Upon a successful copy, return true. If the initial extent scan
fails, set *NORMAL_COPY_REQUIRED to true and return false.
Upon any other failure, set *NORMAL_COPY_REQUIRED to false and
- return false. */
+ return false.
+
+ FIXME: Once we no longer need to support Linux kernel versions
+ before 3.1 (2011), this function can be retired as it is superseded
+ by lseek_copy. That is, we no longer need extent-scan.h and can
+ remove any of the code that uses it. */
static bool
extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
size_t hole_size, off_t src_total_size,
return true;
}
+#ifdef SEEK_HOLE
+/* Perform an efficient extent copy, if possible. This avoids
+ the overhead of detecting holes in hole-introducing/preserving
+ copy, and thus makes copying sparse files much more efficient.
+ Copy from SRC_FD to DEST_FD, using BUF (of size BUF_SIZE) for a buffer.
+ Look for holes of size HOLE_SIZE in the input.
+ The input file is of size SRC_TOTAL_SIZE.
+ Use SPARSE_MODE to determine whether to create holes in the output.
+ SRC_NAME and DST_NAME are the input and output file names.
+ Return true if successful, false (with a diagnostic) otherwise. */
+
+static bool
+lseek_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
+ size_t hole_size, off_t ext_start, off_t src_total_size,
+ enum Sparse_type sparse_mode,
+ char const *src_name, char const *dst_name)
+{
+ off_t last_ext_start = 0;
+ off_t last_ext_len = 0;
+ off_t dest_pos = 0;
+ bool wrote_hole_at_eof = true;
+
+ while (0 <= ext_start)
+ {
+ off_t ext_end = lseek (src_fd, ext_start, SEEK_HOLE);
+ if (ext_end < 0)
+ {
+ if (errno != ENXIO)
+ goto cannot_lseek;
+ ext_end = src_total_size;
+ if (ext_end <= ext_start)
+ {
+ /* The input file grew; get its current size. */
+ src_total_size = lseek (src_fd, 0, SEEK_END);
+ if (src_total_size < 0)
+ goto cannot_lseek;
+
+ /* If the input file shrank after growing, stop copying. */
+ if (src_total_size <= ext_start)
+ break;
+
+ ext_end = src_total_size;
+ }
+ }
+ /* If the input file must have grown, increase its measured size. */
+ if (src_total_size < ext_end)
+ src_total_size = ext_end;
+
+ if (lseek (src_fd, ext_start, SEEK_SET) < 0)
+ goto cannot_lseek;
+
+ wrote_hole_at_eof = false;
+ off_t ext_hole_size = ext_start - last_ext_start - last_ext_len;
+
+ if (ext_hole_size)
+ {
+ if (sparse_mode != SPARSE_NEVER)
+ {
+ if (! create_hole (dest_fd, dst_name,
+ sparse_mode == SPARSE_ALWAYS,
+ ext_hole_size))
+ return false;
+ wrote_hole_at_eof = true;
+ }
+ else
+ {
+ /* When not inducing holes and when there is a hole between
+ the end of the previous extent and the beginning of the
+ current one, write zeros to the destination file. */
+ if (! write_zeros (dest_fd, ext_hole_size))
+ {
+ error (0, errno, _("%s: write failed"),
+ quotef (dst_name));
+ return false;
+ }
+ }
+ }
+
+ off_t ext_len = ext_end - ext_start;
+ last_ext_start = ext_start;
+ last_ext_len = ext_len;
+
+ /* Copy this extent, looking for further opportunities to not
+ bother to write zeros unless --sparse=never, since SEEK_HOLE
+ is conservative and may miss some holes. */
+ off_t n_read;
+ bool read_hole;
+ if ( ! sparse_copy (src_fd, dest_fd, buf, buf_size,
+ sparse_mode == SPARSE_NEVER ? 0 : hole_size,
+ true, src_name, dst_name, ext_len, &n_read,
+ &read_hole))
+ return false;
+
+ dest_pos = ext_start + n_read;
+ if (n_read)
+ wrote_hole_at_eof = read_hole;
+ if (n_read < ext_len)
+ {
+ /* The input file shrank. */
+ src_total_size = dest_pos;
+ break;
+ }
+
+ ext_start = lseek (src_fd, dest_pos, SEEK_DATA);
+ if (ext_start < 0)
+ {
+ if (errno != ENXIO)
+ goto cannot_lseek;
+ break;
+ }
+ }
+
+ /* When the source file ends with a hole, we have to do a little more work,
+ since the above copied only up to and including the final extent.
+ In order to complete the copy, we may have to insert a hole or write
+ zeros in the destination corresponding to the source file's hole-at-EOF.
+
+ In addition, if the final extent was a block of zeros at EOF and we've
+ just converted them to a hole in the destination, we must call ftruncate
+ here in order to record the proper length in the destination. */
+ if ((dest_pos < src_total_size || wrote_hole_at_eof)
+ && ! (sparse_mode == SPARSE_NEVER
+ ? write_zeros (dest_fd, src_total_size - dest_pos)
+ : ftruncate (dest_fd, src_total_size) == 0))
+ {
+ error (0, errno, _("failed to extend %s"), quoteaf (dst_name));
+ return false;
+ }
+
+ if (sparse_mode == SPARSE_ALWAYS && dest_pos < src_total_size
+ && punch_hole (dest_fd, dest_pos, src_total_size - dest_pos) < 0)
+ {
+ error (0, errno, _("error deallocating %s"), quoteaf (dst_name));
+ return false;
+ }
+
+ return true;
+
+ cannot_lseek:
+ error (0, errno, _("cannot lseek %s"), quoteaf (src_name));
+ return false;
+}
+#endif
+
/* FIXME: describe */
/* FIXME: rewrite this to use a hash table so we avoid the quadratic
performance hit that's probably noticeable only on trees deeper
/* Type of scan being done on the input when looking for sparseness. */
enum scantype
{
+ /* An error was found when determining scantype. */
+ ERROR_SCANTYPE,
+
/* No fancy scanning; just read and write. */
PLAIN_SCANTYPE,
attempting to create sparse output. */
ZERO_SCANTYPE,
+ /* lseek information is available. */
+ LSEEK_SCANTYPE,
+
/* Extent information is available. */
EXTENT_SCANTYPE
};
-/* Use a heuristic to determine whether stat buffer SB comes from a file
- with sparse blocks. If the file has fewer blocks than would normally
- be needed for a file of its size, then at least one of the blocks in
- the file is a hole. In that case, return true. */
+/* Result of infer_scantype. */
+union scan_inference
+{
+ /* Used if infer_scantype returns LSEEK_SCANTYPE. This is the
+ offset of the first data block, or -1 if the file has no data. */
+ off_t ext_start;
+
+ /* Used if infer_scantype returns EXTENT_SCANTYPE. */
+ struct extent_scan extent_scan;
+};
+
+/* Return how to scan a file with descriptor FD and stat buffer SB.
+ Store any information gathered into *SCAN. */
static enum scantype
-infer_scantype (int fd, struct stat const *sb, struct extent_scan *scan)
+infer_scantype (int fd, struct stat const *sb,
+ union scan_inference *scan_inference)
{
if (! (HAVE_STRUCT_STAT_ST_BLOCKS
&& S_ISREG (sb->st_mode)
&& ST_NBLOCKS (*sb) < sb->st_size / ST_NBLOCKSIZE))
return PLAIN_SCANTYPE;
+#ifdef SEEK_HOLE
+ scan_inference->ext_start = lseek (fd, 0, SEEK_DATA);
+ if (0 <= scan_inference->ext_start)
+ return LSEEK_SCANTYPE;
+ else if (errno != EINVAL && errno != ENOTSUP)
+ return errno == ENXIO ? LSEEK_SCANTYPE : ERROR_SCANTYPE;
+#endif
+
+ struct extent_scan *scan = &scan_inference->extent_scan;
extent_scan_init (fd, scan);
extent_scan_read (scan);
return scan->initial_scan_failed ? ZERO_SCANTYPE : EXTENT_SCANTYPE;
mode_t src_mode = src_sb->st_mode;
struct stat sb;
struct stat src_open_sb;
- struct extent_scan scan;
+ union scan_inference scan_inference;
bool return_val = true;
bool data_copy_required = x->data_copy_required;
size_t buf_size = io_blksize (sb);
size_t hole_size = ST_BLKSIZE (sb);
- fdadvise (source_desc, 0, 0, FADVISE_SEQUENTIAL);
-
/* Deal with sparse files. */
enum scantype scantype = infer_scantype (source_desc, &src_open_sb,
- &scan);
+ &scan_inference);
+ if (scantype == ERROR_SCANTYPE)
+ {
+ error (0, errno, _("cannot lseek %s"), quoteaf (src_name));
+ return_val = false;
+ goto close_src_and_dst_desc;
+ }
bool make_holes
= (S_ISREG (sb.st_mode)
&& (x->sparse_mode == SPARSE_ALWAYS
|| (x->sparse_mode == SPARSE_AUTO
&& scantype != PLAIN_SCANTYPE)));
+ fdadvise (source_desc, 0, 0, FADVISE_SEQUENTIAL);
+
/* If not making a sparse file, try to use a more-efficient
buffer size. */
if (! make_holes)
? extent_copy (source_desc, dest_desc, buf, buf_size, hole_size,
src_open_sb.st_size,
make_holes ? x->sparse_mode : SPARSE_NEVER,
- src_name, dst_name, &scan)
+ src_name, dst_name, &scan_inference.extent_scan)
+#ifdef SEEK_HOLE
+ : scantype == LSEEK_SCANTYPE
+ ? lseek_copy (source_desc, dest_desc, buf, buf_size, hole_size,
+ scan_inference.ext_start, src_open_sb.st_size,
+ make_holes ? x->sparse_mode : SPARSE_NEVER,
+ src_name, dst_name)
+#endif
: sparse_copy (source_desc, dest_desc, buf, buf_size,
make_holes ? hole_size : 0,
x->sparse_mode == SPARSE_ALWAYS,
projects / thirdparty / coreutils.git / commitdiff
