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ocfs2: Fix possible deadlock when extending quota file
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In OCFS2, allocator locks rank above transaction start. Thus we
cannot extend quota file from inside a transaction less we could
deadlock.

We solve the problem by starting transaction not already in
ocfs2_acquire_dquot() but only in ocfs2_local_read_dquot() and
ocfs2_global_read_dquot() and we allocate blocks to quota files before starting
the transaction.  In case we crash, quota files will just have a few blocks
more but that's no problem since we just use them next time we extend the
quota file.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
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Jan Kara authored and Joel Becker committed Aug 10, 2009
1 parent 8a57a9d commit b409d7a
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Showing 2 changed files with 57 additions and 63 deletions.
5 changes: 0 additions & 5 deletions fs/ocfs2/journal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -363,11 +363,6 @@ static inline int ocfs2_quota_trans_credits(struct super_block *sb)
return credits;
}

/* Number of credits needed for removing quota structure from file */
int ocfs2_calc_qdel_credits(struct super_block *sb, int type);
/* Number of credits needed for initialization of new quota structure */
int ocfs2_calc_qinit_credits(struct super_block *sb, int type);

/* group extend. inode update and last group update. */
#define OCFS2_GROUP_EXTEND_CREDITS (OCFS2_INODE_UPDATE_CREDITS + 1)

Expand Down
115 changes: 57 additions & 58 deletions fs/ocfs2/quota_global.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -215,11 +215,7 @@ ssize_t ocfs2_quota_write(struct super_block *sb, int type,
loff_t rounded_end =
ocfs2_align_bytes_to_blocks(sb, off + len);

down_write(&OCFS2_I(gqinode)->ip_alloc_sem);
err = ocfs2_extend_no_holes(gqinode, rounded_end, off);
up_write(&OCFS2_I(gqinode)->ip_alloc_sem);
if (err < 0)
goto out;
/* Space is already allocated in ocfs2_global_read_dquot() */
err = ocfs2_simple_size_update(gqinode,
oinfo->dqi_gqi_bh,
rounded_end);
Expand Down Expand Up @@ -405,13 +401,36 @@ int ocfs2_global_write_info(struct super_block *sb, int type)
return err;
}

static int ocfs2_global_qinit_alloc(struct super_block *sb, int type)
{
struct ocfs2_mem_dqinfo *oinfo = sb_dqinfo(sb, type)->dqi_priv;

/*
* We may need to allocate tree blocks and a leaf block but not the
* root block
*/
return oinfo->dqi_gi.dqi_qtree_depth;
}

static int ocfs2_calc_global_qinit_credits(struct super_block *sb, int type)
{
/* We modify all the allocated blocks, tree root, and info block */
return (ocfs2_global_qinit_alloc(sb, type) + 2) *
OCFS2_QUOTA_BLOCK_UPDATE_CREDITS;
}

/* Read in information from global quota file and acquire a reference to it.
* dquot_acquire() has already started the transaction and locked quota file */
int ocfs2_global_read_dquot(struct dquot *dquot)
{
int err, err2, ex = 0;
struct ocfs2_mem_dqinfo *info =
sb_dqinfo(dquot->dq_sb, dquot->dq_type)->dqi_priv;
struct super_block *sb = dquot->dq_sb;
int type = dquot->dq_type;
struct ocfs2_mem_dqinfo *info = sb_dqinfo(sb, type)->dqi_priv;
struct ocfs2_super *osb = OCFS2_SB(sb);
struct inode *gqinode = info->dqi_gqinode;
int need_alloc = ocfs2_global_qinit_alloc(sb, type);
handle_t *handle = NULL;

err = ocfs2_qinfo_lock(info, 0);
if (err < 0)
Expand All @@ -422,14 +441,33 @@ int ocfs2_global_read_dquot(struct dquot *dquot)
OCFS2_DQUOT(dquot)->dq_use_count++;
OCFS2_DQUOT(dquot)->dq_origspace = dquot->dq_dqb.dqb_curspace;
OCFS2_DQUOT(dquot)->dq_originodes = dquot->dq_dqb.dqb_curinodes;
ocfs2_qinfo_unlock(info, 0);

if (!dquot->dq_off) { /* No real quota entry? */
/* Upgrade to exclusive lock for allocation */
ocfs2_qinfo_unlock(info, 0);
err = ocfs2_qinfo_lock(info, 1);
if (err < 0)
goto out_qlock;
ex = 1;
/*
* Add blocks to quota file before we start a transaction since
* locking allocators ranks above a transaction start
*/
WARN_ON(journal_current_handle());
down_write(&OCFS2_I(gqinode)->ip_alloc_sem);
err = ocfs2_extend_no_holes(gqinode,
gqinode->i_size + (need_alloc << sb->s_blocksize_bits),
gqinode->i_size);
up_write(&OCFS2_I(gqinode)->ip_alloc_sem);
if (err < 0)
goto out;
}

handle = ocfs2_start_trans(osb,
ocfs2_calc_global_qinit_credits(sb, type));
if (IS_ERR(handle)) {
err = PTR_ERR(handle);
goto out;
}
err = ocfs2_qinfo_lock(info, ex);
if (err < 0)
goto out_trans;
err = qtree_write_dquot(&info->dqi_gi, dquot);
if (ex && info_dirty(sb_dqinfo(dquot->dq_sb, dquot->dq_type))) {
err2 = __ocfs2_global_write_info(dquot->dq_sb, dquot->dq_type);
Expand All @@ -441,6 +479,9 @@ int ocfs2_global_read_dquot(struct dquot *dquot)
ocfs2_qinfo_unlock(info, 1);
else
ocfs2_qinfo_unlock(info, 0);
out_trans:
if (handle)
ocfs2_commit_trans(osb, handle);
out:
if (err < 0)
mlog_errno(err);
Expand Down Expand Up @@ -638,24 +679,17 @@ static int ocfs2_write_dquot(struct dquot *dquot)
return status;
}

int ocfs2_calc_qdel_credits(struct super_block *sb, int type)
static int ocfs2_calc_qdel_credits(struct super_block *sb, int type)
{
struct ocfs2_mem_dqinfo *oinfo;
int features[MAXQUOTAS] = { OCFS2_FEATURE_RO_COMPAT_USRQUOTA,
OCFS2_FEATURE_RO_COMPAT_GRPQUOTA };

if (!OCFS2_HAS_RO_COMPAT_FEATURE(sb, features[type]))
return 0;

oinfo = sb_dqinfo(sb, type)->dqi_priv;
struct ocfs2_mem_dqinfo *oinfo = sb_dqinfo(sb, type)->dqi_priv;
/*
* We modify tree, leaf block, global info, local chunk header,
* global and local inode; OCFS2_QINFO_WRITE_CREDITS already
* accounts for inode update
*/
return oinfo->dqi_gi.dqi_qtree_depth +
return (oinfo->dqi_gi.dqi_qtree_depth + 2) *
OCFS2_QUOTA_BLOCK_UPDATE_CREDITS +
OCFS2_QINFO_WRITE_CREDITS +
2 * OCFS2_QUOTA_BLOCK_UPDATE_CREDITS +
OCFS2_INODE_UPDATE_CREDITS;
}

Expand Down Expand Up @@ -688,36 +722,10 @@ static int ocfs2_release_dquot(struct dquot *dquot)
return status;
}

int ocfs2_calc_qinit_credits(struct super_block *sb, int type)
{
struct ocfs2_mem_dqinfo *oinfo;
int features[MAXQUOTAS] = { OCFS2_FEATURE_RO_COMPAT_USRQUOTA,
OCFS2_FEATURE_RO_COMPAT_GRPQUOTA };
struct ocfs2_dinode *lfe, *gfe;

if (!OCFS2_HAS_RO_COMPAT_FEATURE(sb, features[type]))
return 0;

oinfo = sb_dqinfo(sb, type)->dqi_priv;
gfe = (struct ocfs2_dinode *)oinfo->dqi_gqi_bh->b_data;
lfe = (struct ocfs2_dinode *)oinfo->dqi_lqi_bh->b_data;
/* We can extend local file + global file. In local file we
* can modify info, chunk header block and dquot block. In
* global file we can modify info, tree and leaf block */
return ocfs2_calc_extend_credits(sb, &lfe->id2.i_list, 0) +
ocfs2_calc_extend_credits(sb, &gfe->id2.i_list, 0) +
OCFS2_LOCAL_QINFO_WRITE_CREDITS +
2 * OCFS2_QUOTA_BLOCK_UPDATE_CREDITS +
oinfo->dqi_gi.dqi_qtree_depth +
2 * OCFS2_QUOTA_BLOCK_UPDATE_CREDITS;
}

static int ocfs2_acquire_dquot(struct dquot *dquot)
{
handle_t *handle;
struct ocfs2_mem_dqinfo *oinfo =
sb_dqinfo(dquot->dq_sb, dquot->dq_type)->dqi_priv;
struct ocfs2_super *osb = OCFS2_SB(dquot->dq_sb);
int status = 0;

mlog_entry("id=%u, type=%d", dquot->dq_id, dquot->dq_type);
Expand All @@ -726,16 +734,7 @@ static int ocfs2_acquire_dquot(struct dquot *dquot)
status = ocfs2_lock_global_qf(oinfo, 1);
if (status < 0)
goto out;
handle = ocfs2_start_trans(osb,
ocfs2_calc_qinit_credits(dquot->dq_sb, dquot->dq_type));
if (IS_ERR(handle)) {
status = PTR_ERR(handle);
mlog_errno(status);
goto out_ilock;
}
status = dquot_acquire(dquot);
ocfs2_commit_trans(osb, handle);
out_ilock:
ocfs2_unlock_global_qf(oinfo, 1);
out:
mlog_exit(status);
Expand Down

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