From 5c2d728507299f84631ab8020d6f0f98f2cb8fc2 Mon Sep 17 00:00:00 2001

From: Hyeongseok Kim <hyeongseok@gmail.com>

Date: Tue, 2 Mar 2021 14:05:20 +0900

Subject: [Backport 5c2d72850729] exfat: introduce bitmap_lock for cluster

 bitmap access

s_lock which is for protecting concurrent access of file operations is

too huge for cluster bitmap protection, so introduce a new bitmap_lock

to narrow the lock range if only need to access cluster bitmap.

Signed-off-by: Hyeongseok Kim <hyeongseok@gmail.com>

Acked-by: Sungjong Seo <sj1557.seo@samsung.com>

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

---

 src/exfat_fs.h |  1 +

 src/fatent.c   | 37 +++++++++++++++++++++++++++++--------

 src/super.c    |  1 +

 3 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/exfat_fs.h b/src/exfat_fs.h

index fa21421a14d9e047add5b9b03c0970b4fd4d7522..e05e0a3152c0e5c415bd042e40d680194f02b49e 100644

--- a/src/exfat_fs.h

+++ b/src/exfat_fs.h

@@ -238,6 +238,7 @@ struct exfat_sb_info {

 	unsigned int used_clusters; /* number of used clusters */

 	struct mutex s_lock; /* superblock lock */

+	struct mutex bitmap_lock; /* bitmap lock */

 	struct exfat_mount_options options;

 	struct nls_table *nls_io; /* Charset used for input and display */

 	struct ratelimit_state ratelimit;

diff --git a/src/fatent.c b/src/fatent.c

index 7b2e8af17193bfffe00b4e0b8b88cccb34b1970a..fd6c7fd127620fc405cff2b5ae2d6fae5be25422 100644

--- a/src/fatent.c

+++ b/src/fatent.c

@@ -151,13 +151,14 @@ int exfat_chain_cont_cluster(struct super_block *sb, unsigned int chain,

 	return 0;

 }

-int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)

+/* This function must be called with bitmap_lock held */

+static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)

 {

-	unsigned int num_clusters = 0;

-	unsigned int clu;

 	struct super_block *sb = inode->i_sb;

 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	int cur_cmap_i, next_cmap_i;

+	unsigned int num_clusters = 0;

+	unsigned int clu;

 	/* invalid cluster number */

 	if (p_chain->dir == EXFAT_FREE_CLUSTER ||

@@ -230,6 +231,17 @@ int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)

 	return 0;

 }

+int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)

+{

+	int ret = 0;

+

+	mutex_lock(&EXFAT_SB(inode->i_sb)->bitmap_lock);

+	ret = __exfat_free_cluster(inode, p_chain);

+	mutex_unlock(&EXFAT_SB(inode->i_sb)->bitmap_lock);

+

+	return ret;

+}

+

 int exfat_find_last_cluster(struct super_block *sb, struct exfat_chain *p_chain,

 		unsigned int *ret_clu)

 {

@@ -328,6 +340,8 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,

 	if (num_alloc > total_cnt - sbi->used_clusters)

 		return -ENOSPC;

+	mutex_lock(&sbi->bitmap_lock);

+

 	hint_clu = p_chain->dir;

 	/* find new cluster */

 	if (hint_clu == EXFAT_EOF_CLUSTER) {

@@ -338,8 +352,10 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,

 		}

 		hint_clu = exfat_find_free_bitmap(sb, sbi->clu_srch_ptr);

-		if (hint_clu == EXFAT_EOF_CLUSTER)

-			return -ENOSPC;

+		if (hint_clu == EXFAT_EOF_CLUSTER) {

+			ret = -ENOSPC;

+			goto unlock;

+		}

 	}

 	/* check cluster validation */

@@ -349,8 +365,10 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,

 		hint_clu = EXFAT_FIRST_CLUSTER;

 		if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {

 			if (exfat_chain_cont_cluster(sb, p_chain->dir,

-					num_clusters))

-				return -EIO;

+					num_clusters)) {

+				ret = -EIO;

+				goto unlock;

+			}

 			p_chain->flags = ALLOC_FAT_CHAIN;

 		}

 	}

@@ -400,6 +418,7 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,

 			sbi->used_clusters += num_clusters;

 			p_chain->size += num_clusters;

+			mutex_unlock(&sbi->bitmap_lock);

 			return 0;

 		}

@@ -419,7 +438,9 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,

 	}

 free_cluster:

 	if (num_clusters)

-		exfat_free_cluster(inode, p_chain);

+		__exfat_free_cluster(inode, p_chain);

+unlock:

+	mutex_unlock(&sbi->bitmap_lock);

 	return ret;

 }

diff --git a/src/super.c b/src/super.c

index c6d8d2e534865236d16386575627e0a442a8db52..d38d17a77e76c45a006abeae532a6ae3170529d7 100644

--- a/src/super.c

+++ b/src/super.c

@@ -752,6 +752,7 @@ static int exfat_init_fs_context(struct fs_context *fc)

 		return -ENOMEM;

 	mutex_init(&sbi->s_lock);

+	mutex_init(&sbi->bitmap_lock);

 	ratelimit_state_init(&sbi->ratelimit, DEFAULT_RATELIMIT_INTERVAL,

 			DEFAULT_RATELIMIT_BURST);

-- 

2.31.1