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(ino, posp, countp, grantp)
  20 struct inode *ino;
  21 u64_t *posp;
  22 size_t *countp;
  23 cp_grant_id_t *grantp;
  24 {
  25 /* Write data or zeroes to a file, depending on whether a valid pointer to
  26  * a data grant was provided.
  27  */
  28   u64_t pos;
  29   size_t count, size;
  30   vir_bytes off;
  31   char *ptr;
  32   int r, chunk;
  33
  34   assert(!IS_DIR(ino));
  35
  36   if ((r = get_handle(ino)) != OK)
  37         return r;
  38
  39   pos = *posp;
  40   count = *countp;
  41
  42   assert(count > 0);
  43
  44   /* Use the buffer from below to eliminate extra copying. */
  45   size = sffs_table->t_writebuf(&ptr);
  46   off = 0;
  47
  48   while (count > 0) {
  49         chunk = MIN(count, size);
  50
  51         if (grantp != NULL) {
  52                 r = sys_safecopyfrom(m_in.m_source, *grantp,
  53                         off, (vir_bytes) ptr, chunk);
  54
  55                 if (r != OK)
  56                         break;
  57         } else {
  58                 /* Do this every time. We don't know what happens below. */
  59                 memset(ptr, 0, chunk);
  60         }
  61
  62         if ((r = sffs_table->t_write(ino->i_file, ptr, chunk, pos)) <= 0)
  63                 break;
  64
  65         count -= r;
  66         off += r;
  67         pos = add64u(pos, r);
  68   }
  69
  70   if (r < 0)
  71         return r;
  72
  73   *posp = pos;
  74   *countp = off;
  75
  76   return OK;
  77 }
  78
  79 /*===========================================================================*
  80  *                              do_write                                     *
  81  *===========================================================================*/
  82 int do_write()
  83 {
  84 /* Write data to a file.
  85  */
  86   struct inode *ino;
  87   u64_t pos;
  88   size_t count;
  89   cp_grant_id_t grant;
  90   int r;
  91
  92   if (state.s_read_only)
  93         return EROFS;
  94
  95   if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
  96         return EINVAL;
  97
  98   if (IS_DIR(ino)) return EISDIR;
  99
 100   pos = make64(m_in.REQ_SEEK_POS_LO, m_in.REQ_SEEK_POS_HI);
 101   count = m_in.REQ_NBYTES;
 102   grant = m_in.REQ_GRANT;
 103
 104   if (count == 0) return EINVAL;
 105
 106   if ((r = write_file(ino, &pos, &count, &grant)) != OK)
 107         return r;
 108
 109   m_out.RES_SEEK_POS_HI = ex64hi(pos);
 110   m_out.RES_SEEK_POS_LO = ex64lo(pos);
 111   m_out.RES_NBYTES = count;
 112
 113   return OK;
 114 }
 115
 116 /*===========================================================================*
 117  *                              do_ftrunc                                    *
 118  *===========================================================================*/
 119 int do_ftrunc()
 120 {
 121 /* Change file size or create file holes.
 122  */
 123   char path[PATH_MAX];
 124   struct inode *ino;
 125   struct sffs_attr attr;
 126   u64_t start, end, delta;
 127   size_t count;
 128   int r;
 129
 130   if (state.s_read_only)
 131         return EROFS;
 132
 133   if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
 134         return EINVAL;
 135
 136   if (IS_DIR(ino)) return EISDIR;
 137
 138   start = make64(m_in.REQ_TRC_START_LO, m_in.REQ_TRC_START_HI);
 139   end = make64(m_in.REQ_TRC_END_LO, m_in.REQ_TRC_END_HI);
 140
 141   if (cmp64u(end, 0) == 0) {
 142         /* Truncate or expand the file. */
 143         if ((r = verify_inode(ino, path, NULL)) != OK)
 144                 return r;
 145
 146         attr.a_mask = SFFS_ATTR_SIZE;
 147         attr.a_size = start;
 148
 149         r = sffs_table->t_setattr(path, &attr);
 150   } else {
 151         /* Write zeroes to the file. We can't create holes. */
 152         if (cmp64(end, start) <= 0) return EINVAL;
 153
 154         delta = sub64(end, start);
 155
 156         if (ex64hi(delta) != 0) return EINVAL;
 157
 158         count = ex64lo(delta);
 159
 160         r = write_file(ino, &start, &count, NULL);
 161   }
 162
 163   return r;
 164 }