[PATCH v3 1/3] shmem: Keep track of out-of-memory and out-of-space errors

[Gabriel Krisman Bertazi <krisman@collabora.com>]

Keep a per-sb counter of failed shmem allocations for ENOMEM/ENOSPC to
be reported on sysfs.  The sysfs support is done separately on a later
patch.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 include/linux/shmem_fs.h | 3 +++
 mm/shmem.c               | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index e65b80ed09e7..1a7cd9ea9107 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -44,6 +44,9 @@ struct shmem_sb_info {
 	spinlock_t shrinklist_lock;   /* Protects shrinklist */
 	struct list_head shrinklist;  /* List of shinkable inodes */
 	unsigned long shrinklist_len; /* Length of shrinklist */
+
+	unsigned long acct_errors;
+	unsigned long space_errors;
 };
 
 static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
diff --git a/mm/shmem.c b/mm/shmem.c
index a09b29ec2b45..c350fa0a0fff 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -212,8 +212,10 @@ static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 
-	if (shmem_acct_block(info->flags, pages))
+	if (shmem_acct_block(info->flags, pages)) {
+		sbinfo->acct_errors += 1;
 		return false;
+	}
 
 	if (sbinfo->max_blocks) {
 		if (percpu_counter_compare(&sbinfo->used_blocks,
@@ -225,6 +227,7 @@ static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
 	return true;
 
 unacct:
+	sbinfo->space_errors += 1;
 	shmem_unacct_blocks(info->flags, pages);
 	return false;
 }
-- 
2.35.1