Merge branch 'linux-next' of git://git.infradead.org/~dedekind/ubifs-2.6

* 'linux-next' of git://git.infradead.org/~dedekind/ubifs-2.6:
  UBIFS: make minimum fanout 3
  UBIFS: fix division by zero
  UBIFS: amend f_fsid
  UBIFS: fill f_fsid
  UBIFS: improve statfs reporting even more
  UBIFS: introduce LEB overhead
  UBIFS: add forgotten gc_idx_lebs component
  UBIFS: fix assertion
  UBIFS: improve statfs reporting
  UBIFS: remove incorrect index space check
  UBIFS: push empty flash hack down
  UBIFS: do not update min_idx_lebs in stafs
  UBIFS: allow for racing between GC and TNC
  UBIFS: always read hashed-key nodes under TNC mutex
  UBIFS: fix zero-length truncations

Author: torvalds

fs/ubifs/budget.c

@@ -302,18 +302,6 @@ long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs)
 	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;
 
 	/*
@@ -714,34 +702,106 @@ void ubifs_release_dirty_inode_budget(struct ubifs_info *c,
 }
 
 /**
- * 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)

fs/ubifs/dir.c

@@ -587,7 +587,6 @@ static int ubifs_unlink(struct inode *dir, struct dentry *dentry)
 	if (err) {
 		if (err != -ENOSPC)
 			return err;
-		err = 0;
 		budgeted = 0;
 	}
 

fs/ubifs/file.c

@@ -793,7 +793,7 @@ static int do_truncation(struct ubifs_info *c, struct inode *inode,
 	int err;
 	struct ubifs_budget_req req;
 	loff_t old_size = inode->i_size, new_size = attr->ia_size;
-	int offset = new_size & (UBIFS_BLOCK_SIZE - 1);
+	int offset = new_size & (UBIFS_BLOCK_SIZE - 1), budgeted = 1;
 	struct ubifs_inode *ui = ubifs_inode(inode);
 
 	dbg_gen("ino %lu, size %lld -> %lld", inode->i_ino, old_size, new_size);
@@ -811,8 +811,15 @@ static int do_truncation(struct ubifs_info *c, struct inode *inode,
 	/* A funny way to budget for truncation node */
 	req.dirtied_ino_d = UBIFS_TRUN_NODE_SZ;
 	err = ubifs_budget_space(c, &req);
-	if (err)
-		return err;
+	if (err) {
+		/*
+		 * Treat truncations to zero as deletion and always allow them,
+		 * just like we do for '->unlink()'.
+		 */
+		if (new_size || err != -ENOSPC)
+			return err;
+		budgeted = 0;
+	}
 
 	err = vmtruncate(inode, new_size);
 	if (err)
@@ -869,7 +876,12 @@ static int do_truncation(struct ubifs_info *c, struct inode *inode,
 	err = ubifs_jnl_truncate(c, inode, old_size, new_size);
 	mutex_unlock(&ui->ui_mutex);
 out_budg:
-	ubifs_release_budget(c, &req);
+	if (budgeted)
+		ubifs_release_budget(c, &req);
+	else {
+		c->nospace = c->nospace_rp = 0;
+		smp_wmb();
+	}
 	return err;
 }
 

fs/ubifs/find.c

@@ -211,14 +211,8 @@ static const struct ubifs_lprops *scan_for_dirty(struct ubifs_info *c,
  * dirty index heap, and it falls-back to LPT scanning if the heaps are empty
  * or do not have an LEB which satisfies the @min_space criteria.
  *
- * Note:
- *   o LEBs which have less than dead watermark of dirty space are never picked
- *   by this function;
- *
- * Returns zero and the LEB properties of
- * found dirty LEB in case of success, %-ENOSPC if no dirty LEB was found and a
- * negative error code in case of other failures. The returned LEB is marked as
- * "taken".
+ * Note, LEBs which have less than dead watermark of free + dirty space are
+ * never picked by this function.
  *
  * The additional @pick_free argument controls if this function has to return a
  * free or freeable LEB if one is present. For example, GC must to set it to %1,
@@ -231,6 +225,10 @@ static const struct ubifs_lprops *scan_for_dirty(struct ubifs_info *c,
  *
  * In addition @pick_free is set to %2 by the recovery process in order to
  * recover gc_lnum in which case an index LEB must not be returned.
+ *
+ * This function returns zero and the LEB properties of found dirty LEB in case
+ * of success, %-ENOSPC if no dirty LEB was found and a negative error code in
+ * case of other failures. The returned LEB is marked as "taken".
  */
 int ubifs_find_dirty_leb(struct ubifs_info *c, struct ubifs_lprops *ret_lp,
 			 int min_space, int pick_free)
@@ -245,7 +243,7 @@ int ubifs_find_dirty_leb(struct ubifs_info *c, struct ubifs_lprops *ret_lp,
 		int lebs, rsvd_idx_lebs = 0;
 
 		spin_lock(&c->space_lock);
-		lebs = c->lst.empty_lebs;
+		lebs = c->lst.empty_lebs + c->idx_gc_cnt;
 		lebs += c->freeable_cnt - c->lst.taken_empty_lebs;
 
 		/*
@@ -317,7 +315,7 @@ int ubifs_find_dirty_leb(struct ubifs_info *c, struct ubifs_lprops *ret_lp,
 		lp = idx_lp;
 
 	if (lp) {
-		ubifs_assert(lp->dirty >= c->dead_wm);
+		ubifs_assert(lp->free + lp->dirty >= c->dead_wm);
 		goto found;
 	}
 

fs/ubifs/gc.c

@@ -344,6 +344,12 @@ int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 		if (err)
 			goto out;
 
+		/* Allow for races with TNC */
+		c->gced_lnum = lnum;
+		smp_wmb();
+		c->gc_seq += 1;
+		smp_wmb();
+
 		if (c->gc_lnum == -1) {
 			c->gc_lnum = lnum;
 			err = LEB_RETAINED;

fs/ubifs/misc.h

@@ -283,38 +283,6 @@ static inline void *ubifs_idx_key(const struct ubifs_info *c,
 	return (void *)((struct ubifs_branch *)idx->branches)->key;
 }
 
-/**
- * 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, doubled because we always allow enough
- * space to write the index twice).
- *
- * Note, the calculation is pessimistic, which means that most of the time
- * UBIFS reports less space than it actually has.
- */
-static inline long long ubifs_reported_space(const struct ubifs_info *c,
-					     uint64_t free)
-{
-	int divisor, factor;
-
-	divisor = UBIFS_MAX_DATA_NODE_SZ + (c->max_idx_node_sz * 3);
-	factor = UBIFS_MAX_DATA_NODE_SZ - UBIFS_DATA_NODE_SZ;
-	do_div(free, divisor);
-
-	return free * factor;
-}
-
 /**
  * ubifs_current_time - round current time to time granularity.
  * @inode: inode
@@ -325,4 +293,21 @@ static inline struct timespec ubifs_current_time(struct inode *inode)
 		current_fs_time(inode->i_sb) : CURRENT_TIME_SEC;
 }
 
+/**
+ * ubifs_tnc_lookup - look up a file-system node.
+ * @c: UBIFS file-system description object
+ * @key: node key to lookup
+ * @node: the node is returned here
+ *
+ * This function look up and reads node with key @key. The caller has to make
+ * sure the @node buffer is large enough to fit the node. Returns zero in case
+ * of success, %-ENOENT if the node was not found, and a negative error code in
+ * case of failure.
+ */
+static inline int ubifs_tnc_lookup(struct ubifs_info *c,
+				   const union ubifs_key *key, void *node)
+{
+	return ubifs_tnc_locate(c, key, node, NULL, NULL);
+}
+
 #endif /* __UBIFS_MISC_H__ */

fs/ubifs/super.c

@@ -370,8 +370,9 @@ static int ubifs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct ubifs_info *c = dentry->d_sb->s_fs_info;
 	unsigned long long free;
+	__le32 *uuid = (__le32 *)c->uuid;
 
-	free = ubifs_budg_get_free_space(c);
+	free = ubifs_get_free_space(c);
 	dbg_gen("free space %lld bytes (%lld blocks)",
 		free, free >> UBIFS_BLOCK_SHIFT);
 
@@ -386,7 +387,8 @@ static int ubifs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_files = 0;
 	buf->f_ffree = 0;
 	buf->f_namelen = UBIFS_MAX_NLEN;
-
+	buf->f_fsid.val[0] = le32_to_cpu(uuid[0]) ^ le32_to_cpu(uuid[2]);
+	buf->f_fsid.val[1] = le32_to_cpu(uuid[1]) ^ le32_to_cpu(uuid[3]);
 	return 0;
 }
 
@@ -530,6 +532,12 @@ static int init_constants_early(struct ubifs_info *c)
 	c->dead_wm = ALIGN(MIN_WRITE_SZ, c->min_io_size);
 	c->dark_wm = ALIGN(UBIFS_MAX_NODE_SZ, c->min_io_size);
 
+	/*
+	 * Calculate how many bytes would be wasted at the end of LEB if it was
+	 * fully filled with data nodes of maximum size. This is used in
+	 * calculations when reporting free space.
+	 */
+	c->leb_overhead = c->leb_size % UBIFS_MAX_DATA_NODE_SZ;
 	return 0;
 }
 
@@ -647,13 +655,11 @@ static int init_constants_late(struct ubifs_info *c)
 	 * internally because it does not make much sense for UBIFS, but it is
 	 * necessary to report something for the 'statfs()' call.
 	 *
-	 * Subtract the LEB reserved for GC and the LEB which is reserved for
-	 * deletions.
-	 *
-	 * Review 'ubifs_calc_available()' if changing this calculation.
+	 * Subtract the LEB reserved for GC, the LEB which is reserved for
+	 * deletions, and assume only one journal head is available.
 	 */
-	tmp64 = c->main_lebs - 2;
-	tmp64 *= (uint64_t)c->leb_size - c->dark_wm;
+	tmp64 = c->main_lebs - 2 - c->jhead_cnt + 1;
+	tmp64 *= (uint64_t)c->leb_size - c->leb_overhead;
 	tmp64 = ubifs_reported_space(c, tmp64);
 	c->block_cnt = tmp64 >> UBIFS_BLOCK_SHIFT;