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Cygwin: pwrite(2): sparsify file 

write(2) sparsifies a file after an lseek far enough beyond EOF.

Let pwrite(2) sparsify as well if offset is far enough beyond EOF.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2023-11-27 22:48:50 +01:00
parent 114f89caff
commit f64f3eced8
1 changed files with 20 additions and 0 deletions
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20
winsup/cygwin/fhandler/disk_file.cc
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@ -1724,6 +1724,7 @@ fhandler_disk_file::pwrite (void *buf, size_t count, off_t offset, void *aio)
{
NTSTATUS status;
IO_STATUS_BLOCK io;
FILE_STANDARD_INFORMATION fsi;
LARGE_INTEGER off = { QuadPart:offset };
HANDLE evt = aio ? (HANDLE) aiocb->aio_wincb.event : NULL;
PIO_STATUS_BLOCK pio = aio ? (PIO_STATUS_BLOCK) &aiocb->aio_wincb : &io;
@ -1732,6 +1733,25 @@ fhandler_disk_file::pwrite (void *buf, size_t count, off_t offset, void *aio)
if (prw_handle && (prw_handle_isasync != !!aio))
NtClose (prw_handle), prw_handle = NULL;
/* If the file system supports sparse files and the application is
writing beyond EOF spanning more than one sparsifiable chunk,
convert the file to a sparse file. */
if (pc.support_sparse ()
&& !has_attribute (FILE_ATTRIBUTE_SPARSE_FILE)
&& NT_SUCCESS (NtQueryInformationFile (get_handle (),
&io, &fsi, sizeof fsi,
FileStandardInformation))
&& offset >= fsi.EndOfFile.QuadPart + (128 * 1024))
{
NTSTATUS status;
status = NtFsControlFile (get_handle (), NULL, NULL, NULL,
&io, FSCTL_SET_SPARSE, NULL, 0, NULL, 0);
if (NT_SUCCESS (status))
pc.file_attributes (pc.file_attributes ()
| FILE_ATTRIBUTE_SPARSE_FILE);
debug_printf ("%y = NtFsControlFile(%S, FSCTL_SET_SPARSE)",
status, pc.get_nt_native_path ());
}
if (!prw_handle && prw_open (true, aio))
goto non_atomic;
status = NtWriteFile (prw_handle, evt, NULL, NULL, pio, buf, count,