From 032d8f7268444a0f5d4ee02d9513d682d5b8edfc Mon Sep 17 00:00:00 2001 From: Joern Engel Date: Tue, 13 Apr 2010 17:46:37 +0200 Subject: [PATCH] [LogFS] Prevent memory corruption on large deletes Removing sufficiently large files would create aliases for a large number of segments. This in turn results in a large number of journal entries and an overflow of s_je_array. Cheap fix is to add a BUG_ON, turning memory corruption into something annoying, but less dangerous. Real fix is to count the number of affected segments and prevent the problem completely. Signed-off-by: Joern Engel --- fs/logfs/gc.c | 8 ++++++++ fs/logfs/journal.c | 3 +++ fs/logfs/logfs.h | 8 +++++++- fs/logfs/readwrite.c | 14 ++++++++++++++ fs/logfs/super.c | 2 ++ 5 files changed, 34 insertions(+), 1 deletion(-) diff --git a/fs/logfs/gc.c b/fs/logfs/gc.c index 92949f95a901..e8253e7fb6b2 100644 --- a/fs/logfs/gc.c +++ b/fs/logfs/gc.c @@ -458,6 +458,14 @@ static void __logfs_gc_pass(struct super_block *sb, int target) struct logfs_block *block; int round, progress, last_progress = 0; + /* + * Doing too many changes to the segfile at once would result + * in a large number of aliases. Write the journal before + * things get out of hand. + */ + if (super->s_shadow_tree.no_shadowed_segments >= MAX_OBJ_ALIASES) + logfs_write_anchor(sb); + if (no_free_segments(sb) >= target && super->s_no_object_aliases < MAX_OBJ_ALIASES) return; diff --git a/fs/logfs/journal.c b/fs/logfs/journal.c index d57c7b07b60b..2c22a4ad5329 100644 --- a/fs/logfs/journal.c +++ b/fs/logfs/journal.c @@ -493,6 +493,8 @@ static void account_shadows(struct super_block *sb) btree_grim_visitor64(&tree->new, (unsigned long)sb, account_shadow); btree_grim_visitor64(&tree->old, (unsigned long)sb, account_shadow); + btree_grim_visitor32(&tree->segment_map, 0, NULL); + tree->no_shadowed_segments = 0; if (li->li_block) { /* @@ -660,6 +662,7 @@ static int logfs_write_je_buf(struct super_block *sb, void *buf, u16 type, if (ofs < 0) return ofs; logfs_buf_write(area, ofs, super->s_compressed_je, len); + BUG_ON(super->s_no_je >= MAX_JOURNAL_ENTRIES); super->s_je_array[super->s_no_je++] = cpu_to_be64(ofs); return 0; } diff --git a/fs/logfs/logfs.h b/fs/logfs/logfs.h index 97195b9e93a5..c9929eed80b1 100644 --- a/fs/logfs/logfs.h +++ b/fs/logfs/logfs.h @@ -257,10 +257,14 @@ struct logfs_shadow { * struct shadow_tree * @new: shadows where old_ofs==0, indexed by new_ofs * @old: shadows where old_ofs!=0, indexed by old_ofs + * @segment_map: bitfield of segments containing shadows + * @no_shadowed_segment: number of segments containing shadows */ struct shadow_tree { struct btree_head64 new; struct btree_head64 old; + struct btree_head32 segment_map; + int no_shadowed_segments; }; struct object_alias_item { @@ -311,6 +315,8 @@ struct logfs_block_ops { write_alias_t *write_one_alias); }; +#define MAX_JOURNAL_ENTRIES 256 + struct logfs_super { struct mtd_info *s_mtd; /* underlying device */ struct block_device *s_bdev; /* underlying device */ @@ -377,7 +383,7 @@ struct logfs_super { u32 s_journal_ec[LOGFS_JOURNAL_SEGS]; /* journal erasecounts */ u64 s_last_version; struct logfs_area *s_journal_area; /* open journal segment */ - __be64 s_je_array[64]; + __be64 s_je_array[MAX_JOURNAL_ENTRIES]; int s_no_je; int s_sum_index; /* for the 12 summaries */ diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c index 3659c37fbd72..7e0c39c49719 100644 --- a/fs/logfs/readwrite.c +++ b/fs/logfs/readwrite.c @@ -1219,6 +1219,18 @@ static void free_shadow(struct inode *inode, struct logfs_shadow *shadow) mempool_free(shadow, super->s_shadow_pool); } +static void mark_segment(struct shadow_tree *tree, u32 segno) +{ + int err; + + if (!btree_lookup32(&tree->segment_map, segno)) { + err = btree_insert32(&tree->segment_map, segno, (void *)1, + GFP_NOFS); + BUG_ON(err); + tree->no_shadowed_segments++; + } +} + /** * fill_shadow_tree - Propagate shadow tree changes due to a write * @inode: Inode owning the page @@ -1266,6 +1278,8 @@ static void fill_shadow_tree(struct inode *inode, struct page *page, super->s_dirty_used_bytes += shadow->new_len; super->s_dirty_free_bytes += shadow->old_len; + mark_segment(tree, shadow->old_ofs >> super->s_segshift); + mark_segment(tree, shadow->new_ofs >> super->s_segshift); } } diff --git a/fs/logfs/super.c b/fs/logfs/super.c index 9d856c49afc5..d6e1f4fc3115 100644 --- a/fs/logfs/super.c +++ b/fs/logfs/super.c @@ -451,6 +451,8 @@ static int logfs_read_sb(struct super_block *sb, int read_only) btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool); btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool); + btree_init_mempool32(&super->s_shadow_tree.segment_map, + super->s_btree_pool); ret = logfs_init_mapping(sb); if (ret) -- 2.20.1