diff options
| -rw-r--r-- | block/file-posix.c | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/block/file-posix.c b/block/file-posix.c index 7583bbfbb3..07bb061fe4 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2076,6 +2076,7 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp) { BlockdevCreateOptionsFile *file_opts; int fd; + int perm, shared; int result = 0; /* Validate options and set default values */ @@ -2090,14 +2091,44 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp) } /* Create file */ - fd = qemu_open(file_opts->filename, O_RDWR | O_CREAT | O_TRUNC | O_BINARY, - 0644); + fd = qemu_open(file_opts->filename, O_RDWR | O_CREAT | O_BINARY, 0644); if (fd < 0) { result = -errno; error_setg_errno(errp, -result, "Could not create file"); goto out; } + /* Take permissions: We want to discard everything, so we need + * BLK_PERM_WRITE; and truncation to the desired size requires + * BLK_PERM_RESIZE. + * On the other hand, we cannot share the RESIZE permission + * because we promise that after this function, the file has the + * size given in the options. If someone else were to resize it + * concurrently, we could not guarantee that. + * Note that after this function, we can no longer guarantee that + * the file is not touched by a third party, so it may be resized + * then. */ + perm = BLK_PERM_WRITE | BLK_PERM_RESIZE; + shared = BLK_PERM_ALL & ~BLK_PERM_RESIZE; + + /* Step one: Take locks */ + result = raw_apply_lock_bytes(fd, perm, shared, false, errp); + if (result < 0) { + goto out_close; + } + + /* Step two: Check that nobody else has taken conflicting locks */ + result = raw_check_lock_bytes(fd, perm, shared, errp); + if (result < 0) { + goto out_close; + } + + /* Clear the file by truncating it to 0 */ + result = raw_regular_truncate(fd, 0, PREALLOC_MODE_OFF, errp); + if (result < 0) { + goto out_close; + } + if (file_opts->nocow) { #ifdef __linux__ /* Set NOCOW flag to solve performance issue on fs like btrfs. @@ -2113,6 +2144,8 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp) #endif } + /* Resize and potentially preallocate the file to the desired + * final size */ result = raw_regular_truncate(fd, file_opts->size, file_opts->preallocation, errp); if (result < 0) { |