Add a new operation mode to fallocate, called FALLOC_FL_ZERO_RANGE. It resembles the similarly named XFS ioctl. Filesystems should preallocate blocks for regions that span holes in the file, and convert the entire range to unwritten extents. This operation is a fast method of overwriting any from the range specified with zeros without removing any blocks or having to write zeros to disk. Any subsequent read in the given range will return zeros until new data is written. This functionality requires filesystems to support unwritten extents. If xfs_info(8) reports unwritten=1, then the filesystem was made to flag unwritten extents. It is okay to report EOPNOTSUPP and let the application deal with the outcome, but it is not okay to succeed or report EOPNOTSUPP for the same inode depending on the other arguments. FALLOC_FL_PUNCH_HOLE|FALLOC_FL_ZERO_RANGE is ruled out here, at the vfs level, rather than leaving it to the filesystems. This way, in the future 0x6 could be used as a third mode. Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> --- fs/open.c | 8 +++++++- include/linux/falloc.h | 1 + 2 files changed, 8 insertions(+), 1 deletions(-) diff --git a/fs/open.c b/fs/open.c index d6c79a0..dd812b3 100644 --- a/fs/open.c +++ b/fs/open.c @@ -222,8 +222,14 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len) if (offset < 0 || len <= 0) return -EINVAL; + /* Punch hole and write-zeroes are mutually exclusive */ + if ((mode & FALLOC_FL_PUNCH_HOLE) && + (mode & FALLOC_FL_ZERO_RANGE)) + return -EINVAL; + /* Return error if mode is not supported */ - if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) + if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | + FALLOC_FL_ZERO_RANGE)) return -EOPNOTSUPP; /* Punch hole must have keep size set */ diff --git a/include/linux/falloc.h b/include/linux/falloc.h index 73e0b62..9aa9599 100644 --- a/include/linux/falloc.h +++ b/include/linux/falloc.h @@ -3,6 +3,7 @@ #define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend size */ #define FALLOC_FL_PUNCH_HOLE 0x02 /* de-allocates range */ +#define FALLOC_FL_ZERO_RANGE 0x04 /* write zeroes */ #ifdef __KERNEL__ -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
