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  1. 01 11月, 2016 1 次提交
  3. 28 10月, 2016 1 次提交
    • C
      block: better op and flags encoding · ef295ecf
      由 Christoph Hellwig 提交于 
      Now that we don't need the common flags to overflow outside the range
of a 32-bit type we can encode them the same way for both the bio and
request fields.  This in addition allows us to place the operation
first (and make some room for more ops while we're at it) and to
stop having to shift around the operation values.

In addition this allows passing around only one value in the block layer
instead of two (and eventuall also in the file systems, but we can do
that later) and thus clean up a lot of code.

Last but not least this allows decreasing the size of the cmd_flags
field in struct request to 32-bits.  Various functions passing this
value could also be updated, but I'd like to avoid the churn for now.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>
      ef295ecf
  5. 18 10月, 2016 1 次提交
  7. 15 10月, 2016 6 次提交
  9. 14 10月, 2016 12 次提交
  11. 13 10月, 2016 11 次提交
  13. 12 10月, 2016 8 次提交
    • M
      fs: use mapping_set_error instead of opencoded set_bit · 5114a97a
      由 Michal Hocko 提交于 
      The mapping_set_error() helper sets the correct AS_ flag for the mapping
so there is no reason to open code it.  Use the helper directly.

[akpm@linux-foundation.org: be honest about conversion from -ENXIO to -EIO]
Link: http://lkml.kernel.org/r/20160912111608.2588-2-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5114a97a
    • M
      treewide: remove redundant #include <linux/kconfig.h> · 97139d4a
      由 Masahiro Yamada 提交于 
      Kernel source files need not include <linux/kconfig.h> explicitly
because the top Makefile forces to include it with:

  -include $(srctree)/include/linux/kconfig.h

This commit removes explicit includes except the following:

  * arch/s390/include/asm/facilities_src.h
  * tools/testing/radix-tree/linux/kernel.h

These two are used for host programs.

Link: http://lkml.kernel.org/r/1473656164-11929-1-git-send-email-yamada.masahiro@socionext.comSigned-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      97139d4a
    • M
      pipe: cap initial pipe capacity according to pipe-max-size limit · 086e774a
      由 Michael Kerrisk (man-pages) 提交于 
      This is a patch that provides behavior that is more consistent, and
probably less surprising to users. I consider the change optional, and
welcome opinions about whether it should be applied.

By default, pipes are created with a capacity of 64 kiB.  However,
/proc/sys/fs/pipe-max-size may be set smaller than this value.  In this
scenario, an unprivileged user could thus create a pipe whose initial
capacity exceeds the limit. Therefore, it seems logical to cap the
initial pipe capacity according to the value of pipe-max-size.

The test program shown earlier in this patch series can be used to
demonstrate the effect of the change brought about with this patch:

    # cat /proc/sys/fs/pipe-max-size
    1048576
    # sudo -u mtk ./test_F_SETPIPE_SZ 1
    Initial pipe capacity: 65536
    # echo 10000 > /proc/sys/fs/pipe-max-size
    # cat /proc/sys/fs/pipe-max-size
    16384
    # sudo -u mtk ./test_F_SETPIPE_SZ 1
    Initial pipe capacity: 16384
    # ./test_F_SETPIPE_SZ 1
    Initial pipe capacity: 65536

The last two executions of 'test_F_SETPIPE_SZ' show that pipe-max-size
caps the initial allocation for a new pipe for unprivileged users, but
not for privileged users.

Link: http://lkml.kernel.org/r/31dc7064-2a17-9c5b-1df1-4e3012ee992c@gmail.comSigned-off-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: NVegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      086e774a
    • M
      pipe: make account_pipe_buffers() return a value, and use it · 9c87bcf0
      由 Michael Kerrisk (man-pages) 提交于 
      This is an optional patch, to provide a small performance
improvement.  Alter account_pipe_buffers() so that it returns the
new value in user->pipe_bufs. This means that we can refactor
too_many_pipe_buffers_soft() and too_many_pipe_buffers_hard() to
avoid the costs of repeated use of atomic_long_read() to get the
value user->pipe_bufs.

Link: http://lkml.kernel.org/r/93e5f193-1e5e-3e1f-3a20-eae79b7e1310@gmail.comSigned-off-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: NVegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9c87bcf0
    • M
      pipe: fix limit checking in alloc_pipe_info() · a005ca0e
      由 Michael Kerrisk (man-pages) 提交于 
      The limit checking in alloc_pipe_info() (used by pipe(2) and when
opening a FIFO) has the following problems:

(1) When checking capacity required for the new pipe, the checks against
    the limit in /proc/sys/fs/pipe-user-pages-{soft,hard} are made
    against existing consumption, and exclude the memory required for
    the new pipe capacity. As a consequence: (1) the memory allocation
    throttling provided by the soft limit does not kick in quite as
    early as it should, and (2) the user can overrun the hard limit.

(2) As currently implemented, accounting and checking against the limits
    is done as follows:

    (a) Test whether the user has exceeded the limit.
    (b) Make new pipe buffer allocation.
    (c) Account new allocation against the limits.

    This is racey. Multiple processes may pass point (a) simultaneously,
    and then allocate pipe buffers that are accounted for only in step
    (c).  The race means that the user's pipe buffer allocation could be
    pushed over the limit (by an arbitrary amount, depending on how
    unlucky we were in the race). [Thanks to Vegard Nossum for spotting
    this point, which I had missed.]

This patch addresses the above problems as follows:

* Alter the checks against limits to include the memory required for the
  new pipe.
* Re-order the accounting step so that it precedes the buffer allocation.
  If the accounting step determines that a limit has been reached, revert
  the accounting and cause the operation to fail.

Link: http://lkml.kernel.org/r/8ff3e9f9-23f6-510c-644f-8e70cd1c0bd9@gmail.comSigned-off-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: NVegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a005ca0e
    • M
      pipe: simplify logic in alloc_pipe_info() · 09b4d199
      由 Michael Kerrisk (man-pages) 提交于 
      Replace an 'if' block that covers most of the code in this function
with a 'goto'. This makes the code a little simpler to read, and also
simplifies the next patch (fix limit checking in alloc_pipe_info())

Link: http://lkml.kernel.org/r/aef030c1-0257-98a9-4988-186efa48530c@gmail.comSigned-off-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: NVegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      09b4d199
    • M
      pipe: fix limit checking in pipe_set_size() · b0b91d18
      由 Michael Kerrisk (man-pages) 提交于 
      The limit checking in pipe_set_size() (used by fcntl(F_SETPIPE_SZ))
has the following problems:

(1) When increasing the pipe capacity, the checks against the limits in
    /proc/sys/fs/pipe-user-pages-{soft,hard} are made against existing
    consumption, and exclude the memory required for the increased pipe
    capacity. The new increase in pipe capacity can then push the total
    memory used by the user for pipes (possibly far) over a limit. This
    can also trigger the problem described next.

(2) The limit checks are performed even when the new pipe capacity is
    less than the existing pipe capacity. This can lead to problems if a
    user sets a large pipe capacity, and then the limits are lowered,
    with the result that the user will no longer be able to decrease the
    pipe capacity.

(3) As currently implemented, accounting and checking against the
    limits is done as follows:

    (a) Test whether the user has exceeded the limit.
    (b) Make new pipe buffer allocation.
    (c) Account new allocation against the limits.

    This is racey. Multiple processes may pass point (a)
    simultaneously, and then allocate pipe buffers that are accounted
    for only in step (c).  The race means that the user's pipe buffer
    allocation could be pushed over the limit (by an arbitrary amount,
    depending on how unlucky we were in the race). [Thanks to Vegard
    Nossum for spotting this point, which I had missed.]

This patch addresses the above problems as follows:

* Perform checks against the limits only when increasing a pipe's
  capacity; an unprivileged user can always decrease a pipe's capacity.
* Alter the checks against limits to include the memory required for
  the new pipe capacity.
* Re-order the accounting step so that it precedes the buffer
  allocation. If the accounting step determines that a limit has
  been reached, revert the accounting and cause the operation to fail.

The program below can be used to demonstrate problems 1 and 2, and the
effect of the fix. The program takes one or more command-line arguments.
The first argument specifies the number of pipes that the program should
create. The remaining arguments are, alternately, pipe capacities that
should be set using fcntl(F_SETPIPE_SZ), and sleep intervals (in
seconds) between the fcntl() operations. (The sleep intervals allow the
possibility to change the limits between fcntl() operations.)

Problem 1
=========

Using the test program on an unpatched kernel, we first set some
limits:

    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard    # 40.96 MB

Then show that we can set a pipe with capacity (100MB) that is
over the hard limit

    # sudo -u mtk ./test_F_SETPIPE_SZ 1 100000000
    Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 100000000 bytes
            F_SETPIPE_SZ returned 134217728

Now set the capacity to 100MB twice. The second call fails (which is
probably surprising to most users, since it seems like a no-op):

    # sudo -u mtk ./test_F_SETPIPE_SZ 1 100000000 0 100000000
    Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 100000000 bytes
            F_SETPIPE_SZ returned 134217728
        Loop 2: set pipe capacity to 100000000 bytes
            Loop 2, pipe 0: F_SETPIPE_SZ failed: fcntl: Operation not permitted

With a patched kernel, setting a capacity over the limit fails at the
first attempt:

    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard
    # sudo -u mtk ./test_F_SETPIPE_SZ 1 100000000
    Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 100000000 bytes
            Loop 1, pipe 0: F_SETPIPE_SZ failed: fcntl: Operation not permitted

There is a small chance that the change to fix this problem could
break user-space, since there are cases where fcntl(F_SETPIPE_SZ)
calls that previously succeeded might fail. However, the chances are
small, since (a) the pipe-user-pages-{soft,hard} limits are new (in
4.5), and the default soft/hard limits are high/unlimited.  Therefore,
it seems warranted to make these limits operate more precisely (and
behave more like what users probably expect).

Problem 2
=========

Running the test program on an unpatched kernel, we first set some limits:

    # getconf PAGESIZE
    4096
    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard    # 40.96 MB

Now perform two fcntl(F_SETPIPE_SZ) operations on a single pipe,
first setting a pipe capacity (10MB), sleeping for a few seconds,
during which time the hard limit is lowered, and then set pipe
capacity to a smaller amount (5MB):

    # sudo -u mtk ./test_F_SETPIPE_SZ 1 10000000 15 5000000 &
    [1] 748
    # Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 10000000 bytes
            F_SETPIPE_SZ returned 16777216
            Sleeping 15 seconds

    # echo 1000 > /proc/sys/fs/pipe-user-pages-hard      # 4.096 MB
    #     Loop 2: set pipe capacity to 5000000 bytes
            Loop 2, pipe 0: F_SETPIPE_SZ failed: fcntl: Operation not permitted

In this case, the user should be able to lower the limit.

With a kernel that has the patch below, the second fcntl()
succeeds:

    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard
    # sudo -u mtk ./test_F_SETPIPE_SZ 1 10000000 15 5000000 &
    [1] 3215
    # Initial pipe capacity: 65536
    #     Loop 1: set pipe capacity to 10000000 bytes
            F_SETPIPE_SZ returned 16777216
            Sleeping 15 seconds

    # echo 1000 > /proc/sys/fs/pipe-user-pages-hard

    #     Loop 2: set pipe capacity to 5000000 bytes
            F_SETPIPE_SZ returned 8388608

8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---

/* test_F_SETPIPE_SZ.c

   (C) 2016, Michael Kerrisk; licensed under GNU GPL version 2 or later

   Test operation of fcntl(F_SETPIPE_SZ) for setting pipe capacity
   and interactions with limits defined by /proc/sys/fs/pipe-* files.
*/

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

int
main(int argc, char *argv[])
{
    int (*pfd)[2];
    int npipes;
    int pcap, rcap;
    int j, p, s, stime, loop;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s num-pipes "
                "[pipe-capacity sleep-time]...\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    npipes = atoi(argv[1]);

    pfd = calloc(npipes, sizeof (int [2]));
    if (pfd == NULL) {
        perror("calloc");
        exit(EXIT_FAILURE);
    }

    for (j = 0; j < npipes; j++) {
        if (pipe(pfd[j]) == -1) {
            fprintf(stderr, "Loop %d: pipe() failed: ", j);
            perror("pipe");
            exit(EXIT_FAILURE);
        }
    }

    printf("Initial pipe capacity: %d\n", fcntl(pfd[0][0], F_GETPIPE_SZ));

    for (j = 2; j < argc; j += 2 ) {
        loop = j / 2;
        pcap = atoi(argv[j]);
        printf("    Loop %d: set pipe capacity to %d bytes\n", loop, pcap);

        for (p = 0; p < npipes; p++) {
            s = fcntl(pfd[p][0], F_SETPIPE_SZ, pcap);
            if (s == -1) {
                fprintf(stderr, "        Loop %d, pipe %d: F_SETPIPE_SZ "
                        "failed: ", loop, p);
                perror("fcntl");
                exit(EXIT_FAILURE);
            }

            if (p == 0) {
                printf("        F_SETPIPE_SZ returned %d\n", s);
                rcap = s;
            } else {
                if (s != rcap) {
                    fprintf(stderr, "        Loop %d, pipe %d: F_SETPIPE_SZ "
                            "unexpected return: %d\n", loop, p, s);
                    exit(EXIT_FAILURE);
                }
            }

            stime = (j + 1 < argc) ? atoi(argv[j + 1]) : 0;
            if (stime > 0) {
                printf("        Sleeping %d seconds\n", stime);
                sleep(stime);
            }
        }
    }

    exit(EXIT_SUCCESS);
}

8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---

Patch history:

v2
   * Switch order of test in 'if' statement to avoid function call
      (to capability()) in normal path. [This is a fix to a preexisting
      wart in the code. Thanks to Willy Tarreau]
    * Perform (size > pipe_max_size) check before calling
      account_pipe_buffers().  [Thanks to Vegard Nossum]
      Quoting Vegard:

        The potential problem happens if the user passes a very large number
        which will overflow pipe->user->pipe_bufs.

        On 32-bit, sizeof(int) == sizeof(long), so if they pass arg = INT_MAX
        then round_pipe_size() returns INT_MAX. Although it's true that the
        accounting is done in terms of pages and not bytes, so you'd need on
        the order of (1 << 13) = 8192 processes hitting the limit at the same
        time in order to make it overflow, which seems a bit unlikely.

        (See https://lkml.org/lkml/2016/8/12/215 for another discussion on the
        limit checking)

Link: http://lkml.kernel.org/r/1e464945-536b-2420-798b-e77b9c7e8593@gmail.comSigned-off-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: NVegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b0b91d18
    • M
      pipe: refactor argument for account_pipe_buffers() · 3734a13b
      由 Michael Kerrisk (man-pages) 提交于 
      This is a preparatory patch for following work. account_pipe_buffers()
performs accounting in the 'user_struct'. There is no need to pass a
pointer to a 'pipe_inode_info' struct (which is then dereferenced to
obtain a pointer to the 'user' field). Instead, pass a pointer directly
to the 'user_struct'. This change is needed in preparation for a
subsequent patch that the fixes the limit checking in alloc_pipe_info()
(and the resulting code is a little more logical).

Link: http://lkml.kernel.org/r/7277bf8c-a6fc-4a7d-659c-f5b145c981ab@gmail.comSigned-off-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: NVegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3734a13b