From: Artem Bityutskiy Date: Wed, 3 Sep 2008 13:17:14 +0000 (+0300) Subject: UBIFS: fix division by zero X-Git-Tag: v2.6.27-rc6~7^2~1 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f171d4d769c8ccac6675892960e37f6485837fae;p=linux-2.6 UBIFS: fix division by zero If fanout is 3, we have division by zero in 'ubifs_read_superblock()': divide error: 0000 [#1] PREEMPT SMP Pid: 28744, comm: mount Not tainted (2.6.27-rc4-ubifs-2.6 #23) EIP: 0060:[] EFLAGS: 00010202 CPU: 0 EIP is at ubifs_reported_space+0x2d/0x69 [ubifs] EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000 ESI: 00000000 EDI: f0ae64b0 EBP: f1f9fcf4 ESP: f1f9fce0 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 Signed-off-by: Artem Bityutskiy --- diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c index 101d278c59..73db464cd0 100644 --- a/fs/ubifs/budget.c +++ b/fs/ubifs/budget.c @@ -723,24 +723,25 @@ void ubifs_release_dirty_inode_budget(struct ubifs_info *c, */ long long ubifs_reported_space(const struct ubifs_info *c, uint64_t 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 * 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;