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().
This was reverted earlier due to a typo in the original commit where I
experimented with using signal_pending() instead of
fatal_signal_pending(). The test was in the wrong place if we were
going to return signal_pending() since we would end up returning
duplicant entries. See 9f2394c9be47 for a more detailed explanation.
Added fix as suggested by Linus to check for signal_pending() in
in the filldir() functions.
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 561d730..4173bfe 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -150,6 +150,11 @@
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);