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Add workaround for broken Linux pipes 

Linux has an unresolved hang if you resize a pipe with bytes
in it.

Since there's no obvious way to detect this happening, added a
workaround to disable resizing the pipe buffer if you set an
environment variable.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #13309
This commit is contained in:
Rich Ercolani 2022-05-09 19:33:55 -04:00 committed by GitHub
parent a18d13c200
commit a30927f763
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13
lib/libzfs_core/libzfs_core.c
View File

@ -607,6 +607,19 @@ max_pipe_buffer(int infd)
}
unsigned int cur = fcntl(infd, F_GETPIPE_SZ);
/*
* Sadly, Linux has an unfixed deadlock if you do SETPIPE_SZ on a pipe
* with data in it.
* cf. #13232, https://bugzilla.kernel.org/show_bug.cgi?id=212295
*
* And since the problem is in waking up the writer, there's nothing
* we can do about it from here.
*
* So if people want to, they can set this, but they
* may regret it...
*/
if (getenv("ZFS_SET_PIPE_MAX") == NULL)
return (cur);
if (cur < max && fcntl(infd, F_SETPIPE_SZ, max) != -1)
cur = max;
return (cur);

8
man/man8/zfs.8
View File

@ -745,6 +745,14 @@ to use
to mount ZFS datasets.
This option is provided for backwards compatibility with older ZFS versions.
.El
.Bl -tag -width "ZFS_SET_PIPE_MAX"
.It Sy ZFS_SET_PIPE_MAX
Tells
.Nm zfs
to set the maximum pipe size for sends/recieves.
Disabled by default on Linux
due to an unfixed deadlock in Linux's pipe size handling code.
.El
.
.Sh INTERFACE STABILITY
.Sy Committed .