_growth + c->budg_data_growth +
- c->budg_dd_growth;
- spin_unlock(&c->space_lock);
-
- if (ri->prev_liability >= liability) {
- /* Liability does not shrink, next time try GC then */
- ri->shrink_retries += 1;
- if (ri->gc_retries < MAX_GC_RETRIES)
- ri->try_gc = 1;
- dbg_budg("liability did not shrink: retries %d of %d",
- ri->shrink_retries, MAX_SHRINK_RETRIES);
- }
+ int err, retries = 0;
+ long long liab1, liab2;
- dbg_budg("force write-back (count %d)", ri->shrink_cnt);
- shrink_liability(c, NR_TO_WRITE + ri->shrink_cnt);
+ do {
+ liab1 = get_liability(c);
+ /*
+ * We probably have some dirty pages or inodes (liability), try
+ * to write them back.
+ */
+ dbg_budg("liability %lld, run write-back", liab1);
+ shrink_liability(c, NR_TO_WRITE);
- ri->prev_liability = liability;
- ri->shrink_cnt += 1;
- return -EAGAIN;
- }
+ liab2 = get_liability(c);
+ if (liab2 < liab1)
+ return -EAGAIN;
- /*
- * Try to run garbage collector unless it was already tried too many
- * times.
- */
- if (ri->gc_retries < MAX_GC_RETRIES) {
- ri->gc_retries += 1;
- dbg_budg("run GC, retries %d of %d",
- ri->gc_retries, MAX_GC_RETRIES);
+ dbg_budg("new liability %lld (not shrinked)", liab2);
- ri->try_gc = 0;
+ /* Liability did not shrink again, try GC */
+ dbg_budg("Run GC");
err = run_gc(c);
if (!err)
return -EAGAIN;
- if (err == -EAGAIN) {
- dbg_budg("GC asked to commit");
- err = ubifs_run_commit(c);
- if (err)
- return err;
- return -EAGAIN;
- }
-
- if (err != -ENOSPC)
+ if (err != -EAGAIN && err != -ENOSPC)
+ /* Some real error happened */
return err;
- /*
- * GC could not make any progress. If this is the first time,
- * then it makes sense to try to commit, because it might make
- * some dirty space.
- */
- dbg_budg("GC returned -ENOSPC, retries %d",
- ri->nospc_retries);
- if (ri->nospc_retries >= MAX_NOSPC_RETRIES)
- return err;
- ri->nospc_retries += 1;
- }
-
- /* Neither GC nor write-back helped, try to commit */
- if (ri->cmt_retries < MAX_CMT_RETRIES) {
- ri->cmt_retries += 1;
- dbg_budg("run commit, retries %d of %d",
- ri->cmt_retries, MAX_CMT_RETRIES);
+ dbg_budg("Run commit (retries %d)", retries);
err = ubifs_run_commit(c);
if (err)
return err;
- return -EAGAIN;
- }
+ } while (retries++ < MAX_MKSPC_RETRIES);
+
return -ENOSPC;
}
/**
- * ubifs_calc_min_idx_lebs - calculate amount of eraseblocks for the index.
+ * ubifs_calc_min_idx_lebs - calculate amount of LEBs for the index.
* @c: UBIFS file-system description object
*
- * This function calculates and returns the number of eraseblocks which should
- * be kept for index usage.
+ * This function calculates and returns the number of LEBs which should be kept
+ * for index usage.
*/
int ubifs_calc_min_idx_lebs(struct ubifs_info *c)
{
- int ret;
- uint64_t idx_size;
+ int idx_lebs;
+ long long idx_size;
idx_size = c->old_idx_sz + c->budg_idx_growth + c->budg_uncommitted_idx;
-
/* And make sure we have thrice the index size of space reserved */
- idx_size = idx_size + (idx_size << 1);
-
+ idx_size += idx_size << 1;
/*
* We do not maintain 'old_idx_size' as 'old_idx_lebs'/'old_idx_bytes'
* pair, nor similarly the two variables for the new index size, so we
* have to do this costly 64-bit division on fast-path.
*/
- if (do_div(idx_size, c->leb_size - c->max_idx_node_sz))
- ret = idx_size + 1;
- else
- ret = idx_size;
+ idx_lebs = div_u64(idx_size + c->idx_leb_size - 1, c->idx_leb_size);
/*
* The index head is not available for the in-the-gaps method, so add an
* extra LEB to compensate.
*/
- ret += 1;
- /*
- * At present the index needs at least 2 LEBs: one for the index head
- * and one for in-the-gaps method (which currently does not cater for
- * the index head and so excludes it from consideration).
- */
- if (ret < 2)
- ret = 2;
- return ret;
+ idx_lebs += 1;
+ if (idx_lebs < MIN_INDEX_LEBS)
+ idx_lebs = MIN_INDEX_LEBS;
+ return idx_lebs;
}
/**
*/
static int can_use_rp(struct ubifs_info *c)
{
- if (current->fsuid == c->rp_uid || capable(CAP_SYS_RESOURCE) ||
+ if (current_fsuid() == c->rp_uid || capable(CAP_SYS_RESOURCE) ||
(c->rp_gid != 0 && in_group_p(c->rp_gid)))
return 1;
return 0;
* do_budget_space - reserve flash space for index and data growth.
* @c: UBIFS file-system description object
*
- * This function makes sure UBIFS has enough free eraseblocks for index growth
- * and data.
+ * This function makes sure UBIFS has enough free LEBs for index growth and
+ * data.
*
* 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 3,
- * and makes sure this does not exceed the amount of free eraseblocks.
+ * and makes sure this does not exceed the amount of free LEBs.
*
* Notes about @c->min_idx_lebs and @c->lst.idx_lebs variables:
* o @c->lst.idx_lebs is the number of LEBs the index currently uses. It might
* be large, because UBIFS does not do any index consolidation as long as
* there is free space. IOW, the index may take a lot of LEBs, but the LEBs
* will contain a lot of dirt.
- * o @c->min_idx_lebs is the the index presumably takes. IOW, the index may be
- * consolidated to take up to @c->min_idx_lebs LEBs.
+ * o @c->min_idx_lebs is the number of LEBS the index presumably takes. IOW,
+ * the index may be consolidated to take up to @c->min_idx_lebs LEBs.
*
* This function returns zero in case of success, and %-ENOSPC in case of
* failure.
* @c->lst.empty_lebs + @c->freeable_cnt + @c->idx_gc_cnt -
* @c->lst.taken_empty_lebs
*
- * @empty_lebs are available because they are empty. @freeable_cnt are
- * available because they contain only free and dirty space and the
- * index allocation always occurs after wbufs are synch'ed.
- * @idx_gc_cnt are available because they are index LEBs that have been
- * garbage collected (including trivial GC) and are awaiting the commit
- * before they can be unmapped - note that the in-the-gaps method will
- * grab these if it needs them. @taken_empty_lebs are empty_lebs that
- * have already been allocated for some purpose (also includes those
- * LEBs on the @idx_gc list).
+ * @c->lst.empty_lebs are available because they are empty.
+ * @c->freeable_cnt are available because they contain only free and
+ * dirty space, @c->idx_gc_cnt are available because they are index
+ * LEBs that have been garbage collected and are awaiting the commit
+ * before they can be used. And the in-the-gaps method will grab these
+ * if it needs them. @c->lst.taken_empty_lebs are empty LEBs that have
+ * already been allocated for some purpose.
*
- * Note, @taken_empty_lebs may temporarily be higher by one because of
- * the way we serialize LEB allocations and budgeting. See a comment in
- * 'ubifs_find_free_space()'.
+ * Note, @c->idx_gc_cnt is included to both @c->lst.empty_lebs (because
+ * these LEBs are empty) and to @c->lst.taken_empty_lebs (because they
+ * are taken until after the commit).
+ *
+ * Note, @c->lst.taken_empty_lebs may temporarily be higher by one
+ * because of the way we serialize LEB allocations and budgeting. See a
+ * comment in 'ubifs_find_free_space()'.
*/
lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
c->lst.taken_empty_lebs;
int ubifs_budget_space(struct ubifs_info *c, struct ubifs_budget_req *req)
{
int uninitialized_var(cmt_retries), uninitialized_var(wb_retries);
- int err, idx_growth, data_growth, dd_growth;
- struct retries_info ri;
+ int err, idx_growth, data_growth, dd_growth, retried = 0;
ubifs_assert(req->new_page <= 1);
ubifs_assert(req->dirtied_page <= 1);
if (!data_growth && !dd_growth)
return 0;
idx_growth = calc_idx_growth(c, req);
- memset(&ri, 0, sizeof(struct retries_info));
again:
spin_lock(&c->space_lock);
return err;
}
- err = make_free_space(c, &ri);
+ err = make_free_space(c);
+ cond_resched();
if (err == -EAGAIN) {
dbg_budg("try again");
- cond_resched();
goto again;
} else if (err == -ENOSPC) {
+ if (!retried) {
+ retried = 1;
+ dbg_budg("-ENOSPC, but anyway try once again");
+ goto again;
+ }
dbg_budg("FS is full, -ENOSPC");
c->nospace = 1;
if (can_use_rp(c) || c->rp_size == 0)
* @c: UBIFS file-system description object
*
* This function converts budget which was allocated for a new page of data to
- * the budget of changing an existing page of data. The latter is smaller then
+ * the budget of changing an existing page of data. The latter is smaller than
* the former, so this function only does simple re-calculation and does not
* involve any write-back.
*/
*
* This function releases budget corresponding to a dirty inode. It is usually
* called when after the inode has been written to the media and marked as
- * clean.
+ * clean. It also causes the "no space" flags to be cleared.
*/
void ubifs_release_dirty_inode_budget(struct ubifs_info *c,
struct ubifs_inode *ui)
struct ubifs_budget_req req;
memset(&req, 0, sizeof(struct ubifs_budget_req));
+ /* The "no space" flags will be cleared because dd_growth is > 0 */
req.dd_growth = c->inode_budget + ALIGN(ui->data_len, 8);
ubifs_release_budget(c, &req);
}
* 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.
+ * node and it has to write indexing nodes as well. This introduces additional
+ * overhead, and UBIFS has to report slightly less free space to meet the above
+ * expectations.
*
* 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
* 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)
+long long ubifs_reported_space(const struct ubifs_info *c, long long free)
{
- int divisor, factor;
+ 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 is 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
+ * 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
+ * Note, the multiplier 3 is because UBIFS reserves 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) / ((c->fanout >> 1) - 1);
+ divisor += (c->max_idx_node_sz * 3) / (f - 1);
free *= factor;
- do_div(free, divisor);
- return free;
+ return div_u64(free, divisor);
}
/**
- * ubifs_budg_get_free_space - return amount of free space.
+ * ubifs_get_free_space_nolock - 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,
+ * alignment, wastage at the end of LEBs, etc), it cannot report real amount of
+ * free flash space it has (well, because not all dirty space is reclaimable,
+ * UBIFS does not actually know the real amount). If UBIFS did so, it would
+ * bread user expectations 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_nolock(struct ubifs_info *c)
{
- int min_idx_lebs;
+ int rsvd_idx_lebs, lebs;
long long available, outstanding, free;
- spin_lock(&c->space_lock);
- min_idx_lebs = ubifs_calc_min_idx_lebs(c);
+ ubifs_assert(c->min_idx_lebs == ubifs_calc_min_idx_lebs(c));
outstanding = c->budg_data_growth + c->budg_dd_growth;
+ available = ubifs_calc_available(c, c->min_idx_lebs);
/*
- * Force the amount available to the total size reported if the used
- * space is zero.
+ * 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 (c->lst.total_used <= UBIFS_INO_NODE_SZ && !outstanding) {
- spin_unlock(&c->space_lock);
- return (long long)c->block_cnt << UBIFS_BLOCK_SHIFT;
- }
-
- available = ubifs_calc_available(c, min_idx_lebs);
- spin_unlock(&c->space_lock);
+ if (c->min_idx_lebs > c->lst.idx_lebs)
+ rsvd_idx_lebs = c->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);
if (available > outstanding)
free = ubifs_reported_space(c, available - outstanding);
free = 0;
return free;
}
+
+/**
+ * ubifs_get_free_space - return amount of free space.
+ * @c: UBIFS file-system description object
+ *
+ * This function calculates and returns amount of free space to report to
+ * user-space.
+ */
+long long ubifs_get_free_space(struct ubifs_info *c)
+{
+ long long free;
+
+ spin_lock(&c->space_lock);
+ free = ubifs_get_free_space_nolock(c);
+ spin_unlock(&c->space_lock);
+
+ return free;
+}
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