Fix kernel-doc warnings in struct pipe_inode_info after @wait was
split into @rd_wait and @wr_wait.
include/linux/pipe_fs_i.h:66: warning: Function parameter or member 'rd_wait' not described in 'pipe_inode_info'
include/linux/pipe_fs_i.h:66: warning: Function parameter or member 'wr_wait' not described in 'pipe_inode_info'
Fixes: 0ddad21d3e ("pipe: use exclusive waits when reading or writing")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This makes the pipe code use separate wait-queues and exclusive waiting
for readers and writers, avoiding a nasty thundering herd problem when
there are lots of readers waiting for data on a pipe (or, less commonly,
lots of writers waiting for a pipe to have space).
While this isn't a common occurrence in the traditional "use a pipe as a
data transport" case, where you typically only have a single reader and
a single writer process, there is one common special case: using a pipe
as a source of "locking tokens" rather than for data communication.
In particular, the GNU make jobserver code ends up using a pipe as a way
to limit parallelism, where each job consumes a token by reading a byte
from the jobserver pipe, and releases the token by writing a byte back
to the pipe.
This pattern is fairly traditional on Unix, and works very well, but
will waste a lot of time waking up a lot of processes when only a single
reader needs to be woken up when a writer releases a new token.
A simplified test-case of just this pipe interaction is to create 64
processes, and then pass a single token around between them (this
test-case also intentionally passes another token that gets ignored to
test the "wake up next" logic too, in case anybody wonders about it):
#include <unistd.h>
int main(int argc, char **argv)
{
int fd[2], counters[2];
pipe(fd);
counters[0] = 0;
counters[1] = -1;
write(fd[1], counters, sizeof(counters));
/* 64 processes */
fork(); fork(); fork(); fork(); fork(); fork();
do {
int i;
read(fd[0], &i, sizeof(i));
if (i < 0)
continue;
counters[0] = i+1;
write(fd[1], counters, (1+(i & 1)) *sizeof(int));
} while (counters[0] < 1000000);
return 0;
}
and in a perfect world, passing that token around should only cause one
context switch per transfer, when the writer of a token causes a
directed wakeup of just a single reader.
But with the "writer wakes all readers" model we traditionally had, on
my test box the above case causes more than an order of magnitude more
scheduling: instead of the expected ~1M context switches, "perf stat"
shows
231,852.37 msec task-clock # 15.857 CPUs utilized
11,250,961 context-switches # 0.049 M/sec
616,304 cpu-migrations # 0.003 M/sec
1,648 page-faults # 0.007 K/sec
1,097,903,998,514 cycles # 4.735 GHz
120,781,778,352 instructions # 0.11 insn per cycle
27,997,056,043 branches # 120.754 M/sec
283,581,233 branch-misses # 1.01% of all branches
14.621273891 seconds time elapsed
0.018243000 seconds user
3.611468000 seconds sys
before this commit.
After this commit, I get
5,229.55 msec task-clock # 3.072 CPUs utilized
1,212,233 context-switches # 0.232 M/sec
103,951 cpu-migrations # 0.020 M/sec
1,328 page-faults # 0.254 K/sec
21,307,456,166 cycles # 4.074 GHz
12,947,819,999 instructions # 0.61 insn per cycle
2,881,985,678 branches # 551.096 M/sec
64,267,015 branch-misses # 2.23% of all branches
1.702148350 seconds time elapsed
0.004868000 seconds user
0.110786000 seconds sys
instead. Much better.
[ Note! This kernel improvement seems to be very good at triggering a
race condition in the make jobserver (in GNU make 4.2.1) for me. It's
a long known bug that was fixed back in June 2017 by GNU make commit
b552b0525198 ("[SV 51159] Use a non-blocking read with pselect to
avoid hangs.").
But there wasn't a new release of GNU make until 4.3 on Jan 19 2020,
so a number of distributions may still have the buggy version. Some
have backported the fix to their 4.2.1 release, though, and even
without the fix it's quite timing-dependent whether the bug actually
is hit. ]
Josh Triplett says:
"I've been hammering on your pipe fix patch (switching to exclusive
wait queues) for a month or so, on several different systems, and I've
run into no issues with it. The patch *substantially* improves
parallel build times on large (~100 CPU) systems, both with parallel
make and with other things that use make's pipe-based jobserver.
All current distributions (including stable and long-term stable
distributions) have versions of GNU make that no longer have the
jobserver bug"
Tested-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This code is ancient, and goes back to when we only had a single page
for the pipe buffers. The exact history is hidden in the mists of time
(ie "before git", and in fact predates the BK repository too).
At that long-ago point in time, it actually helped to try to merge big
back-and-forth pipe reads and writes, and not limit pipe reads to the
single pipe buffer in length just because that was all we had at a time.
However, since then we've expanded the pipe buffers to multiple pages,
and this logic really doesn't seem to make sense. And a lot of it is
somewhat questionable (ie "hmm, the user asked for a non-blocking read,
but we see that there's a writer pending, so let's wait anyway to get
the extra data that the writer will have").
But more importantly, it makes the "go to sleep" logic much less
obvious, and considering the wakeup issues we've had, I want to make for
less of those kinds of things.
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Split pipe->ring_size into two numbers:
(1) pipe->ring_size - indicates the hard size of the pipe ring.
(2) pipe->max_usage - indicates the maximum number of pipe ring slots that
userspace orchestrated events can fill.
This allows for a pipe that is both writable by the general kernel
notification facility and by userspace, allowing plenty of ring space for
notifications to be added whilst preventing userspace from being able to
pin too much unswappable kernel space.
Signed-off-by: David Howells <dhowells@redhat.com>
Convert pipes to use head and tail pointers for the buffer ring rather than
pointer and length as the latter requires two atomic ops to update (or a
combined op) whereas the former only requires one.
(1) The head pointer is the point at which production occurs and points to
the slot in which the next buffer will be placed. This is equivalent
to pipe->curbuf + pipe->nrbufs.
The head pointer belongs to the write-side.
(2) The tail pointer is the point at which consumption occurs. It points
to the next slot to be consumed. This is equivalent to pipe->curbuf.
The tail pointer belongs to the read-side.
(3) head and tail are allowed to run to UINT_MAX and wrap naturally. They
are only masked off when the array is being accessed, e.g.:
pipe->bufs[head & mask]
This means that it is not necessary to have a dead slot in the ring as
head == tail isn't ambiguous.
(4) The ring is empty if "head == tail".
A helper, pipe_empty(), is provided for this.
(5) The occupancy of the ring is "head - tail".
A helper, pipe_occupancy(), is provided for this.
(6) The number of free slots in the ring is "pipe->ring_size - occupancy".
A helper, pipe_space_for_user() is provided to indicate how many slots
userspace may use.
(7) The ring is full if "head - tail >= pipe->ring_size".
A helper, pipe_full(), is provided for this.
Signed-off-by: David Howells <dhowells@redhat.com>
- Use "nosteal" for ring buffer splice pages
- Memory leak fix in error path of trace_pid_write()
- Fix preempt_enable_no_resched() (use preempt_enable()) in ring buffer code
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Merge tag 'trace-v5.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt:
"Three tracing fixes:
- Use "nosteal" for ring buffer splice pages
- Memory leak fix in error path of trace_pid_write()
- Fix preempt_enable_no_resched() (use preempt_enable()) in ring
buffer code"
* tag 'trace-v5.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
trace: Fix preempt_enable_no_resched() abuse
tracing: Fix a memory leak by early error exit in trace_pid_write()
tracing: Fix buffer_ref pipe ops
This fixes multiple issues in buffer_pipe_buf_ops:
- The ->steal() handler must not return zero unless the pipe buffer has
the only reference to the page. But generic_pipe_buf_steal() assumes
that every reference to the pipe is tracked by the page's refcount,
which isn't true for these buffers - buffer_pipe_buf_get(), which
duplicates a buffer, doesn't touch the page's refcount.
Fix it by using generic_pipe_buf_nosteal(), which refuses every
attempted theft. It should be easy to actually support ->steal, but the
only current users of pipe_buf_steal() are the virtio console and FUSE,
and they also only use it as an optimization. So it's probably not worth
the effort.
- The ->get() and ->release() handlers can be invoked concurrently on pipe
buffers backed by the same struct buffer_ref. Make them safe against
concurrency by using refcount_t.
- The pointers stored in ->private were only zeroed out when the last
reference to the buffer_ref was dropped. As far as I know, this
shouldn't be necessary anyway, but if we do it, let's always do it.
Link: http://lkml.kernel.org/r/20190404215925.253531-1-jannh@google.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Fixes: 73a757e631 ("ring-buffer: Return reader page back into existing ring buffer")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Merge page ref overflow branch.
Jann Horn reported that he can overflow the page ref count with
sufficient memory (and a filesystem that is intentionally extremely
slow).
Admittedly it's not exactly easy. To have more than four billion
references to a page requires a minimum of 32GB of kernel memory just
for the pointers to the pages, much less any metadata to keep track of
those pointers. Jann needed a total of 140GB of memory and a specially
crafted filesystem that leaves all reads pending (in order to not ever
free the page references and just keep adding more).
Still, we have a fairly straightforward way to limit the two obvious
user-controllable sources of page references: direct-IO like page
references gotten through get_user_pages(), and the splice pipe page
duplication. So let's just do that.
* branch page-refs:
fs: prevent page refcount overflow in pipe_buf_get
mm: prevent get_user_pages() from overflowing page refcount
mm: add 'try_get_page()' helper function
mm: make page ref count overflow check tighter and more explicit
Change pipe_buf_get() to return a bool indicating whether it succeeded
in raising the refcount of the page (if the thing in the pipe is a page).
This removes another mechanism for overflowing the page refcount. All
callers converted to handle a failure.
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Al Viro pointed out that since there is only one pipe buffer type to which
new data can be appended, it isn't necessary to have a ->can_merge field in
struct pipe_buf_operations, we can just check for a magic type.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Before this patch, it was possible for two pipes to affect each other after
data had been transferred between them with tee():
============
$ cat tee_test.c
int main(void) {
int pipe_a[2];
if (pipe(pipe_a)) err(1, "pipe");
int pipe_b[2];
if (pipe(pipe_b)) err(1, "pipe");
if (write(pipe_a[1], "abcd", 4) != 4) err(1, "write");
if (tee(pipe_a[0], pipe_b[1], 2, 0) != 2) err(1, "tee");
if (write(pipe_b[1], "xx", 2) != 2) err(1, "write");
char buf[5];
if (read(pipe_a[0], buf, 4) != 4) err(1, "read");
buf[4] = 0;
printf("got back: '%s'\n", buf);
}
$ gcc -o tee_test tee_test.c
$ ./tee_test
got back: 'abxx'
$
============
As suggested by Al Viro, fix it by creating a separate type for
non-mergeable pipe buffers, then changing the types of buffers in
splice_pipe_to_pipe() and link_pipe().
Cc: <stable@vger.kernel.org>
Fixes: 7c77f0b3f9 ("splice: implement pipe to pipe splicing")
Fixes: 70524490ee ("[PATCH] splice: add support for sys_tee()")
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
A pipe's size is represented as an 'unsigned int'. As expected, writing a
value greater than UINT_MAX to /proc/sys/fs/pipe-max-size fails with
EINVAL. However, the F_SETPIPE_SZ fcntl silently truncates such values to
32 bits, rather than failing with EINVAL as expected. (It *does* fail
with EINVAL for values above (1 << 31) but <= UINT_MAX.)
Fix this by moving the check against UINT_MAX into round_pipe_size() which
is called in both cases.
Link: http://lkml.kernel.org/r/20180111052902.14409-6-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
pipe_proc_fn() is no longer needed, as it only calls through to
proc_dopipe_max_size(). Just put proc_dopipe_max_size() in the ctl_table
entry directly, and remove the unneeded EXPORT_SYMBOL() and the ENOSYS
stub for it.
(The reason the ENOSYS stub isn't needed is that the pipe-max-size
ctl_table entry is located directly in 'kern_table' rather than being
registered separately. Therefore, the entry is already only defined when
the kernel is built with sysctl support.)
Link: http://lkml.kernel.org/r/20180111052902.14409-3-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "pipe: buffer limits fixes and cleanups", v2.
This series simplifies the sysctl handler for pipe-max-size and fixes
another set of bugs related to the pipe buffer limits:
- The root user wasn't allowed to exceed the limits when creating new
pipes.
- There was an off-by-one error when checking the limits, so a limit of
N was actually treated as N - 1.
- F_SETPIPE_SZ accepted values over UINT_MAX.
- Reading the pipe buffer limits could be racy.
This patch (of 7):
Before validating the given value against pipe_min_size,
do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
value up to pipe_min_size. Therefore, the second check against
pipe_min_size is redundant. Remove it.
Link: http://lkml.kernel.org/r/20180111052902.14409-2-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
pipe_max_size is assigned directly via procfs sysctl:
static struct ctl_table fs_table[] = {
...
{
.procname = "pipe-max-size",
.data = &pipe_max_size,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &pipe_proc_fn,
.extra1 = &pipe_min_size,
},
...
int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
size_t *lenp, loff_t *ppos)
{
...
ret = proc_dointvec_minmax(table, write, buf, lenp, ppos)
...
and then later rounded in-place a few statements later:
...
pipe_max_size = round_pipe_size(pipe_max_size);
...
This leaves a window of time between initial assignment and rounding
that may be visible to other threads. (For example, one thread sets a
non-rounded value to pipe_max_size while another reads its value.)
Similar reads of pipe_max_size are potentially racy:
pipe.c :: alloc_pipe_info()
pipe.c :: pipe_set_size()
Add a new proc_dopipe_max_size() that consolidates reading the new value
from the user buffer, verifying bounds, and calling round_pipe_size()
with a single assignment to pipe_max_size.
Link: http://lkml.kernel.org/r/1507658689-11669-4-git-send-email-joe.lawrence@redhat.com
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
On no-so-small systems, it is possible for a single process to cause an
OOM condition by filling large pipes with data that are never read. A
typical process filling 4000 pipes with 1 MB of data will use 4 GB of
memory. On small systems it may be tricky to set the pipe max size to
prevent this from happening.
This patch makes it possible to enforce a per-user soft limit above
which new pipes will be limited to a single page, effectively limiting
them to 4 kB each, as well as a hard limit above which no new pipes may
be created for this user. This has the effect of protecting the system
against memory abuse without hurting other users, and still allowing
pipes to work correctly though with less data at once.
The limit are controlled by two new sysctls : pipe-user-pages-soft, and
pipe-user-pages-hard. Both may be disabled by setting them to zero. The
default soft limit allows the default number of FDs per process (1024)
to create pipes of the default size (64kB), thus reaching a limit of 64MB
before starting to create only smaller pipes. With 256 processes limited
to 1024 FDs each, this results in 1024*64kB + (256*1024 - 1024) * 4kB =
1084 MB of memory allocated for a user. The hard limit is disabled by
default to avoid breaking existing applications that make intensive use
of pipes (eg: for splicing).
Reported-by: socketpair@gmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Mitigates: CVE-2013-4312 (Linux 2.0+)
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull vfs updates from Al Viro:
"The first vfs pile, with deep apologies for being very late in this
window.
Assorted cleanups and fixes, plus a large preparatory part of iov_iter
work. There's a lot more of that, but it'll probably go into the next
merge window - it *does* shape up nicely, removes a lot of
boilerplate, gets rid of locking inconsistencie between aio_write and
splice_write and I hope to get Kent's direct-io rewrite merged into
the same queue, but some of the stuff after this point is having
(mostly trivial) conflicts with the things already merged into
mainline and with some I want more testing.
This one passes LTP and xfstests without regressions, in addition to
usual beating. BTW, readahead02 in ltp syscalls testsuite has started
giving failures since "mm/readahead.c: fix readahead failure for
memoryless NUMA nodes and limit readahead pages" - might be a false
positive, might be a real regression..."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
missing bits of "splice: fix racy pipe->buffers uses"
cifs: fix the race in cifs_writev()
ceph_sync_{,direct_}write: fix an oops on ceph_osdc_new_request() failure
kill generic_file_buffered_write()
ocfs2_file_aio_write(): switch to generic_perform_write()
ceph_aio_write(): switch to generic_perform_write()
xfs_file_buffered_aio_write(): switch to generic_perform_write()
export generic_perform_write(), start getting rid of generic_file_buffer_write()
generic_file_direct_write(): get rid of ppos argument
btrfs_file_aio_write(): get rid of ppos
kill the 5th argument of generic_file_buffered_write()
kill the 4th argument of __generic_file_aio_write()
lustre: don't open-code kernel_recvmsg()
ocfs2: don't open-code kernel_recvmsg()
drbd: don't open-code kernel_recvmsg()
constify blk_rq_map_user_iov() and friends
lustre: switch to kernel_sendmsg()
ocfs2: don't open-code kernel_sendmsg()
take iov_iter stuff to mm/iov_iter.c
process_vm_access: tidy up a bit
...
This patch fix spelling typo in Documentation/DocBook.
It is because .html and .xml files are generated by make htmldocs,
I have to fix a typo within the source files.
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Having this struct in module memory could Oops when if the module is
unloaded while the buffer still persists in a pipe.
Since sock_pipe_buf_ops is essentially the same as fuse_dev_pipe_buf_steal
merge them into nosteal_pipe_buf_ops (this is the same as
default_pipe_buf_ops except stealing the page from the buffer is not
allowed).
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
it's used only as a flag to distinguish normal pipes/FIFOs from the
internal per-task one used by file-to-file splice. And pipe->files
would work just as well for that purpose...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* new field - pipe->files; number of struct file over that pipe (all
sharing the same inode, of course); protected by inode->i_lock.
* pipe_release() decrements pipe->files, clears inode->i_pipe when
if the counter has reached 0 (all under ->i_lock) and, in that case,
frees pipe after having done pipe_unlock()
* fifo_open() starts with grabbing ->i_lock, and either bumps pipe->files
if ->i_pipe was non-NULL or allocates a new pipe (dropping and regaining
->i_lock) and rechecks ->i_pipe; if it's still NULL, inserts new pipe
there, otherwise bumps ->i_pipe->files and frees the one we'd allocated.
At that point we know that ->i_pipe is non-NULL and won't go away, so
we can do pipe_lock() on it and proceed as we used to. If we end up
failing, decrement pipe->files and if it reaches 0 clear ->i_pipe and
free the sucker after pipe_unlock().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull second vfs pile from Al Viro:
"The stuff in there: fsfreeze deadlock fixes by Jan (essentially, the
deadlock reproduced by xfstests 068), symlink and hardlink restriction
patches, plus assorted cleanups and fixes.
Note that another fsfreeze deadlock (emergency thaw one) is *not*
dealt with - the series by Fernando conflicts a lot with Jan's, breaks
userland ABI (FIFREEZE semantics gets changed) and trades the deadlock
for massive vfsmount leak; this is going to be handled next cycle.
There probably will be another pull request, but that stuff won't be
in it."
Fix up trivial conflicts due to unrelated changes next to each other in
drivers/{staging/gdm72xx/usb_boot.c, usb/gadget/storage_common.c}
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (54 commits)
delousing target_core_file a bit
Documentation: Correct s_umount state for freeze_fs/unfreeze_fs
fs: Remove old freezing mechanism
ext2: Implement freezing
btrfs: Convert to new freezing mechanism
nilfs2: Convert to new freezing mechanism
ntfs: Convert to new freezing mechanism
fuse: Convert to new freezing mechanism
gfs2: Convert to new freezing mechanism
ocfs2: Convert to new freezing mechanism
xfs: Convert to new freezing code
ext4: Convert to new freezing mechanism
fs: Protect write paths by sb_start_write - sb_end_write
fs: Skip atime update on frozen filesystem
fs: Add freezing handling to mnt_want_write() / mnt_drop_write()
fs: Improve filesystem freezing handling
switch the protection of percpu_counter list to spinlock
nfsd: Push mnt_want_write() outside of i_mutex
btrfs: Push mnt_want_write() outside of i_mutex
fat: Push mnt_want_write() outside of i_mutex
...
The actual internal pipe implementation is already really about
individual packets (called "pipe buffers"), and this simply exposes that
as a special packetized mode.
When we are in the packetized mode (marked by O_DIRECT as suggested by
Alan Cox), a write() on a pipe will not merge the new data with previous
writes, so each write will get a pipe buffer of its own. The pipe
buffer is then marked with the PIPE_BUF_FLAG_PACKET flag, which in turn
will tell the reader side to break the read at that boundary (and throw
away any partial packet contents that do not fit in the read buffer).
End result: as long as you do writes less than PIPE_BUF in size (so that
the pipe doesn't have to split them up), you can now treat the pipe as a
packet interface, where each read() system call will read one packet at
a time. You can just use a sufficiently big read buffer (PIPE_BUF is
sufficient, since bigger than that doesn't guarantee atomicity anyway),
and the return value of the read() will naturally give you the size of
the packet.
NOTE! We do not support zero-sized packets, and zero-sized reads and
writes to a pipe continue to be no-ops. Also note that big packets will
currently be split at write time, but that the size at which that
happens is not really specified (except that it's bigger than PIPE_BUF).
Currently that limit is the system page size, but we might want to
explicitly support bigger packets some day.
The main user for this is going to be the autofs packet interface,
allowing us to stop having to care so deeply about exact packet sizes
(which have had bugs with 32/64-bit compatibility modes). But user
space can create packetized pipes with "pipe2(fd, O_DIRECT)", which will
fail with an EINVAL on kernels that do not support this interface.
Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Miller <davem@davemloft.net>
Cc: Ian Kent <raven@themaw.net>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: stable@kernel.org # needed for systemd/autofs interaction fix
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Move open-coded filesystem magic numbers into magic.h
- Rearrange magic.h so that the filesystem-related constants are grouped
together.
Signed-off-by: Muthukumar R <muthur@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix kernel-doc notation warnings in pipe_fs_i.h:
Warning(include/linux/pipe_fs_i.h:58): No description found for parameter 'buffers'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This avoids some include-file hell, and the function isn't really
important enough to be inlined anyway.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
And in particular, use it in 'pipe_fcntl()'.
The other pipe functions do not need to use the 'careful' version, since
they are only ever called for things that are already known to be pipes.
The normal read/write/ioctl functions are called through the file
operations structures, so if a file isn't a pipe, they'd never get
called. But pipe_fcntl() is special, and called directly from the
generic fcntl code, and needs to use the same careful function that the
splice code is using.
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This changes the interface to be based on bytes instead. The API
matches that of F_SETPIPE_SZ in that it rounds up the passed in
size so that the resulting page array is a power-of-2 in size.
The proc file is renamed to /proc/sys/fs/pipe-max-size to
reflect this change.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
We need at least two to guarantee proper POSIX behaviour, so
never allow a smaller limit than that.
Also expose a /proc/sys/fs/pipe-max-pages sysctl file that allows
root to define a sane upper limit. Make it default to 16 times the
default size, which is 16 pages.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This patch adds F_GETPIPE_SZ and F_SETPIPE_SZ fcntl() actions for
growing and shrinking the size of a pipe and adjusts pipe.c and splice.c
(and relay and network splice) usage to work with these larger (or smaller)
pipes.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
If f_op->splice_read() is not implemented, fall back to a plain read.
Use vfs_readv() to read into previously allocated pages.
This will allow splice and functions using splice, such as the loop
device, to work on all filesystems. This includes "direct_io" files
in fuse which bypass the page cache.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
There are lots of sequences like this, especially in splice code:
if (pipe->inode)
mutex_lock(&pipe->inode->i_mutex);
/* do something */
if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex);
so introduce helpers which do the conditional locking and unlocking.
Also replace the inode_double_lock() call with a pipe_double_lock()
helper to avoid spreading the use of this functionality beyond the
pipe code.
This patch is just a cleanup, and should cause no behavioral changes.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
As per Andrew Mortons request, here's a set of documentation for
the generic pipe_buf_operations hooks, the pipe, and pipe_buffer
structures.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
The name 'pin' was badly chosen, it doesn't pin a pipe buffer
in the most commonly used sense in the kernel. So change the
name to 'confirm', after debating this issue with Hugh
Dickins a bit.
A good return from ->confirm() means that the buffer is really
there, and that the contents are good.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
relay needs this for proper consumption handling, and the network
receive support needs it as well to lookup the sk_buff on pipe
release.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
We need to move even more stuff into the header so that folks can use
the splice_to_pipe() implementation instead of open-coding a lot of
pipe knowledge (see relay implementation), so move to our own header
file finally.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
