From 78eeae60bb5a978eae4c3ce705c58189b762a24b Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Wed, 25 Sep 2024 17:49:56 -0700 Subject: [PATCH] Initialize session buffer size to value set by sysctl Currently in libfuse, the buffer size for a fuse session is capped at 1 MiB on a 4k page system. A recent patch upstream [1] was merged that allows the max number of pages per fuse request to be dynamically configurable through the /proc/sys interface (/proc/sys/fs/fuse/max_pages_limit). This commit adds support for this on the libfuse side to set the fuse session buffer to take into account the max pages limit set in /proc/sys/fs/fuse/max_pages_limit. If this sysctl does not exist (eg older kernels), it will default to old behavior (using FUSE_MAX_MAX_PAGES (256) as the max pages limit). This allows for things like bigger write buffers per request. [1] https://lore.kernel.org/linux-fsdevel/20240923171311.1561917-1-joannelkoong@gmail.com/T/#t --- lib/fuse_lowlevel.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c index 8bfeb01..824dbab 100644 --- a/lib/fuse_lowlevel.c +++ b/lib/fuse_lowlevel.c @@ -2907,6 +2907,29 @@ static void fuse_ll_pipe_destructor(void *data) fuse_ll_pipe_free(llp); } +static unsigned int get_max_pages(void) +{ + char buf[32]; + int res; + int fd; + + fd = open("/proc/sys/fs/fuse/max_pages_limit", O_RDONLY); + if (fd < 0) + return FUSE_MAX_MAX_PAGES; + + res = read(fd, buf, sizeof(buf) - 1); + + close(fd); + + if (res < 0) + return FUSE_MAX_MAX_PAGES; + + buf[res] = '\0'; + + res = strtol(buf, NULL, 10); + return res < 0 ? FUSE_MAX_MAX_PAGES : res; +} + int fuse_session_receive_buf(struct fuse_session *se, struct fuse_buf *buf) { return fuse_session_receive_buf_int(se, buf, NULL); @@ -3142,7 +3165,7 @@ struct fuse_session *_fuse_session_new_317(struct fuse_args *args, if (se->debug) fuse_log(FUSE_LOG_DEBUG, "FUSE library version: %s\n", PACKAGE_VERSION); - se->bufsize = FUSE_MAX_MAX_PAGES * getpagesize() + + se->bufsize = get_max_pages() * getpagesize() + FUSE_BUFFER_HEADER_SIZE; list_init_req(&se->list); -- 2.30.2