On 04/16/2014 08:05 AM, Christoph Hellwig wrote: > Michael, can you apply this now that we merged FALLOC_FL_COLLAPSE_RANGE > into the kernel tree? I've applied Namjae Jeon's patch (thanks Namjae!), and done a lot of tweaking to generate the patch below. Along the way I noticed that there is an inconsistency between XFS and JFS that should be fixed (and so have added Dave and Ted to CC, as well as linux-fsdevel@). If 'fd' does not refer to a regular file, then XFS fails with the error EINVAL (fs/xfs/xfs_file.c::xfs_file_fallocate()), but ext4 fails with the error EOPNOTSUP (fs/ext4/extents::ext4_collapse_range()). I suspect that EINVAL is the right error for this case. I'd appreciate review on my revised patch, below. Cheers, Michael diff --git a/man2/fallocate.2 b/man2/fallocate.2 index b31bbde..15d0c2b 100644 --- a/man2/fallocate.2 +++ b/man2/fallocate.2 @@ -124,6 +124,62 @@ Btrfs (since Linux 3.7) .IP * tmpfs (since Linux 3.5) .\" commit 83e4fa9c16e4af7122e31be3eca5d57881d236fe +.SS Collapsing file space +.\" commit 00f5e61998dd17f5375d9dfc01331f104b83f841 +Specifying the +.BR FALLOC_FL_COLLAPSE_RANGE +flag (available since Linux 3.15) in +.I mode +removes a byte range from a file, without leaving a hole. +The byte range to be collapsed starts at +.I offset +and continues for +.I len +bytes. +At the completion of the operation, +the contents of the file starting at the location +.I offset+len +will be appended at the location +.IR offset , +and the file will be +.I len +bytes smaller. + +A filesystem may place limitations on the granularity of the operation, +in order to ensure efficient implementation. +Typically, +.I offset +and +.I len +must be a multiple of the filesystem logical block size, +which varies according to the filesystem type and configuration. +If a filesystem has such a requirement, +.BR fallocate () +will fail with the error +.BR EINVAL +if this requirement is violated. + +If the region specified by +.I offset +plus +.I len +reaches or passes the end of file, an error is returned; +instead, use +.BR ftruncate (2) +to truncate a file. + +No other flags may be specified in +.IR mode +in conjunction with +.BR FALLOC_FL_COLLAPSE_RANGE . + +As at Linux 3.15, +.B FALLOC_FL_COLLAPSE_RANGE +is supported by +ext4 (only for extent-based files) +.\" commit 9eb79482a97152930b113b51dff530aba9e28c8e +and XFS. +.\" commit e1d8fb88a64c1f8094b9f6c3b6d2d9e6719c970d .SH RETURN VALUE On success, .BR fallocate () @@ -156,6 +212,36 @@ was less than 0, or .\" http://thread.gmane.org/gmane.linux.file-systems/48331/focus=1193526 was less than or equal to 0. .TP +.B EINVAL +.I mode +is +.BR FALLOC_FL_COLLAPSE_RANGE +and the range specified by +.I offset +plus +.I len +reaches or passes the end of the file. +.TP +.B EINVAL +.I mode +is +.BR FALLOC_FL_COLLAPSE_RANGE , +but either +.I offset +or +.I len +is not a multiple of the filesystem block size. +.TP +.B EINVAL +mode contains both +.B FALLOC_FL_COLLAPSE_RANGE +and other flags; +no other flags are permitted with +.BR FALLOC_FL_COLLAPSE_RANGE . +.\" FIXME Document error when FALLOC_FL_COLLAPSE_RANGE +.\" is given a nonregular file. As at 3.15-rc1, XFS gives +.\" EINVAL, but ext4 gives EOPNOTSUPP. +.TP .B EIO An I/O error occurred while reading from or writing to a filesystem. .TP @@ -193,6 +279,8 @@ Or: .I mode specifies .BR FALLOC_FL_PUNCH_HOLE +or +.BR FALLOC_FL_COLLAPSE_RANGE and the file referred to by .I fd @@ -203,6 +291,14 @@ is marked append-only .B ESPIPE .I fd refers to a pipe or FIFO. +.TP +.B ETXTBSY +.I mode +specifies +.BR FALLOC_FL_COLLAPSE_RANGE , +but the file referred to by +.IR fd +is currently being executed. .SH VERSIONS .BR fallocate () is available on Linux since kernel 2.6.23. -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
