4 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 1b7f9acbcbbe..104322bf378c 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -375,6 +375,16 @@ dioread_nolock		locking. If the dioread_nolock option is specified
                         Because of the restrictions this options comprises
                         it is off by default (e.g. dioread_lock).
 
+max_dir_size_kb=n       This limits the size of directories so that any
+                        attempt to expand them beyond the specified
+                        limit in kilobytes will cause an ENOSPC error.
+                        This is useful in memory constrained
+                        environments, where a very large directory can
+                        cause severe performance problems or even
+                        provoke the Out Of Memory killer.  (For example,
+                        if there is only 512mb memory available, a 176mb
+                        directory may seriously cramp the system's style.)
+
 i_version               Enable 64-bit inode version support. This option is
                         off by default.
 
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index c3411d4ce2da..7c0841ecde6c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1243,6 +1243,7 @@ struct ext4_sb_info {
         unsigned int s_mb_order2_reqs;
         unsigned int s_mb_group_prealloc;
         unsigned int s_max_writeback_mb_bump;
+        unsigned int s_max_dir_size_kb;
         /* where last allocation was done - for stream allocation */
         unsigned long s_mb_last_group;
         unsigned long s_mb_last_start;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 2a42cc04466f..7450ff01c3c4 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -55,6 +55,13 @@ static struct buffer_head *ext4_append(handle_t *handle,
 {
         struct buffer_head *bh;
 
+        if (unlikely(EXT4_SB(inode->i_sb)->s_max_dir_size_kb &&
+                     ((inode->i_size >> 10) >=
+                      EXT4_SB(inode->i_sb)->s_max_dir_size_kb))) {
+                *err = -ENOSPC;
+                return NULL;
+        }
+
         *block = inode->i_size >> inode->i_sb->s_blocksize_bits;
 
         bh = ext4_bread(handle, inode, *block, 1, err);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 598498904035..5a97e590692d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1230,6 +1230,7 @@ enum {
         Opt_inode_readahead_blks, Opt_journal_ioprio,
         Opt_dioread_nolock, Opt_dioread_lock,
         Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
+        Opt_max_dir_size_kb,
 };
 
 static const match_table_t tokens = {
@@ -1303,6 +1304,7 @@ static const match_table_t tokens = {
         {Opt_init_itable, "init_itable=%u"},
         {Opt_init_itable, "init_itable"},
         {Opt_noinit_itable, "noinit_itable"},
+        {Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
         {Opt_removed, "check=none"},    /* mount option from ext2/3 */
         {Opt_removed, "nocheck"},       /* mount option from ext2/3 */
         {Opt_removed, "reservation"},   /* mount option from ext2/3 */
@@ -1483,6 +1485,7 @@ static const struct mount_opts {
         {Opt_jqfmt_vfsold, QFMT_VFS_OLD, MOPT_QFMT},
         {Opt_jqfmt_vfsv0, QFMT_VFS_V0, MOPT_QFMT},
         {Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
+        {Opt_max_dir_size_kb, 0, MOPT_GTE0},
         {Opt_err, 0, 0}
 };
 
@@ -1598,6 +1601,8 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
                         if (!args->from)
                                 arg = EXT4_DEF_LI_WAIT_MULT;
                         sbi->s_li_wait_mult = arg;
+                } else if (token == Opt_max_dir_size_kb) {
+                        sbi->s_max_dir_size_kb = arg;
                 } else if (token == Opt_stripe) {
                         sbi->s_stripe = arg;
                 } else if (m->flags & MOPT_DATAJ) {
@@ -1829,6 +1834,8 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
         if (nodefs || (test_opt(sb, INIT_INODE_TABLE) &&
                        (sbi->s_li_wait_mult != EXT4_DEF_LI_WAIT_MULT)))
                 SEQ_OPTS_PRINT("init_itable=%u", sbi->s_li_wait_mult);
+        if (nodefs || sbi->s_max_dir_size_kb)
+                SEQ_OPTS_PRINT("max_dir_size_kb=%u", sbi->s_max_dir_size_kb);
 
         ext4_show_quota_options(seq, sb);
         return 0;