Getname flags

• http://lxr.free-electrons.com/source/fs/namei.c#L133

132 static struct filename *
133 getname_flags(const char __user *filename, int flags, int *empty)
134 {
135         struct filename *result, *err;
136         int len;
137         long max;
138         char *kname;
139 
140         result = audit_reusename(filename);  //fill out filename with info from existing entry, audit_name list에 해당 name이 존재하면 name return, 그렇지 않다면 __getname호출
141         if (result)
142                 return result;
143 
144         result = __getname();  //kmem_cache_alloc함수 호출, 코드의 끝에 삽입
145         if (unlikely(!result))
146                 return ERR_PTR(-ENOMEM);  //-ENOMEM is out of memory
147 
148         /*
149          * First, try to embed the struct filename inside the names_cache
150          * allocation
151          */
152         kname = (char *)result + sizeof(*result);
153         result->name = kname;
154         result->separate = false;
155         max = EMBEDDED_NAME_MAX;
156 
157 recopy:
158         len = strncpy_from_user(kname, filename, max);
159         if (unlikely(len < 0)) {
160                 err = ERR_PTR(len);
161                 goto error;
162         }
163 
164         /*
165          * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
166          * separate struct filename so we can dedicate the entire
167          * names_cache allocation for the pathname, and re-do the copy from
168          * userland.
169          */
170         if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
171                 kname = (char *)result;
172 
173                 result = kzalloc(sizeof(*result), GFP_KERNEL);
174                 if (!result) {
175                         err = ERR_PTR(-ENOMEM);
176                         result = (struct filename *)kname;
177                         goto error;
178                 }
179                 result->name = kname;
180                 result->separate = true;
181                 max = PATH_MAX;
182                 goto recopy;
183         }
184 
185         /* The empty path is special. */
186         if (unlikely(!len)) {
187                 if (empty)
188                         *empty = 1;
189                 err = ERR_PTR(-ENOENT);
190                 if (!(flags & LOOKUP_EMPTY))
191                         goto error;
192         }
193 
194         err = ERR_PTR(-ENAMETOOLONG);
195         if (unlikely(len >= PATH_MAX))
196                 goto error;
197 
198         result->uptr = filename;
199         result->aname = NULL;
200         audit_getname(result);
201         return result;
202 
203 error:
204         final_putname(result);
205         return err;
206 }
 
2109 #define __getname()             kmem_cache_alloc(names_cachep, GFP_KERNEL)  //GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS) (=Can wait and reschedule or Can start physical IO? or Can call down to low-level FS?)
 
3456 /**
3457  * kmem_cache_alloc - Allocate an object
3458  * @cachep: The cache to allocate from.
3459  * @flags: See kmalloc().
3460  *
3461  * Allocate an object from this cache.  The flags are only relevant
3462  * if the cache has no available objects.
3463  */
3464 void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
3465 {
3466         void *ret = slab_alloc(cachep, flags, _RET_IP_);
3467 
3468         trace_kmem_cache_alloc(_RET_IP_, ret,
3469                                cachep->object_size, cachep->size, flags);
3470 
3471         return ret;
3472 }
3473 EXPORT_SYMBOL(kmem_cache_alloc);