[PATCH 5.15 018/106] quota: Prevent memory allocation recursion while holding dq_lock

Greg Kroah-Hartman
2022-06-20T13:35:21Z

From: Matthew Wilcox (Oracle) <willy@infradead.org>

[ Upstream commit 537e11cdc7a6b3ce94fa25ed41306193df9677b7 ]

As described in commit 02117b8ae9c0 ("f2fs: Set GF_NOFS in
read_cache_page_gfp while doing f2fs_quota_read"), we must not enter
filesystem reclaim while holding the dq_lock. Prevent this more generally
by using memalloc_nofs_save() while holding the lock.

Link: https://lore.kernel.org/r/20220605143815.2330891-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/quota/dquot.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index a74aef99bd3d..09d1307959d0 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -79,6 +79,7 @@
#include <linux/capability.h>
#include <linux/quotaops.h>
#include <linux/blkdev.h>
+#include <linux/sched/mm.h>
#include "../internal.h" /* ugh */

#include <linux/uaccess.h>
@@ -425,9 +426,11 @@ EXPORT_SYMBOL(mark_info_dirty);
int dquot_acquire(struct dquot *dquot)
{
int ret = 0, ret2 = 0;
+ unsigned int memalloc;
struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);

mutex_lock(&dquot->dq_lock);
+ memalloc = memalloc_nofs_save();
if (!test_bit(DQ_READ_B, &dquot->dq_flags)) {
ret = dqopt->ops[dquot->dq_id.type]->read_dqblk(dquot);
if (ret < 0)
@@ -458,6 +461,7 @@ int dquot_acquire(struct dquot *dquot)
smp_mb__before_atomic();
set_bit(DQ_ACTIVE_B, &dquot->dq_flags);
out_iolock:
+ memalloc_nofs_restore(memalloc);
mutex_unlock(&dquot->dq_lock);
return ret;
}
@@ -469,9 +473,11 @@ EXPORT_SYMBOL(dquot_acquire);
int dquot_commit(struct dquot *dquot)
{
int ret = 0;
+ unsigned int memalloc;
struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);

mutex_lock(&dquot->dq_lock);
+ memalloc = memalloc_nofs_save();
if (!clear_dquot_dirty(dquot))
goto out_lock;
/* Inactive dquot can be only if there was error during read/init
@@ -481,6 +487,7 @@ int dquot_commit(struct dquot *dquot)
else
ret = -EIO;
out_lock:
+ memalloc_nofs_restore(memalloc);
mutex_unlock(&dquot->dq_lock);
return ret;
}
@@ -492,9 +499,11 @@ EXPORT_SYMBOL(dquot_commit);
int dquot_release(struct dquot *dquot)
{
int ret = 0, ret2 = 0;
+ unsigned int memalloc;
struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);

mutex_lock(&dquot->dq_lock);
+ memalloc = memalloc_nofs_save();
/* Check whether we are not racing with some other dqget() */
if (dquot_is_busy(dquot))
goto out_dqlock;
@@ -510,6 +519,7 @@ int dquot_release(struct dquot *dquot)
}
clear_bit(DQ_ACTIVE_B, &dquot->dq_flags);
out_dqlock:
+ memalloc_nofs_restore(memalloc);
mutex_unlock(&dquot->dq_lock);
return ret;
}
--
2.35.1