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Date: Mon, 24 Nov 2008 16:45:53 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: Theodore Tso <tytso@....EDU>
Cc: cmm@...ibm.com, sandeen@...hat.com, linux-ext4@...r.kernel.org
Subject: Re: [PATCH -V2 5/5] ext4: Fix the race between read_inode_bitmap
and ext4_new_inode
On Sun, Nov 23, 2008 at 11:05:24PM -0500, Theodore Tso wrote:
> On Fri, Nov 21, 2008 at 10:14:35PM +0530, Aneesh Kumar K.V wrote:
> > We need to make sure we update the inode bitmap and clear
> > EXT4_BG_INODE_UNINIT flag with sb_bgl_lock held. We look
> > at EXT4_BG_INODE_UNINIT and reinit the inode bitmap each
> > time in ext4_read_inode_bitmap (introduced by
> > c806e68f5647109350ec546fee5b526962970fd2 )
>
> OK, I believe I've checked in all of your patches in this series into
> the ext4 patch queue
>
> Some of them have comments that still need to be cleared; this one in
> particular needs a better commit comment, and ideally a comment for
> the new function ext4_claim_inode().
I will add a comment to the above function.
>
> Also, please don't rename variables unnecessarily; if you really think
> it's needed, please do so in a separate patch. The renaming of
> variables makes it much harder to review the patch, since it bloats
> the patch, and obscures the true changes happening in the patch.
> Please explain why you are making some of the changes you made in the
> patch. In particular, why does it matter the order in which you
> unlock the bh and sb_bgl_lock in balloc.c, mballoc.c and inode.c?
>
>
I will put the variable name cleanup and unlock cleanup into separate
patch. The unlock is done as a cleanup so that unlock appears in the
reverse order with which we did locking. It doesn't make any difference.
-aneesh
Updated patch below
ext4: Fix the race between read_inode_bitmap() and ext4_new_inode()
From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
We need to make sure we update the inode bitmap and clear
EXT4_BG_INODE_UNINIT flag with sb_bgl_lock held. We look
at EXT4_BG_INODE_UNINIT and reinit the inode bitmap each
time in ext4_read_inode_bitmap (introduced by
c806e68f5647109350ec546fee5b526962970fd2 )
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
fs/ext4/ialloc.c | 146 ++++++++++++++++++++++++++++++++----------------------
1 files changed, 86 insertions(+), 60 deletions(-)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 229708b..d1ccae5 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -573,6 +573,79 @@ static int find_group_other(struct super_block *sb, struct inode *parent,
}
/*
+ * claim the inode from the inode bitmap. If the group
+ * is uninit we need to take the groups's sb_bgl_lock
+ * and clear the uninit flag. The inode bitmap update
+ * and group desc uninit flag clear should be done
+ * after holding sb_bgl_lock so that ext4_read_inode_bitmap
+ * doesn't race with the ext4_claim_inode
+ */
+static int ext4_claim_inode(struct super_block *sb,
+ struct buffer_head *inode_bitmap_bh,
+ unsigned long ino, ext4_group_t group, int mode)
+{
+ int free = 0, retval = 0, count;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group, NULL);
+
+ spin_lock(sb_bgl_lock(sbi, group));
+ if (ext4_set_bit(ino, inode_bitmap_bh->b_data)) {
+ /* not a free inode */
+ retval = 1;
+ goto err_ret;
+ }
+ ino++;
+ if ((group == 0 && ino < EXT4_FIRST_INO(sb)) ||
+ ino > EXT4_INODES_PER_GROUP(sb)) {
+ spin_unlock(sb_bgl_lock(sbi, group));
+ ext4_error(sb, __func__,
+ "reserved inode or inode > inodes count - "
+ "block_group = %u, inode=%lu", group,
+ ino + group * EXT4_INODES_PER_GROUP(sb));
+ return 1;
+ }
+ /* If we didn't allocate from within the initialized part of the inode
+ * table then we need to initialize up to this inode. */
+ if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+
+ if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
+ gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
+ /* When marking the block group with
+ * ~EXT4_BG_INODE_UNINIT we don't want to depend
+ * on the value of bg_itable_unused even though
+ * mke2fs could have initialized the same for us.
+ * Instead we calculated the value below
+ */
+
+ free = 0;
+ } else {
+ free = EXT4_INODES_PER_GROUP(sb) -
+ ext4_itable_unused_count(sb, gdp);
+ }
+
+ /*
+ * Check the relative inode number against the last used
+ * relative inode number in this group. if it is greater
+ * we need to update the bg_itable_unused count
+ *
+ */
+ if (ino > free)
+ ext4_itable_unused_set(sb, gdp,
+ (EXT4_INODES_PER_GROUP(sb) - ino));
+ }
+ count = ext4_free_inodes_count(sb, gdp) - 1;
+ ext4_free_inodes_set(sb, gdp, count);
+ if (S_ISDIR(mode)) {
+ count = ext4_used_dirs_count(sb, gdp) + 1;
+ ext4_used_dirs_set(sb, gdp, count);
+ }
+ gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
+err_ret:
+ spin_unlock(sb_bgl_lock(sbi, group));
+ return retval;
+}
+
+/*
* There are two policies for allocating an inode. If the new inode is
* a directory, then a forward search is made for a block group with both
* free space and a low directory-to-inode ratio; if that fails, then of
@@ -594,7 +667,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
struct ext4_super_block *es;
struct ext4_inode_info *ei;
struct ext4_sb_info *sbi;
- int ret2, err = 0, count;
+ int ret2, err = 0;
struct inode *ret;
ext4_group_t i;
int free = 0;
@@ -657,8 +730,13 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
if (err)
goto fail;
- if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group),
- ino, inode_bitmap_bh->b_data)) {
+ BUFFER_TRACE(group_desc_bh, "get_write_access");
+ err = ext4_journal_get_write_access(handle,
+ group_desc_bh);
+ if (err)
+ goto fail;
+ if (!ext4_claim_inode(sb, inode_bitmap_bh,
+ ino, group, mode)) {
/* we won it */
BUFFER_TRACE(inode_bitmap_bh,
"call ext4_journal_dirty_metadata");
@@ -666,10 +744,13 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
inode_bitmap_bh);
if (err)
goto fail;
+ /* zero bit is inode number 1*/
+ ino++;
goto got;
}
/* we lost it */
jbd2_journal_release_buffer(handle, inode_bitmap_bh);
+ jbd2_journal_release_buffer(handle, group_desc_bh);
if (++ino < EXT4_INODES_PER_GROUP(sb))
goto repeat_in_this_group;
@@ -689,22 +770,6 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
goto out;
got:
- ino++;
- if ((group == 0 && ino < EXT4_FIRST_INO(sb)) ||
- ino > EXT4_INODES_PER_GROUP(sb)) {
- ext4_error(sb, __func__,
- "reserved inode or inode > inodes count - "
- "block_group = %u, inode=%lu", group,
- ino + group * EXT4_INODES_PER_GROUP(sb));
- err = -EIO;
- goto fail;
- }
-
- BUFFER_TRACE(group_desc_bh, "get_write_access");
- err = ext4_journal_get_write_access(handle, group_desc_bh);
- if (err)
- goto fail;
-
/* We may have to initialize the block bitmap if it isn't already */
if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
@@ -741,49 +806,10 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
if (err)
goto fail;
}
-
- spin_lock(sb_bgl_lock(sbi, group));
- /* If we didn't allocate from within the initialized part of the inode
- * table then we need to initialize up to this inode. */
- if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
- if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
- gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
-
- /* When marking the block group with
- * ~EXT4_BG_INODE_UNINIT we don't want to depend
- * on the value of bg_itable_unused even though
- * mke2fs could have initialized the same for us.
- * Instead we calculated the value below
- */
-
- free = 0;
- } else {
- free = EXT4_INODES_PER_GROUP(sb) -
- ext4_itable_unused_count(sb, gdp);
- }
-
- /*
- * Check the relative inode number against the last used
- * relative inode number in this group. if it is greater
- * we need to update the bg_itable_unused count
- *
- */
- if (ino > free)
- ext4_itable_unused_set(sb, gdp,
- (EXT4_INODES_PER_GROUP(sb) - ino));
- }
-
- count = ext4_free_inodes_count(sb, gdp) - 1;
- ext4_free_inodes_set(sb, gdp, count);
- if (S_ISDIR(mode)) {
- count = ext4_used_dirs_count(sb, gdp) + 1;
- ext4_used_dirs_set(sb, gdp, count);
- }
- gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
- spin_unlock(sb_bgl_lock(sbi, group));
BUFFER_TRACE(group_desc_bh, "call ext4_journal_dirty_metadata");
err = ext4_journal_dirty_metadata(handle, group_desc_bh);
- if (err) goto fail;
+ if (err)
+ goto fail;
percpu_counter_dec(&sbi->s_freeinodes_counter);
if (S_ISDIR(mode))
--
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