5.10-stable review patch. If anyone has any objections, please let me know.
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From: Li Jinlin lijinlin3@huawei.com
commit 17d9c15c9b9e7fb285f7ac5367dfb5f00ff575e3 upstream.
I got an infinite loop and a WARNING report when executing a tail command in virtiofs.
WARNING: CPU: 10 PID: 964 at fs/iomap/iter.c:34 iomap_iter+0x3a2/0x3d0 Modules linked in: CPU: 10 PID: 964 Comm: tail Not tainted 5.19.0-rc7 Call Trace: <TASK> dax_iomap_rw+0xea/0x620 ? __this_cpu_preempt_check+0x13/0x20 fuse_dax_read_iter+0x47/0x80 fuse_file_read_iter+0xae/0xd0 new_sync_read+0xfe/0x180 ? 0xffffffff81000000 vfs_read+0x14d/0x1a0 ksys_read+0x6d/0xf0 __x64_sys_read+0x1a/0x20 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd
The tail command will call read() with a count of 0. In this case, iomap_iter() will report this WARNING, and always return 1 which casuing the infinite loop in dax_iomap_rw().
Fixing by checking count whether is 0 in dax_iomap_rw().
Fixes: ca289e0b95af ("fsdax: switch dax_iomap_rw to use iomap_iter") Signed-off-by: Li Jinlin lijinlin3@huawei.com Reviewed-by: Darrick J. Wong djwong@kernel.org Link: https://lore.kernel.org/r/20220725032050.3873372-1-lijinlin3@huawei.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/dax.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/fs/dax.c +++ b/fs/dax.c @@ -1219,6 +1219,9 @@ dax_iomap_rw(struct kiocb *iocb, struct loff_t done = 0; int ret;
+ if (!iomi.len) + return 0; + if (iov_iter_rw(iter) == WRITE) { lockdep_assert_held_write(&iomi.inode->i_rwsem); iomi.flags |= IOMAP_WRITE;