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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); 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) if (cur < max && fcntl(infd, F_SETPIPE_SZ, max) != -1)
cur = max; cur = max;
return (cur); return (cur);

8
man/man8/zfs.8
View File

@ -745,6 +745,14 @@ to use
to mount ZFS datasets. to mount ZFS datasets.
This option is provided for backwards compatibility with older ZFS versions. This option is provided for backwards compatibility with older ZFS versions.
.El .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 .Sh INTERFACE STABILITY
.Sy Committed . .Sy Committed .