Commit 537e11cd authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Jan Kara
Browse files

quota: Prevent memory allocation recursion while holding dq_lock 

As described in commit 02117b8a ("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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 10e14073

fs/quota/dquot.c

+10 −0
Original line number Diff line number Diff line
@@ -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;

}