From 1f60fbe7274918adb8db2f616e321890730ab7e3 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sat, 23 Apr 2016 22:50:07 -0400 Subject: [PATCH] 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 Google-Bug-Id: 27880676 Signed-off-by: Theodore Ts'o --- 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 a71936a3f4cb..f940cb20562f 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 561d7308b393..4173bfe21114 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 48e4b8907826..c07422d254b6 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 e69ef3b79787..5f2d4bee5a73 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; } -- 2.39.5