fs/sync.c

   1 /*
   2  * High-level sync()-related operations
   3  */
   4
   5 #include <linux/kernel.h>
   6 #include <linux/file.h>
   7 #include <linux/fs.h>
   8 #include <linux/module.h>
   9 #include <linux/writeback.h>
  10 #include <linux/syscalls.h>
  11 #include <linux/linkage.h>
  12 #include <linux/pagemap.h>
  13
  14 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
  15                         SYNC_FILE_RANGE_WAIT_AFTER)
  16
  17 /*
  18  * sys_sync_file_range() permits finely controlled syncing over a segment of
  19  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
  20  * zero then sys_sync_file_range() will operate from offset out to EOF.
  21  *
  22  * The flag bits are:
  23  *
  24  * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
  25  * before performing the write.
  26  *
  27  * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
  28  * range which are not presently under writeback.
  29  *
  30  * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
  31  * after performing the write.
  32  *
  33  * Useful combinations of the flag bits are:
  34  *
  35  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
  36  * in the range which were dirty on entry to sys_sync_file_range() are placed
  37  * under writeout.  This is a start-write-for-data-integrity operation.
  38  *
  39  * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
  40  * are not presently under writeout.  This is an asynchronous flush-to-disk
  41  * operation.  Not suitable for data integrity operations.
  42  *
  43  * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
  44  * completion of writeout of all pages in the range.  This will be used after an
  45  * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
  46  * for that operation to complete and to return the result.
  47  *
  48  * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
  49  * a traditional sync() operation.  This is a write-for-data-integrity operation
  50  * which will ensure that all pages in the range which were dirty on entry to
  51  * sys_sync_file_range() are committed to disk.
  52  *
  53  *
  54  * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
  55  * I/O errors or ENOSPC conditions and will return those to the caller, after
  56  * clearing the EIO and ENOSPC flags in the address_space.
  57  *
  58  * It should be noted that none of these operations write out the file's
  59  * metadata.  So unless the application is strictly performing overwrites of
  60  * already-instantiated disk blocks, there are no guarantees here that the data
  61  * will be available after a crash.
  62  */
  63 asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
  64                                         unsigned int flags)
  65 {
  66         int ret;
  67         struct file *file;
  68         loff_t endbyte;                 /* inclusive */
  69         int fput_needed;
  70         umode_t i_mode;
  71
  72         ret = -EINVAL;
  73         if (flags & ~VALID_FLAGS)
  74                 goto out;
  75
  76         endbyte = offset + nbytes;
  77
  78         if ((s64)offset < 0)
  79                 goto out;
  80         if ((s64)endbyte < 0)
  81                 goto out;
  82         if (endbyte < offset)
  83                 goto out;
  84
  85         if (sizeof(pgoff_t) == 4) {
  86                 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
  87                         /*
  88                          * The range starts outside a 32 bit machine's
  89                          * pagecache addressing capabilities.  Let it "succeed"
  90                          */
  91                         ret = 0;
  92                         goto out;
  93                 }
  94                 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
  95                         /*
  96                          * Out to EOF
  97                          */
  98                         nbytes = 0;
  99                 }
 100         }
 101
 102         if (nbytes == 0)
 103                 endbyte = LLONG_MAX;
 104         else
 105                 endbyte--;              /* inclusive */
 106
 107         ret = -EBADF;
 108         file = fget_light(fd, &fput_needed);
 109         if (!file)
 110                 goto out;
 111
 112         i_mode = file->f_dentry->d_inode->i_mode;
 113         ret = -ESPIPE;
 114         if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
 115                         !S_ISLNK(i_mode))
 116                 goto out_put;
 117
 118         ret = do_sync_file_range(file, offset, endbyte, flags);
 119 out_put:
 120         fput_light(file, fput_needed);
 121 out:
 122         return ret;
 123 }
 124
 125 /*
 126  * `endbyte' is inclusive
 127  */
 128 int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
 129                         unsigned int flags)
 130 {
 131         int ret;
 132         struct address_space *mapping;
 133
 134         mapping = file->f_mapping;
 135         if (!mapping) {
 136                 ret = -EINVAL;
 137                 goto out;
 138         }
 139
 140         ret = 0;
 141         if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 142                 ret = wait_on_page_writeback_range(mapping,
 143                                         offset >> PAGE_CACHE_SHIFT,
 144                                         endbyte >> PAGE_CACHE_SHIFT);
 145                 if (ret < 0)
 146                         goto out;
 147         }
 148
 149         if (flags & SYNC_FILE_RANGE_WRITE) {
 150                 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
 151                                                 WB_SYNC_NONE);
 152                 if (ret < 0)
 153                         goto out;
 154         }
 155
 156         if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
 157                 ret = wait_on_page_writeback_range(mapping,
 158                                         offset >> PAGE_CACHE_SHIFT,
 159                                         endbyte >> PAGE_CACHE_SHIFT);
 160         }
 161 out:
 162         return ret;
 163 }
 164 EXPORT_SYMBOL_GPL(do_sync_file_range);