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devfs: Do not perform synchronous requests in devfs_io. 

In some circumstances, we can wind up iterating on requests
by recursing through this function once per "iteration" due to
how vfs_synchronous_io works. This can run out of stack, as
was seen in #9900 and potentially other tickets.

An initial attempt was made to fix the problem in hrev45906,
but it was quickly reverted because it seems to have broken
I/O for all devices that do not support the "IO" hook.

This solution is much simpler: the VFS layer already can handle
vnodes' IO hooks returning B_UNSUPPORTED and then falling back
to synchronous I/O just as if they had no IO hook at all.
This should hopefully cause iteration to occur without recursion.

Tested by booting off a USB drive (the usb_disk driver does not
support the IO hook, so all requests must be translated.)

May fix #9900.
This commit is contained in:
Augustin Cavalier 2022-06-07 14:30:21 -04:00
parent 25742b78fb
commit c146183167
1 changed files with 5 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
src/system/kernel/device_manager/devfs.cpp
View File

@ -149,11 +149,6 @@ struct devfs_cookie {
void* device_cookie;
};
struct synchronous_io_cookie {
BaseDevice* device;
void* cookie;
};
// directory iteration states
enum {
ITERATION_STATE_DOT = 0,
@ -818,22 +813,6 @@ get_device_name(struct devfs_vnode* vnode, char* buffer, size_t size)
}
static status_t
device_read(void* _cookie, off_t offset, void* buffer, size_t* length)
{
synchronous_io_cookie* cookie = (synchronous_io_cookie*)_cookie;
return cookie->device->Read(cookie->cookie, offset, buffer, length);
}
static status_t
device_write(void* _cookie, off_t offset, void* buffer, size_t* length)
{
synchronous_io_cookie* cookie = (synchronous_io_cookie*)_cookie;
return cookie->device->Write(cookie->cookie, offset, buffer, length);
}
static int
dump_node(int argc, char** argv)
{
@ -1828,17 +1807,14 @@ devfs_io(fs_volume* volume, fs_vnode* _vnode, void* _cookie,
devfs_vnode* vnode = (devfs_vnode*)_vnode->private_node;
devfs_cookie* cookie = (devfs_cookie*)_cookie;
bool isWrite = request->IsWrite();
if (!S_ISCHR(vnode->stream.type)
|| (((isWrite && !vnode->stream.u.dev.device->HasWrite())
|| (!isWrite && !vnode->stream.u.dev.device->HasRead()))
&& !vnode->stream.u.dev.device->HasIO())
|| cookie == NULL) {
if (!S_ISCHR(vnode->stream.type) || cookie == NULL) {
request->SetStatusAndNotify(B_NOT_ALLOWED);
return B_NOT_ALLOWED;
}
if (!vnode->stream.u.dev.device->HasIO())
return B_UNSUPPORTED;
if (vnode->stream.u.dev.partition != NULL) {
if (request->Offset() + (off_t)request->Length()
> vnode->stream.u.dev.partition->info.size) {
@ -1848,16 +1824,7 @@ devfs_io(fs_volume* volume, fs_vnode* _vnode, void* _cookie,
translate_partition_access(vnode->stream.u.dev.partition, request);
}
if (vnode->stream.u.dev.device->HasIO())
return vnode->stream.u.dev.device->IO(cookie->device_cookie, request);
synchronous_io_cookie synchronousCookie = {
vnode->stream.u.dev.device,
cookie->device_cookie
};
return vfs_synchronous_io(request,
request->IsWrite() ? &device_write : &device_read, &synchronousCookie);
return vnode->stream.u.dev.device->IO(cookie->device_cookie, request);
}