ext4: allow readdir()'s of large empty directories to be interrupted

If a directory has a large number of empty blocks, iterating over all
of them can take a long time, leading to scheduler warnings and users
getting irritated when they can't kill a process in the middle of one
of these long-running readdir operations.  Fix this by adding checks to
ext4_readdir() and ext4_htree_fill_tree().

Reported-by: Benjamin LaHaise <bcrl@kvack.org>
Google-Bug-Id: 27880676
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 33f5e2a..ebfcb89 100644 (file)
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -150,6 +150,11 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
        while (ctx->pos < inode->i_size) {
                struct ext4_map_blocks map;
 
+               if (fatal_signal_pending(current)) {
+                       err = -ERESTARTSYS;
+                       goto errout;
+               }
+               cond_resched();
                map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
                map.m_len = 1;
                err = ext4_map_blocks(NULL, inode, &map, 0);

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 48e4b89..db98f89 100644 (file)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1107,6 +1107,11 @@ int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash,
        }
 
        while (1) {
+               if (signal_pending(current)) {
+                       err = -ERESTARTSYS;
+                       goto errout;
+               }
+               cond_resched();
                block = dx_get_block(frame->at);
                ret = htree_dirblock_to_tree(dir_file, dir, block, &hinfo,
                                             start_hash, start_minor_hash);