diff options
Diffstat (limited to 'fs/pipe.c')
-rw-r--r-- | fs/pipe.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 6534470a6c19..37a003b645ef 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -28,6 +28,21 @@ #include "internal.h" /* + * New pipe buffers will be restricted to this size while the user is exceeding + * their pipe buffer quota. The general pipe use case needs at least two + * buffers: one for data yet to be read, and one for new data. If this is less + * than two, then a write to a non-empty pipe may block even if the pipe is not + * full. This can occur with GNU make jobserver or similar uses of pipes as + * semaphores: multiple processes may be waiting to write tokens back to the + * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/. + * + * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their + * own risk, namely: pipe writes to non-full pipes may block until the pipe is + * emptied. + */ +#define PIPE_MIN_DEF_BUFFERS 2 + +/* * The max size that a non-root user is allowed to grow the pipe. Can * be set by root in /proc/sys/fs/pipe-max-size */ @@ -621,7 +636,7 @@ struct pipe_inode_info *alloc_pipe_info(void) if (!too_many_pipe_buffers_hard(user)) { if (too_many_pipe_buffers_soft(user)) - pipe_bufs = 1; + pipe_bufs = PIPE_MIN_DEF_BUFFERS; pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL); } |