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Date: Thu, 4 Jan 2007 14:24:07 +0530
From: "Amit K. Arora" <aarora@...ux.vnet.ibm.com>
To: Mingming Cao <cmm@...ibm.com>
Cc: linux-ext4@...r.kernel.org, suparna@...ibm.com, alex@...sterfs.com
Subject: Re: [PATCH 1/1 version2] Extent overlap bugfix in ext4
On Wed, Jan 03, 2007 at 11:36:01AM +0530, Amit K. Arora wrote:
> >
> > > + b2 = ext4_ext_next_allocated_block(path);
> > > + if (b2 == EXT_MAX_BLOCK)
> > > +
> > > return NULL;
> > > + path = ext4_ext_find_extent(inode, b2, path);
> > > + if (IS_ERR(path))
> > > + return NULL;
> > > + BUG_ON(path[depth].p_hdr == NULL);
> > > + ex = path[depth].p_ext;
> > > +
> >
> > How useful to have the next extent pointer?It seems only used to print
> > out warning messages. I am a little concerned about the expensive
> > ext4_ext_find_extent(). After all ext4_ext_next_allocated_block()
> > already returns the start block of next extent, isn't it?
>
> Ok, agreed. Will get rid of this extra code.
Here is the new patch. Please review.
Thanks!
Signed-off-by: Amit Arora <aarora@...ibm.com>
---
fs/ext4/extents.c | 71 ++++++++++++++++++++++++++++++++++++++--
include/linux/ext4_fs_extents.h | 1
2 files changed, 70 insertions(+), 2 deletions(-)
Index: linux-2.6.19.prealloc/fs/ext4/extents.c
===================================================================
--- linux-2.6.19.prealloc.orig/fs/ext4/extents.c
+++ linux-2.6.19.prealloc/fs/ext4/extents.c
@@ -1119,6 +1119,45 @@ ext4_can_extents_be_merged(struct inode
}
/*
+ * ext4_ext_check_overlap:
+ * check if a portion of the "newext" extent overlaps with an
+ * existing extent.
+ *
+ * Returns 1 if it finds an extent which may overlap with the
+ * new extent, and puts the logical block number of the first block
+ * of this extent at a location pointed by the "block" argument.
+ * If there is no such extent, it returns 0.
+ * Returns errno, incase of an error.
+ */
+int ext4_ext_check_overlap(struct inode *inode,
+ struct ext4_extent *newext,
+ unsigned long *block)
+{
+ struct ext4_ext_path *path;
+ unsigned int depth, b1, len1;
+ int ret = 0;
+
+ b1 = le32_to_cpu(newext->ee_block);
+ len1 = le16_to_cpu(newext->ee_len);
+ path = ext4_ext_find_extent(inode, b1, NULL);
+ if (IS_ERR(path)) {
+ ret = PTR_ERR(path);
+ goto out;
+ }
+ depth = ext_depth(inode);
+ BUG_ON(path[depth].p_ext == NULL && depth != 0);
+
+ *block = ext4_ext_next_allocated_block(path);
+ if (*block == EXT_MAX_BLOCK)
+ goto out;
+
+ if (b1 + len1 > *block)
+ ret = 1;
+out:
+ return ret;
+}
+
+/*
* ext4_ext_insert_extent:
* tries to merge requsted extent into the existing extent or
* inserts requested extent as new one into the tree,
@@ -1133,12 +1172,25 @@ int ext4_ext_insert_extent(handle_t *han
struct ext4_extent *nearex; /* nearest extent */
struct ext4_ext_path *npath = NULL;
int depth, len, err, next;
+ unsigned long oblock;
BUG_ON(newext->ee_len == 0);
depth = ext_depth(inode);
ex = path[depth].p_ext;
BUG_ON(path[depth].p_hdr == NULL);
+ /* check for overlap */
+ err = ext4_ext_check_overlap(inode, newext, &oblock);
+ if (err > 0) {
+ printk(KERN_ERR "ERROR: newext=%u/%u overlaps with an "
+ "existing extent, which starts with %lu\n",
+ le32_to_cpu(newext->ee_block),
+ le16_to_cpu(newext->ee_len),
+ oblock);
+ ext4_ext_show_leaf(inode, path);
+ BUG();
+ }
+
/* try to insert block into found extent and return */
if (ex && ext4_can_extents_be_merged(inode, ex, newext)) {
ext_debug("append %d block to %d:%d (from %llu)\n",
@@ -1984,6 +2036,10 @@ int ext4_ext_get_blocks(handle_t *handle
*/
if (ee_len > EXT_MAX_LEN)
goto out2;
+
+ if (iblock < ee_block && iblock + max_blocks >= ee_block)
+ allocated = ee_block - iblock;
+
/* if found extent covers block, simply return it */
if (iblock >= ee_block && iblock < ee_block + ee_len) {
newblock = iblock - ee_block + ee_start;
@@ -2016,7 +2072,19 @@ int ext4_ext_get_blocks(handle_t *handle
/* allocate new block */
goal = ext4_ext_find_goal(inode, path, iblock);
- allocated = max_blocks;
+
+ /* Check if we can really insert (iblock)::(iblock+max_blocks) extent */
+ newex.ee_block = cpu_to_le32(iblock);
+ if (!allocated) {
+ newex.ee_len = cpu_to_le16(max_blocks);
+ err = ext4_ext_check_overlap(inode, &newex, &allocated);
+ if (err < 0)
+ goto out2;
+ else if (!err)
+ allocated = max_blocks;
+ else
+ allocated = allocated - iblock;
+ }
newblock = ext4_new_blocks(handle, inode, goal, &allocated, &err);
if (!newblock)
goto out2;
@@ -2024,7 +2092,6 @@ int ext4_ext_get_blocks(handle_t *handle
goal, newblock, allocated);
/* try to insert new extent into found leaf and return */
- newex.ee_block = cpu_to_le32(iblock);
ext4_ext_store_pblock(&newex, newblock);
newex.ee_len = cpu_to_le16(allocated);
err = ext4_ext_insert_extent(handle, inode, path, &newex);
Index: linux-2.6.19.prealloc/include/linux/ext4_fs_extents.h
===================================================================
--- linux-2.6.19.prealloc.orig/include/linux/ext4_fs_extents.h
+++ linux-2.6.19.prealloc/include/linux/ext4_fs_extents.h
@@ -190,6 +190,7 @@ ext4_ext_invalidate_cache(struct inode *
extern int ext4_extent_tree_init(handle_t *, struct inode *);
extern int ext4_ext_calc_credits_for_insert(struct inode *, struct ext4_ext_path *);
+extern int ext4_ext_check_overlap(struct inode *, struct ext4_extent *, unsigned long *);
extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *);
extern int ext4_ext_walk_space(struct inode *, unsigned long, unsigned long, ext_prepare_callback, void *);
extern struct ext4_ext_path * ext4_ext_find_extent(struct inode *, int, struct ext4_ext_path *);
--
Regards,
Amit Arora
-
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