On Thu, 2017-09-28 at 13:01 +1000, NeilBrown wrote: > On Thu, Sep 14 2017, Jeff Layton wrote: > > > > .TP > > > .B EIO > > > -An error occurred during synchronization. > > > +An error occurred during synchronization. This error may relate > > > +to data written to some other file descriptor on the same file. > > > +.\" commit 088737f44bbf6378745f5b57b035e57ee3dc4750 > > > +Since Linux 4.13 errors from write-back will be reported to > > > +all file descriptors that might have written the data which > > > triggered > > > +the error, and which are still open. > > > > This is a little awkward. How could we report to a fd that was no > > longer > > open? How about: > > > > "Since Linux 4.13, errors from write-back will be reported to all > > file > > descriptors that were open at the time that the error was > > recorded." > > That might be simpler, but it is less correct. As I go on to say, > NFS > *doesn't* report on all file descriptors that were open at that time. > > I've changed it to > > ------------------- > Since Linux 4.13, errors from write-back will be reported to > all file descriptors that might have written the data which triggered > the error. Some filesystems (e.g. NFS) keep close track of which > data > came through which file descriptor, and give precise reporting. > Other filesystems (e.g. most local filesystems) will report errors to > all file descriptors that where open on the file when the error was > recorded. > ------------------ > > which includes some of your text, and removes the "that are still > open" > which probably doesn't help. > > > > .TP > > > .B EIO > > > A low-level I/O error occurred while modifying the inode. > > > +This error may relate to data written by an earlier > > > +.BR write (2), > > > +which may have been issued to a different file descriptor on > > > +the same file. Since Linux 4.13 errors from write-back will > > > +be reported to all file descriptors that might have > > > +written the data which triggered the error, and which are still > > > +open. > > > > > > This is where things get a little more vague. > > > > Some filesystems will return errors on a subsequent write(2) when > > previous writeback has failed -- some don't. In either case though, > > write(2) should never advance your errseq_t cursor, so only an > > fsync > > will "clear" an earlier error. > > > > I'm not sure how best to convey that in the manpages though. > > How about: > > ------------- > This error may relate to the write-back of data written by an > earlier > .BR write (2), > which may have been issued to a different file descriptor on > the same file. Since Linux 4.13, errors from write-back come > with a promise that they > .I may > be reported by subsequent. > .BR write (2) > requests, and > .I will > be reported by a subsequent > .BR fsync (2) > (whether or not they were also reported by > .BR write (2)). > ------------ > ?? > > Those changes are included in the following. > > Thanks, > NeilBrown > > From: NeilBrown <neilb@xxxxxxxx> > Date: Thu, 14 Sep 2017 09:44:43 +1000 > Subject: [PATCH] write.2, fsync.2, close.2: update description of > error codes > > Since 4.13, errors from writeback are more reliably reported > to all file descriptors that might be relevant. > > Add notes to this effect, and also add detail about ENOSPC and EDQUOT > which can be delayed in a similar many to EIO - for NFS in > particular. > > Signed-off-by: NeilBrown <neilb@xxxxxxxx> > --- > man2/close.2 | 9 +++++++++ > man2/fsync.2 | 18 +++++++++++++++++- > man2/write.2 | 28 +++++++++++++++++++++++++--- > 3 files changed, 51 insertions(+), 4 deletions(-) > > diff --git a/man2/close.2 b/man2/close.2 > index 55d89ed3dbc7..136bd0be3f67 100644 > --- a/man2/close.2 > +++ b/man2/close.2 > @@ -82,6 +82,15 @@ call was interrupted by a signal; see > .TP > .B EIO > An I/O error occurred. > +.TP > +.BR ENOSPC ", " EDQUOT > +On NFS, these errors are not normally reported against the first > write > +which exceeds the available storage space, but instead against a > +subsequent > +.BR write (2), > +.BR fsync (2), > +or > +.BR close (2). > .PP > See NOTES for a discussion of why > .BR close () > diff --git a/man2/fsync.2 b/man2/fsync.2 > index eed3c460bea9..c7878bf3496f 100644 > --- a/man2/fsync.2 > +++ b/man2/fsync.2 > @@ -121,7 +121,15 @@ is set appropriately. > is not a valid open file descriptor. > .TP > .B EIO > -An error occurred during synchronization. > +An error occurred during synchronization. This error may relate > +to data written to some other file descriptor on the same file. > +.\" commit 088737f44bbf6378745f5b57b035e57ee3dc4750 > +Since Linux 4.13, errors from write-back will be reported to > +all file descriptors that might have written the data which > triggered > +the error. Some filesystems (e.g. NFS) keep close track of which > data > +came through which file descriptor, and give more precise reporting. > +Other filesystems (e.g. most local filesystems) will report errors > to > +all file descriptors that where open on the file when the error was > recorded. > .TP > .B ENOSPC > Disk space was exhausted while synchronizing. > @@ -130,6 +138,14 @@ Disk space was exhausted while synchronizing. > .I fd > is bound to a special file (e.g., a pipe, FIFO, or socket) > which does not support synchronization. > +.TP > +.BR ENOSPC ", " EDQUOT > +.I fd > +is bound to a file on NFS or another filesystem which does not > allocate > +space at the time of a > +.BR write (2) > +system call, and some previous write failed due to insufficient > +storage space. > .SH CONFORMING TO > POSIX.1-2001, POSIX.1-2008, 4.3BSD. > .SH AVAILABILITY > diff --git a/man2/write.2 b/man2/write.2 > index 061aa70cf590..b1cc3a2cfb17 100644 > --- a/man2/write.2 > +++ b/man2/write.2 > @@ -47,7 +47,7 @@ write \- write to a file descriptor > .BR write () > writes up to > .I count > -bytes from the buffer pointed > +bytes from the buffer starting at > .I buf > to the file referred to by the file descriptor > .IR fd . > @@ -181,6 +181,22 @@ or the file offset is not suitably aligned. > .TP > .B EIO > A low-level I/O error occurred while modifying the inode. > +This error may relate to the write-back of data written by an > +earlier > +.BR write (2), > +which may have been issued to a different file descriptor on > +the same file. Since Linux 4.13, errors from write-back come > +with a promise that they > +.I may > +be reported by subsequent. > +.BR write (2) > +requests, and > +.I will > +be reported by a subsequent > +.BR fsync (2) > +(whether or not they were also reported by > +.BR write (2)). > +.\" commit 088737f44bbf6378745f5b57b035e57ee3dc4750 > .TP > .B ENOSPC > The device containing the file referred to by > @@ -222,8 +238,14 @@ unsigned and signed integer data types specified > by POSIX.1. > A successful return from > .BR write () > does not make any guarantee that data has been committed to disk. > -In fact, on some buggy implementations, it does not even guarantee > -that space has successfully been reserved for the data. > +On some filesystems, including NFS, it does not even guarantee > +that space has successfully been reserved for the data. In the > case, > +some errors might be delayed to a future > +.BR write (2) > +or to > +.BR fsync (2) > +or even > +.BR close (2). > The only way to be sure is to call > .BR fsync (2) > after you are done writing all your data. Looks good to me! Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
