From: Bruno Faccini <bruno.faccini@xxxxxxxxx>
I have first found this way to fix holes in previous ext4 layers versions
where an array of struct ext4_ext_path had been allocated with an arbitrary
evaluated size and finally could overrun upon ext_depth() growth outside
i_data_sem protection. But it seems it can still help with recent ext4
version, to avoid re-allocation need and overhead when it can be allocated
to max possible extent depth (ie, 5 presently) at first time and for a low
cost regarding its memory foot-print, it should also avoid further invalid
dereference by underlying callers sharing same ppath (with present
inter-routines path re-use scheme), and also upon re-allocation error.
Signed-off-by: Bruno Faccini <bruno.faccini@xxxxxxxxx>
---
fs/ext4/ext4.h | 3 +
fs/ext4/extents.c | 113 ++++++++++++++++++++++++++--------------
fs/ext4/move_extent.c | 10 +--
fs/ext4/super.c | 3 -
4 files changed, 85 insertions(+), 44 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 1e20fa9..73d5866 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1340,6 +1340,9 @@ struct ext4_sb_info {
unsigned long s_ext_extents;
#endif
+ /* maximum possible extents tree depth, to be computed at mount time */
+ unsigned int s_max_ext_tree_depth;
+
/* for buddy allocator */
struct ext4_group_info ***s_group_info;
struct inode *s_buddy_cache;
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index b52fea3..aee676d 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -871,19 +871,18 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,
if (path) {
ext4_ext_drop_refs(path);
- if (depth > path[0].p_maxdepth) {
- kfree(path);
- *orig_path = path = NULL;
- }
- }
- if (!path) {
+ /* path has been allocated for the max possible depth
+ * so we can simply reuse it */
+ /* XXX need to clear/zero old path content? */
+ } else {
/* account possible depth increase */
- path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
+ path = kzalloc(sizeof(struct ext4_ext_path) *
+ EXT4_SB(inode->i_sb)->s_max_ext_tree_depth,
GFP_NOFS);
if (unlikely(!path))
return ERR_PTR(-ENOMEM);
- path[0].p_maxdepth = depth + 1;
}
+ path[0].p_maxdepth = depth + 1;
path[0].p_hdr = eh;
path[0].p_bh = NULL;
@@ -934,9 +933,11 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,
err:
ext4_ext_drop_refs(path);
- kfree(path);
- if (orig_path)
- *orig_path = NULL;
+
+ /* do not free *orig_path, it is likely to be referenced by callers */
+ if (!orig_path)
+ kfree(path);
+
return ERR_PTR(ret);
}
@@ -2147,7 +2148,8 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
ext4_lblk_t block, ext4_lblk_t num,
struct fiemap_extent_info *fieinfo)
{
- struct ext4_ext_path *path = NULL;
+ struct ext4_ext_path *path = NULL, *orig_path = NULL;
+ struct ext4_ext_path **orig_ppath = &orig_path;
struct ext4_extent *ex;
struct extent_status es;
ext4_lblk_t next, next_del, start = 0, end = 0;
@@ -2161,13 +2163,16 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
/* find extent for this block */
down_read(&EXT4_I(inode)->i_data_sem);
- path = ext4_find_extent(inode, block, &path, 0);
+ path = ext4_find_extent(inode, block, orig_ppath, 0);
if (IS_ERR(path)) {
up_read(&EXT4_I(inode)->i_data_sem);
err = PTR_ERR(path);
path = NULL;
break;
}
+ if (!orig_path)
+ orig_path = path;
+ /* XXX else BUG_ON(path != orig_path); */
depth = ext_depth(inode);
if (unlikely(path[depth].p_hdr == NULL)) {
@@ -2287,8 +2292,8 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
block = es.es_lblk + es.es_len;
}
- ext4_ext_drop_refs(path);
- kfree(path);
+ ext4_ext_drop_refs(orig_path);
+ kfree(orig_path);
return err;
}
@@ -2910,7 +2915,8 @@ again:
path[k].p_block =
le16_to_cpu(path[k].p_hdr->eh_entries)+1;
} else {
- path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1),
+ path = kzalloc(sizeof(struct ext4_ext_path) *
+ EXT4_SB(inode->i_sb)->s_max_ext_tree_depth,
GFP_NOFS);
if (path == NULL) {
ext4_journal_stop(handle);
@@ -3051,13 +3057,14 @@ out:
*/
void ext4_ext_init(struct super_block *sb)
{
+ ext4_fsblk_t maxblocks;
+
/*
* possible initialization would be here
*/
if (ext4_has_feature_extents(sb)) {
-#if defined(AGGRESSIVE_TEST) || defined(CHECK_BINSEARCH) || defined(EXTENTS_STATS)
- printk(KERN_INFO "EXT4-fs: file extents enabled"
+ printk(KERN_INFO "EXT4-fs (%s): file extents enabled"
#ifdef AGGRESSIVE_TEST
", aggressive tests"
#endif
@@ -3067,8 +3074,36 @@ void ext4_ext_init(struct super_block *sb)
#ifdef EXTENTS_STATS
", stats"
#endif
- "\n");
+ , sb->s_id);
+
+
+ EXT4_SB(sb)->s_max_ext_tree_depth = 1;
+
+ maxblocks = sb->s_maxbytes / sb->s_blocksize;
+
+ /* 1st/root level/node of extents tree stands in i_data and
+ * entries stored in tree nodes can be of type ext4_extent
+ * (leaf node) or ext4_extent_idx (internal node) */
+ maxblocks /= (sizeof(((struct ext4_inode_info *)0x0)->i_data) -
+ sizeof(struct ext4_extent_header)) /
+ max(sizeof(struct ext4_extent),
+ sizeof(struct ext4_extent_idx));
+
+ /* compute maximum extents tree depth for a fully populated
+ * file of max size made of only minimal/1-block extents */
+ while (maxblocks > 0) {
+ maxblocks /= (sb->s_blocksize -
+ sizeof(struct ext4_extent_header)) /
+ max(sizeof(struct ext4_extent),
+ sizeof(struct ext4_extent_idx));
+ EXT4_SB(sb)->s_max_ext_tree_depth++;
+ }
+
+#ifdef EXT_DEBUG
+ printk(", maximum tree depth=%u",
+ EXT4_SB(sb)->s_max_ext_tree_depth);
#endif
+ printk("\n");
#ifdef EXTENTS_STATS
spin_lock_init(&EXT4_SB(sb)->s_ext_stats_lock);
EXT4_SB(sb)->s_ext_min = 1 << 30;
@@ -5348,18 +5383,18 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
ext4_lblk_t start, ext4_lblk_t shift,
enum SHIFT_DIRECTION SHIFT)
{
- struct ext4_ext_path *path;
+ struct ext4_ext_path *path, *orig_path;
int ret = 0, depth;
struct ext4_extent *extent;
ext4_lblk_t stop, *iterator, ex_start, ex_end;
/* Let path point to the last extent */
- path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
- if (IS_ERR(path))
- return PTR_ERR(path);
+ orig_path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
+ if (IS_ERR(orig_path))
+ return PTR_ERR(orig_path);
- depth = path->p_depth;
- extent = path[depth].p_ext;
+ depth = orig_path->p_depth;
+ extent = orig_path[depth].p_ext;
if (!extent)
goto out;
@@ -5371,9 +5406,11 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
* sure the hole is big enough to accommodate the shift.
*/
if (SHIFT == SHIFT_LEFT) {
- path = ext4_find_extent(inode, start - 1, &path, 0);
- if (IS_ERR(path))
- return PTR_ERR(path);
+ path = ext4_find_extent(inode, start - 1, &orig_path, 0);
+ if (IS_ERR(path)) {
+ ret = PTR_ERR(path);
+ goto out;
+ }
depth = path->p_depth;
extent = path[depth].p_ext;
if (extent) {
@@ -5387,9 +5424,8 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
if ((start == ex_start && shift > ex_start) ||
(shift > start - ex_end)) {
- ext4_ext_drop_refs(path);
- kfree(path);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
}
@@ -5405,15 +5441,18 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
/* Its safe to start updating extents */
while (start < stop) {
- path = ext4_find_extent(inode, *iterator, &path, 0);
- if (IS_ERR(path))
- return PTR_ERR(path);
+ path = ext4_find_extent(inode, *iterator, &orig_path, 0);
+ if (IS_ERR(path)) {
+ ret = PTR_ERR(path);
+ goto out;
+ }
depth = path->p_depth;
extent = path[depth].p_ext;
if (!extent) {
EXT4_ERROR_INODE(inode, "unexpected hole at %lu",
(unsigned long) *iterator);
- return -EFSCORRUPTED;
+ ret = -EFSCORRUPTED;
+ goto out;
}
if (SHIFT == SHIFT_LEFT && *iterator >
le32_to_cpu(extent->ee_block)) {
@@ -5445,8 +5484,8 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
break;
}
out:
- ext4_ext_drop_refs(path);
- kfree(path);
+ ext4_ext_drop_refs(orig_path);
+ kfree(orig_path);
return ret;
}
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index fb6f117..7c319c5 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -39,13 +39,11 @@ get_ext_path(struct inode *inode, ext4_lblk_t lblock,
path = ext4_find_extent(inode, lblock, ppath, EXT4_EX_NOCACHE);
if (IS_ERR(path))
return PTR_ERR(path);
- if (path[ext_depth(inode)].p_ext == NULL) {
- ext4_ext_drop_refs(path);
- kfree(path);
- *ppath = NULL;
+ if (path[ext_depth(inode)].p_ext == NULL)
return -ENODATA;
- }
- *ppath = path;
+ if (*ppath == NULL)
+ *ppath = path;
+ /* XXX else BUG_ON(path != *ppath); */
return 0;
}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 486e869..199157a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3701,6 +3701,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
goto failed_mount3a;
+ ext4_ext_init(sb); /* needed before using extent-mapped journal */
+
/*
* The first inode we look at is the journal inode. Don't try
* root first: it may be modified in the journal!
@@ -3894,7 +3896,6 @@ no_journal:
goto failed_mount4a;
}
- ext4_ext_init(sb);
err = ext4_mb_init(sb);
if (err) {
ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
--
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