syzbot is reporting hung task at blkdev_fallocate() [1], for it can take
minutes with mapping->invalidate_lock held. Since fallocate() has to accept
64bits size, we can't predict how long it will take. Thus, mitigate this
problem by using killable wait where possible.
----------
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
fork();
fallocate(open("/dev/nullb0", O_RDWR), 0x11, 0, ~0UL >> 1);
return 0;
}
----------
Note that, even after this patch, e.g. "cat /dev/nullb0" can be reported
as hung task at filemap_invalidate_lock_shared() when this reproducer is
running. We will need to also make fault-acceptable reads killable.
__schedule+0x9a0/0xb20
schedule+0xc1/0x120
rwsem_down_read_slowpath+0x3b5/0x670
__down_read_common+0x56/0x1f0
page_cache_ra_unbounded+0x12d/0x400
filemap_read+0x4bb/0x1280
blkdev_read_iter+0x1d5/0x260
vfs_read+0x5f8/0x690
ksys_read+0xee/0x190
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
Link: https://syzkaller.appspot.com/bug?extid=39b75c02b8be0a061bfc [1]
Reported-by: syzbot <syzbot+39b75c02b8be0a061bfc@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
Changes in v2:
Converted all users in block/ directory and fs/open.c file.
I didn't convert remaining users because remaining users should be
carefully converted by each filesystem's developers.
block/blk-zoned.c | 3 ++-
block/fops.c | 3 ++-
block/ioctl.c | 6 ++++--
fs/open.c | 3 ++-
include/linux/fs.h | 5 +++++
5 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 38cd840d8838..07a8841f4724 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -422,7 +422,8 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
op = REQ_OP_ZONE_RESET;
/* Invalidate the page cache, including dirty pages. */
- filemap_invalidate_lock(bdev->bd_inode->i_mapping);
+ if (filemap_invalidate_lock_killable(bdev->bd_inode->i_mapping))
+ return -EINTR;
ret = blkdev_truncate_zone_range(bdev, mode, &zrange);
if (ret)
goto fail;
diff --git a/block/fops.c b/block/fops.c
index ba5e7d5ff9a5..418fb1d789ff 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -656,7 +656,8 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
if ((start | len) & (bdev_logical_block_size(bdev) - 1))
return -EINVAL;
- filemap_invalidate_lock(inode->i_mapping);
+ if (filemap_invalidate_lock_killable(inode->i_mapping))
+ return -EINTR;
/* Invalidate the page cache, including dirty pages. */
error = truncate_bdev_range(bdev, file->f_mode, start, end);
diff --git a/block/ioctl.c b/block/ioctl.c
index 4a86340133e4..13f863f79f68 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -111,7 +111,8 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
if (start + len > bdev_nr_bytes(bdev))
return -EINVAL;
- filemap_invalidate_lock(inode->i_mapping);
+ if (filemap_invalidate_lock_killable(inode->i_mapping))
+ return -EINTR;
err = truncate_bdev_range(bdev, mode, start, start + len - 1);
if (err)
goto fail;
@@ -152,7 +153,8 @@ static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
return -EINVAL;
/* Invalidate the page cache, including dirty pages */
- filemap_invalidate_lock(inode->i_mapping);
+ if (filemap_invalidate_lock_killable(inode->i_mapping))
+ return -EINTR;
err = truncate_bdev_range(bdev, mode, start, end);
if (err)
goto fail;
diff --git a/fs/open.c b/fs/open.c
index 7b50d7a2f51d..adf62e1c186b 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -859,7 +859,8 @@ static int do_dentry_open(struct file *f,
if (filemap_nr_thps(inode->i_mapping)) {
struct address_space *mapping = inode->i_mapping;
- filemap_invalidate_lock(inode->i_mapping);
+ if (filemap_invalidate_lock_killable(inode->i_mapping))
+ return -EINTR;
/*
* unmap_mapping_range just need to be called once
* here, because the private pages is not need to be
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 03f8d95bd4ef..e0134c372b6d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -797,6 +797,11 @@ static inline void filemap_invalidate_lock(struct address_space *mapping)
down_write(&mapping->invalidate_lock);
}
+static inline int filemap_invalidate_lock_killable(struct address_space *mapping)
+{
+ return down_write_killable(&mapping->invalidate_lock);
+}
+
static inline void filemap_invalidate_unlock(struct address_space *mapping)
{
up_write(&mapping->invalidate_lock);
--
2.32.0
