[PATCH v2] f2fs: handle error cases of memory donation

[Daeho Jeong <daeho43@gmail.com>]

From: Daeho Jeong <daehojeong@google.com>

In cases of removing memory donation, we need to handle some error cases
like ENOENT and EACCES (indicating the range already has been donated).

Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
v2: use proper error code
    rename FI_DONATE_FINISHED and use it to fix race conditions
---
 fs/f2fs/f2fs.h     |  1 +
 fs/f2fs/file.c     | 23 ++++++++++++++++-------
 fs/f2fs/shrinker.c | 13 ++++++++++---
 3 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index f1576dc6ec67..01ee8bbb5c84 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -821,6 +821,7 @@ enum {
 	FI_ATOMIC_DIRTIED,	/* indicate atomic file is dirtied */
 	FI_ATOMIC_REPLACE,	/* indicate atomic replace */
 	FI_OPENED_FILE,		/* indicate file has been opened */
+	FI_DONATE_FINISHED,	/* indicate page donation of file has been finished */
 	FI_MAX,			/* max flag, never be used */
 };
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index abbcbb5865a3..61b88431fd43 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2464,19 +2464,20 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
 	return ret;
 }
 
-static void f2fs_keep_noreuse_range(struct inode *inode,
+static int f2fs_keep_noreuse_range(struct inode *inode,
 				loff_t offset, loff_t len)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	u64 max_bytes = F2FS_BLK_TO_BYTES(max_file_blocks(inode));
 	u64 start, end;
+	int ret = 0;
 
 	if (!S_ISREG(inode->i_mode))
-		return;
+		return 0;
 
 	if (offset >= max_bytes || len > max_bytes ||
 	    (offset + len) > max_bytes)
-		return;
+		return 0;
 
 	start = offset >> PAGE_SHIFT;
 	end = DIV_ROUND_UP(offset + len, PAGE_SIZE);
@@ -2484,7 +2485,7 @@ static void f2fs_keep_noreuse_range(struct inode *inode,
 	inode_lock(inode);
 	if (f2fs_is_atomic_file(inode)) {
 		inode_unlock(inode);
-		return;
+		return 0;
 	}
 
 	spin_lock(&sbi->inode_lock[DONATE_INODE]);
@@ -2493,7 +2494,12 @@ static void f2fs_keep_noreuse_range(struct inode *inode,
 		if (!list_empty(&F2FS_I(inode)->gdonate_list)) {
 			list_del_init(&F2FS_I(inode)->gdonate_list);
 			sbi->donate_files--;
-		}
+			if (is_inode_flag_set(inode, FI_DONATE_FINISHED))
+				ret = -EALREADY;
+			else
+				set_inode_flag(inode, FI_DONATE_FINISHED);
+		} else
+			ret = -ENOENT;
 	} else {
 		if (list_empty(&F2FS_I(inode)->gdonate_list)) {
 			list_add_tail(&F2FS_I(inode)->gdonate_list,
@@ -2505,9 +2511,12 @@ static void f2fs_keep_noreuse_range(struct inode *inode,
 		}
 		F2FS_I(inode)->donate_start = start;
 		F2FS_I(inode)->donate_end = end - 1;
+		clear_inode_flag(inode, FI_DONATE_FINISHED);
 	}
 	spin_unlock(&sbi->inode_lock[DONATE_INODE]);
 	inode_unlock(inode);
+
+	return ret;
 }
 
 static int f2fs_ioc_fitrim(struct file *filp, unsigned long arg)
@@ -5236,8 +5245,8 @@ static int f2fs_file_fadvise(struct file *filp, loff_t offset, loff_t len,
 	     f2fs_compressed_file(inode)))
 		f2fs_invalidate_compress_pages(F2FS_I_SB(inode), inode->i_ino);
 	else if (advice == POSIX_FADV_NOREUSE)
-		f2fs_keep_noreuse_range(inode, offset, len);
-	return 0;
+		err = f2fs_keep_noreuse_range(inode, offset, len);
+	return err;
 }
 
 #ifdef CONFIG_COMPAT
diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
index 9c8d3aee89af..b88babcf6ab4 100644
--- a/fs/f2fs/shrinker.c
+++ b/fs/f2fs/shrinker.c
@@ -184,10 +184,17 @@ static unsigned int do_reclaim_caches(struct f2fs_sb_info *sbi,
 		if (!inode)
 			continue;
 
-		len = fi->donate_end - fi->donate_start + 1;
-		npages = npages < len ? 0 : npages - len;
-		invalidate_inode_pages2_range(inode->i_mapping,
+		inode_lock(inode);
+		if (!is_inode_flag_set(inode, FI_DONATE_FINISHED)) {
+			len = fi->donate_end - fi->donate_start + 1;
+			npages = npages < len ? 0 : npages - len;
+
+			invalidate_inode_pages2_range(inode->i_mapping,
 					fi->donate_start, fi->donate_end);
+			set_inode_flag(inode, FI_DONATE_FINISHED);
+		}
+		inode_unlock(inode);
+
 		iput(inode);
 		cond_resched();
 	}
-- 
2.49.0.805.g082f7c87e0-goog