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Commit 032d8f72 authored by Joern Engel's avatar Joern Engel
Browse files

[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: default avatarJoern Engel <joern@logfs.org>
parent e05c378f

fs/logfs/gc.c

+8 −0
Original line number Diff line number Diff line
@@ -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;

fs/logfs/journal.c

+3 −0
Original line number Diff line number Diff line
@@ -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;

}

fs/logfs/logfs.h

+7 −1
Original line number Diff line number Diff line
@@ -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 */

fs/logfs/readwrite.c

+14 −0
Original line number Diff line number Diff line
@@ -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);

	}

}

fs/logfs/super.c

+2 −0
Original line number Diff line number Diff line
@@ -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)