lib/libsffs/write.c

   1 /* This file contains file writing system call handlers.
   2  *
   3  * The entry points into this file are:
   4  *   do_write           perform the WRITE file system call
   5  *   do_ftrunc          perform the FTRUNC file system call
   6  *
   7  * Created:
   8  *   April 2009 (D.C. van Moolenbroek)
   9  */
  10
  11 #include "inc.h"
  12
  13 static int write_file(struct inode *ino, u64_t *posp, size_t *countp,
  14         cp_grant_id_t *grantp);
  15
  16 /*===========================================================================*
  17  *                              write_file                                   *
  18  *===========================================================================*/
  19 static int write_file(struct inode *ino, u64_t *posp, size_t *countp,
  20         cp_grant_id_t *grantp)
  21 {
  22 /* Write data or zeroes to a file, depending on whether a valid pointer to
  23  * a data grant was provided.
  24  */
  25   u64_t pos;
  26   size_t count, size;
  27   vir_bytes off;
  28   char *ptr;
  29   int r, chunk;
  30
  31   assert(!IS_DIR(ino));
  32
  33   if ((r = get_handle(ino)) != OK)
  34         return r;
  35
  36   pos = *posp;
  37   count = *countp;
  38
  39   assert(count > 0);
  40
  41   /* Use the buffer from below to eliminate extra copying. */
  42   size = sffs_table->t_writebuf(&ptr);
  43   off = 0;
  44
  45   while (count > 0) {
  46         chunk = MIN(count, size);
  47
  48         if (grantp != NULL) {
  49                 r = sys_safecopyfrom(m_in.m_source, *grantp,
  50                         off, (vir_bytes) ptr, chunk);
  51
  52                 if (r != OK)
  53                         break;
  54         } else {
  55                 /* Do this every time. We don't know what happens below. */
  56                 memset(ptr, 0, chunk);
  57         }
  58
  59         if ((r = sffs_table->t_write(ino->i_file, ptr, chunk, pos)) <= 0)
  60                 break;
  61
  62         count -= r;
  63         off += r;
  64         pos += r;
  65   }
  66
  67   if (r < 0)
  68         return r;
  69
  70   *posp = pos;
  71   *countp = off;
  72
  73   return OK;
  74 }
  75
  76 /*===========================================================================*
  77  *                              do_write                                     *
  78  *===========================================================================*/
  79 int do_write(void)
  80 {
  81 /* Write data to a file.
  82  */
  83   struct inode *ino;
  84   u64_t pos;
  85   size_t count;
  86   cp_grant_id_t grant;
  87   int r;
  88
  89   if (state.s_read_only)
  90         return EROFS;
  91
  92   if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
  93         return EINVAL;
  94
  95   if (IS_DIR(ino)) return EISDIR;
  96
  97   pos = m_in.REQ_SEEK_POS;
  98   count = m_in.REQ_NBYTES;
  99   grant = m_in.REQ_GRANT;
 100
 101   if (count == 0) return EINVAL;
 102
 103   if ((r = write_file(ino, &pos, &count, &grant)) != OK)
 104         return r;
 105
 106   m_out.RES_SEEK_POS = pos;
 107   m_out.RES_NBYTES = count;
 108
 109   return OK;
 110 }
 111
 112 /*===========================================================================*
 113  *                              do_ftrunc                                    *
 114  *===========================================================================*/
 115 int do_ftrunc(void)
 116 {
 117 /* Change file size or create file holes.
 118  */
 119   char path[PATH_MAX];
 120   struct inode *ino;
 121   struct sffs_attr attr;
 122   u64_t start, end, delta;
 123   size_t count;
 124   int r;
 125
 126   if (state.s_read_only)
 127         return EROFS;
 128
 129   if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
 130         return EINVAL;
 131
 132   if (IS_DIR(ino)) return EISDIR;
 133
 134   start = m_in.REQ_TRC_START;
 135   end = m_in.REQ_TRC_END;
 136
 137   if (end == 0) {
 138         /* Truncate or expand the file. */
 139         if ((r = verify_inode(ino, path, NULL)) != OK)
 140                 return r;
 141
 142         attr.a_mask = SFFS_ATTR_SIZE;
 143         attr.a_size = start;
 144
 145         r = sffs_table->t_setattr(path, &attr);
 146   } else {
 147         /* Write zeroes to the file. We can't create holes. */
 148         if (end <= start) return EINVAL;
 149
 150         delta = end - start;
 151
 152         if (ex64hi(delta) != 0) return EINVAL;
 153
 154         count = ex64lo(delta);
 155
 156         r = write_file(ino, &start, &count, NULL);
 157   }
 158
 159   return r;
 160 }