f2fs: avoid potential deadlock in f2fs_sbi_store

[android-x86/kernel.git] / fs / f2fs / sysfs.c

diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 2e7e611..bca1236 100644 (file)
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -9,6 +9,7 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
+#include <linux/compiler.h>
 #include <linux/proc_fs.h>
 #include <linux/f2fs_fs.h>
 #include <linux/seq_file.h>
@@ -286,8 +287,10 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
        bool gc_entry = (!strcmp(a->attr.name, "gc_urgent") ||
                                        a->struct_type == GC_THREAD);
 
-       if (gc_entry)
-               down_read(&sbi->sb->s_umount);
+       if (gc_entry) {
+               if (!down_read_trylock(&sbi->sb->s_umount))
+                       return -EAGAIN;
+       }
        ret = __sbi_store(a, sbi, buf, count);
        if (gc_entry)
                up_read(&sbi->sb->s_umount);
@@ -516,7 +519,8 @@ static struct kobject f2fs_feat = {
        .kset   = &f2fs_kset,
 };
 
-static int segment_info_seq_show(struct seq_file *seq, void *offset)
+static int __maybe_unused segment_info_seq_show(struct seq_file *seq,
+                                               void *offset)
 {
        struct super_block *sb = seq->private;
        struct f2fs_sb_info *sbi = F2FS_SB(sb);
@@ -543,7 +547,8 @@ static int segment_info_seq_show(struct seq_file *seq, void *offset)
        return 0;
 }
 
-static int segment_bits_seq_show(struct seq_file *seq, void *offset)
+static int __maybe_unused segment_bits_seq_show(struct seq_file *seq,
+                                               void *offset)
 {
        struct super_block *sb = seq->private;
        struct f2fs_sb_info *sbi = F2FS_SB(sb);
@@ -567,7 +572,8 @@ static int segment_bits_seq_show(struct seq_file *seq, void *offset)
        return 0;
 }
 
-static int iostat_info_seq_show(struct seq_file *seq, void *offset)
+static int __maybe_unused iostat_info_seq_show(struct seq_file *seq,
+                                              void *offset)
 {
        struct super_block *sb = seq->private;
        struct f2fs_sb_info *sbi = F2FS_SB(sb);