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@xxxxxxxxx>
Google-Bug-Id: 27880676
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
---
fs/compat.c | 4 ++++
fs/ext4/dir.c | 5 +++++
fs/ext4/namei.c | 5 +++++
fs/readdir.c | 4 ++++
4 files changed, 18 insertions(+)
diff --git a/fs/compat.c b/fs/compat.c
index a71936a..f940cb2 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -936,6 +936,8 @@ static int compat_filldir(struct dir_context *ctx, const char *name, int namlen,
}
dirent = buf->previous;
if (dirent) {
+ if (signal_pending(current))
+ return -EINTR;
if (__put_user(offset, &dirent->d_off))
goto efault;
}
@@ -1020,6 +1022,8 @@ static int compat_filldir64(struct dir_context *ctx, const char *name,
dirent = buf->previous;
if (dirent) {
+ if (signal_pending(current))
+ return -EINTR;
if (__put_user_unaligned(offset, &dirent->d_off))
goto efault;
}
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 @@ 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..c07422d 100644
--- 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 (fatal_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);
diff --git a/fs/readdir.c b/fs/readdir.c
index e69ef3b..5f2d4be 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -169,6 +169,8 @@ static int filldir(struct dir_context *ctx, const char *name, int namlen,
}
dirent = buf->previous;
if (dirent) {
+ if (signal_pending(current))
+ return -EINTR;
if (__put_user(offset, &dirent->d_off))
goto efault;
}
@@ -248,6 +250,8 @@ static int filldir64(struct dir_context *ctx, const char *name, int namlen,
return -EINVAL;
dirent = buf->previous;
if (dirent) {
+ if (signal_pending(current))
+ return -EINTR;
if (__put_user(offset, &dirent->d_off))
goto efault;
}
--
2.5.0
--
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