f2fs: fix to limit gc_pin_file_threshold

type of f2fs_inode.i_gc_failures, f2fs_inode_info.i_gc_failures, and
f2fs_sb_info.gc_pin_file_threshold is __le16, unsigned int, and u64,
so it will cause truncation during comparison and persistence.

Unifying variable of these three variables to unsigned short, and
add an upper boundary limitation for gc_pin_file_threshold.
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -331,7 +331,7 @@ Date:		January 2018
 Contact:	Jaegeuk Kim <jaegeuk@kernel.org>
 Description:	This indicates how many GC can be failed for the pinned
 		file. If it exceeds this, F2FS doesn't guarantee its pinning
-		state. 2048 trials is set by default.
+		state. 2048 trials is set by default, and 65535 as maximum.
 
 What:		/sys/fs/f2fs/<disk>/extension_list
 Date:		February 2018

fs/f2fs/f2fs.h

@@ -813,7 +813,7 @@ struct f2fs_inode_info {
 	unsigned char i_dir_level;	/* use for dentry level for large dir */
 	union {
 		unsigned int i_current_depth;	/* only for directory depth */
-		unsigned int i_gc_failures;	/* for gc failure statistic */
+		unsigned short i_gc_failures;	/* for gc failure statistic */
 	};
 	unsigned int i_pino;		/* parent inode number */
 	umode_t i_acl_mode;		/* keep file acl mode temporarily */
@@ -1673,7 +1673,7 @@ struct f2fs_sb_info {
 	unsigned long long skipped_gc_rwsem;		/* FG_GC only */
 
 	/* threshold for gc trials on pinned files */
-	u64 gc_pin_file_threshold;
+	unsigned short gc_pin_file_threshold;
 	struct f2fs_rwsem pin_sem;
 
 	/* maximum # of trials to find a victim segment for SSR and GC */

fs/f2fs/file.c

@@ -3215,16 +3215,17 @@ int f2fs_pin_file_control(struct inode *inode, bool inc)
 	struct f2fs_inode_info *fi = F2FS_I(inode);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 
-	/* Use i_gc_failures for normal file as a risk signal. */
-	if (inc)
-		f2fs_i_gc_failures_write(inode, fi->i_gc_failures + 1);
-
-	if (fi->i_gc_failures > sbi->gc_pin_file_threshold) {
+	if (fi->i_gc_failures >= sbi->gc_pin_file_threshold) {
 		f2fs_warn(sbi, "%s: Enable GC = ino %lx after %x GC trials",
 			  __func__, inode->i_ino, fi->i_gc_failures);
 		clear_inode_flag(inode, FI_PIN_FILE);
 		return -EAGAIN;
 	}
+
+	/* Use i_gc_failures for normal file as a risk signal. */
+	if (inc)
+		f2fs_i_gc_failures_write(inode, fi->i_gc_failures + 1);
+
 	return 0;
 }
 

fs/f2fs/gc.h

@@ -26,6 +26,7 @@
 #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
 
 #define DEF_GC_FAILED_PINNED_FILES	2048
+#define MAX_GC_FAILED_PINNED_FILES	USHRT_MAX
 
 /* Search max. number of dirty segments to select a victim segment */
 #define DEF_MAX_VICTIM_SEARCH 4096 /* covers 8GB */

fs/f2fs/sysfs.c

@@ -675,6 +675,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 		return count;
 	}
 
+	if (!strcmp(a->attr.name, "gc_pin_file_threshold")) {
+		if (t > MAX_GC_FAILED_PINNED_FILES)
+			return -EINVAL;
+		sbi->gc_pin_file_threshold = t;
+		return count;
+	}
+
 	if (!strcmp(a->attr.name, "gc_reclaimed_segments")) {
 		if (t != 0)
 			return -EINVAL;