[LibOS] Clean up select and poll implementations

Signed-off-by: Borys Popławski <[email protected]>

libos/include/libos_fs.h

@@ -21,10 +21,6 @@
 
 struct libos_handle;
 
-#define FS_POLL_RD 0x01
-#define FS_POLL_WR 0x02
-#define FS_POLL_ER 0x04
-
 /* Describes mount parameters. Passed to `mount_fs`, and to the `mount` callback. */
 struct libos_mount_params {
     /* Filesystem type (corresponds to `name` field of `libos_fs` */
@@ -182,8 +178,8 @@ struct libos_fs_ops {
     int (*checkout)(struct libos_handle* hdl);
     int (*checkin)(struct libos_handle* hdl);
 
-    /* poll a single handle */
-    int (*poll)(struct libos_handle* hdl, int poll_type);
+    /* Poll a single handle. Must not block. */
+    int (*poll)(struct libos_handle* hdl, int in_events, int* out_events);
 
     /* checkpoint/migrate the file system */
     ssize_t (*checkpoint)(void** checkpoint, void* mount_data);
@@ -950,7 +946,7 @@ int generic_readdir(struct libos_dentry* dent, readdir_callback_t callback, void
 int generic_inode_stat(struct libos_dentry* dent, struct stat* buf);
 int generic_inode_hstat(struct libos_handle* hdl, struct stat* buf);
 file_off_t generic_inode_seek(struct libos_handle* hdl, file_off_t offset, int origin);
-int generic_inode_poll(struct libos_handle* hdl, int poll_type);
+int generic_inode_poll(struct libos_handle* hdl, int events, int* out_events);
 
 int generic_emulated_mmap(struct libos_handle* hdl, void* addr, size_t size, int prot, int flags,
                           uint64_t offset);

libos/include/libos_fs_mem.h

@@ -30,4 +30,4 @@ ssize_t mem_file_read(struct libos_mem_file* mem, file_off_t pos_start, void* bu
 ssize_t mem_file_write(struct libos_mem_file* mem, file_off_t pos_start, const void* buf,
                        size_t size);
 int mem_file_truncate(struct libos_mem_file* mem, file_off_t size);
-int mem_file_poll(struct libos_mem_file* mem, file_off_t pos, int poll_type);
+int mem_file_poll(struct libos_mem_file* mem, file_off_t pos, int events, int* out_events);

libos/include/libos_table.h

@@ -182,7 +182,7 @@ long libos_syscall_fchmodat(int dfd, const char* filename, mode_t mode);
 long libos_syscall_fchownat(int dfd, const char* filename, uid_t user, gid_t group, int flags);
 long libos_syscall_faccessat(int dfd, const char* filename, mode_t mode);
 long libos_syscall_pselect6(int nfds, fd_set* readfds, fd_set* writefds, fd_set* exceptfds,
-                            const struct __kernel_timespec* tsp, void* sigmask_argpack);
+                            struct __kernel_timespec* tsp, void* sigmask_argpack);
 long libos_syscall_ppoll(struct pollfd* fds, unsigned int nfds, struct timespec* tsp,
                          const __sigset_t* sigmask_ptr, size_t sigsetsize);
 long libos_syscall_set_robust_list(struct robust_list_head* head, size_t len);

libos/src/fs/libos_fs_mem.c

@@ -112,11 +112,9 @@ int mem_file_truncate(struct libos_mem_file* mem, file_off_t size) {
     return 0;
 }
 
-int mem_file_poll(struct libos_mem_file* mem, file_off_t pos, int poll_type) {
-    int ret = 0;
-    if ((poll_type & FS_POLL_RD) && (pos < mem->size))
-        ret |= FS_POLL_RD;
-    if (poll_type & FS_POLL_WR)
-        ret |= FS_POLL_WR;
-    return ret;
+int mem_file_poll(struct libos_mem_file* mem, file_off_t pos, int events, int* out_events) {
+    *out_events = events & (POLLOUT | POLLWRNORM);
+    if ((events & (POLLIN | POLLRDNORM)) && (pos < mem->size))
+        *out_events |= events & (POLLIN | POLLRDNORM);
+    return 0;
 }

libos/src/fs/libos_fs_pseudo.c

@@ -468,26 +468,26 @@ static int pseudo_close(struct libos_handle* hdl) {
     }
 }
 
-static int pseudo_poll(struct libos_handle* hdl, int poll_type) {
+static int pseudo_poll(struct libos_handle* hdl, int events, int* out_events) {
     struct pseudo_node* node = hdl->inode->data;
     switch (node->type) {
         case PSEUDO_STR: {
             assert(hdl->type == TYPE_STR);
             lock(&hdl->pos_lock);
             lock(&hdl->lock);
-            int ret = mem_file_poll(&hdl->info.str.mem, hdl->pos, poll_type);
+            int ret = mem_file_poll(&hdl->info.str.mem, hdl->pos, events, out_events);
             unlock(&hdl->lock);
             unlock(&hdl->pos_lock);
             return ret;
         }
 
         case PSEUDO_DEV: {
-            int ret = 0;
-            if ((poll_type & FS_POLL_RD) && node->dev.dev_ops.read)
-                ret |= FS_POLL_RD;
-            if ((poll_type & FS_POLL_WR) && node->dev.dev_ops.write)
-                ret |= FS_POLL_WR;
-            return ret;
+            *out_events = 0;
+            if ((events & POLLIN) && node->dev.dev_ops.read)
+                *out_events |= POLLIN;
+            if ((events & POLLOUT) && node->dev.dev_ops.write)
+                *out_events |= POLLOUT;
+            return 0;
         }
 
         default:

libos/src/fs/libos_fs_util.c

@@ -116,27 +116,16 @@ file_off_t generic_inode_seek(struct libos_handle* hdl, file_off_t offset, int o
     return ret;
 }
 
-int generic_inode_poll(struct libos_handle* hdl, int poll_type) {
+int generic_inode_poll(struct libos_handle* hdl, int events, int* out_events) {
     int ret;
 
-    lock(&hdl->pos_lock);
-    lock(&hdl->inode->lock);
-
     if (hdl->inode->type == S_IFREG) {
         ret = 0;
-        if (poll_type & FS_POLL_WR)
-            ret |= FS_POLL_WR;
-        /* TODO: The `hdl->pos < hdl->inode->size` condition is wrong, the `poll` syscall treats
-         * end-of-file as readable. Check if removing this condition doesn't break anything
-         * in our `poll` implementation. */
-        if ((poll_type & FS_POLL_RD) && hdl->pos < hdl->inode->size)
-            ret |= FS_POLL_RD;
+        *out_events = events & (POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM);
     } else {
         ret = -EAGAIN;
     }
 
-    unlock(&hdl->inode->lock);
-    unlock(&hdl->pos_lock);
     return ret;
 }