quota: Prevent memory allocation recursion while holding dq_lock

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>

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index a74aef9..09d1307 100644 (file)
--- 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;
 }