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Message-ID: <20140831194830.GH8974@thunk.org>
Date: Sun, 31 Aug 2014 15:48:30 -0400
From: Theodore Ts'o <tytso@....edu>
To: Dmitry Monakhov <dmonakhov@...nvz.org>
Cc: linux-ext4@...r.kernel.org, lczerner@...hat.com
Subject: Re: [PATCH 2/2] ext4: refactor ext4_move_extents code base v5
On Sat, Aug 16, 2014 at 05:17:06PM +0400, Dmitry Monakhov wrote:
> ext4_move_extents is too complex for review. It has duplicate almost each function
> available in the rest of other codebase. It has useless artificial restriction
> orig_offset == donor_offset. But in fact logic of ext4_move_extents
> is very simple:
>
> Iterate extents one by one (similar to ext4_fill_fiemap_extents)
> ->Iterate each page covered extent (similar to generic_perform_write)
> ->swap extents for covered by page (can be shared with IOC_MOVE_DATA)
Applied, thanks. I applied a clean up patch to fix up some issues I
found, the most significant was that if ext4_ext_find_extent() return
an error, it could potentially cause a kernel OOPS.
- Ted
>From 06d9961c15245961c90eab3e5f08307866a4b1d8 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@....edu>
Date: Sun, 31 Aug 2014 15:03:14 -0400
Subject: [PATCH] ext4: fix ext4_swap_extents() error handling
If ext4_ext_find_extent() returns an error, we have to clear path1 or
path2 or else we would end up trying to free an ERR_PTR, which would
be bad.
Also eliminate some redundant code and mark the error paths as unlikely()
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
fs/ext4/extents.c | 62 ++++++++++++++++++++++++++-----------------------------
1 file changed, 29 insertions(+), 33 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8555940..bc3b49f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -862,7 +862,7 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
if (!path) {
path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
GFP_NOFS);
- if (!path)
+ if (unlikely(!path))
return ERR_PTR(-ENOMEM);
alloc = 1;
}
@@ -882,7 +882,7 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
bh = read_extent_tree_block(inode, path[ppos].p_block, --i,
flags);
- if (IS_ERR(bh)) {
+ if (unlikely(IS_ERR(bh))) {
ret = PTR_ERR(bh);
goto err;
}
@@ -5551,10 +5551,10 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
BUG_ON(!mutex_is_locked(&inode1->i_mutex));
*erp = ext4_es_remove_extent(inode1, lblk1, count);
- if (*erp)
+ if (unlikely(*erp))
return 0;
*erp = ext4_es_remove_extent(inode2, lblk2, count);
- if (*erp)
+ if (unlikely(*erp))
return 0;
while (count) {
@@ -5564,20 +5564,24 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
int split = 0;
path1 = ext4_ext_find_extent(inode1, lblk1, NULL, EXT4_EX_NOCACHE);
- if (IS_ERR(path1)) {
+ if (unlikely(IS_ERR(path1))) {
*erp = PTR_ERR(path1);
- break;
+ path1 = NULL;
+ finish:
+ count = 0;
+ goto repeat;
}
path2 = ext4_ext_find_extent(inode2, lblk2, NULL, EXT4_EX_NOCACHE);
- if (IS_ERR(path2)) {
+ if (unlikely(IS_ERR(path2))) {
*erp = PTR_ERR(path2);
- break;
+ path2 = NULL;
+ goto finish;
}
ex1 = path1[path1->p_depth].p_ext;
ex2 = path2[path2->p_depth].p_ext;
/* Do we have somthing to swap ? */
if (unlikely(!ex2 || !ex1))
- break;
+ goto finish;
e1_blk = le32_to_cpu(ex1->ee_block);
e2_blk = le32_to_cpu(ex2->ee_block);
@@ -5599,7 +5603,7 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
next2 = e1_blk;
/* Do we have something to swap */
if (next1 == EXT_MAX_BLOCKS || next2 == EXT_MAX_BLOCKS)
- break;
+ goto finish;
/* Move to the rightest boundary */
len = next1 - lblk1;
if (len < next2 - lblk2)
@@ -5617,15 +5621,15 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
split = 1;
*erp = ext4_force_split_extent_at(handle, inode1,
path1, lblk1, 0);
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
}
if (e2_blk < lblk2) {
split = 1;
*erp = ext4_force_split_extent_at(handle, inode2,
path2, lblk2, 0);
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
}
/* ext4_split_extent_at() may retult in leaf extent split,
* path must to be revalidated. */
@@ -5643,15 +5647,15 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
split = 1;
*erp = ext4_force_split_extent_at(handle, inode1,
path1, lblk1 + len, 0);
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
}
if (len != e2_len) {
split = 1;
*erp = ext4_force_split_extent_at(handle, inode2,
path2, lblk2 + len, 0);
if (*erp)
- break;
+ goto finish;
}
/* ext4_split_extent_at() may retult in leaf extent split,
* path must to be revalidated. */
@@ -5660,11 +5664,11 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
BUG_ON(e2_len != e1_len);
*erp = ext4_ext_get_access(handle, inode1, path1 + path1->p_depth);
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
*erp = ext4_ext_get_access(handle, inode2, path2 + path2->p_depth);
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
/* Both extents are fully inside boundaries. Swap it now */
tmp_ex = *ex1;
@@ -5681,8 +5685,8 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
ext4_ext_try_to_merge(handle, inode1, path1, ex1);
*erp = ext4_ext_dirty(handle, inode2, path2 +
path2->p_depth);
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
*erp = ext4_ext_dirty(handle, inode1, path1 +
path1->p_depth);
/*
@@ -5691,8 +5695,8 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
* only due to journal error, so full transaction will be
* aborted anyway.
*/
- if (*erp)
- break;
+ if (unlikely(*erp))
+ goto finish;
lblk1 += len;
lblk2 += len;
replaced_count += len;
@@ -5710,13 +5714,5 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
path2 = NULL;
}
}
- if (path1) {
- ext4_ext_drop_refs(path1);
- kfree(path1);
- }
- if (path2) {
- ext4_ext_drop_refs(path2);
- kfree(path2);
- }
return replaced_count;
}
--
2.1.0
--
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