[Devel] [PATCH RH8 2/3] ve/fs/files: Add fdtable_align() helper

[Andrey Zhadchenko]

From: Kirill Tkhai <ktkhai at virtuozzo.com>

Patchset description:
Shrink big fdtable on criu restore

This patchset allows to avoid memory overuse introduced by service fds on criu
restore.
The solution is simple: smartly check for closed fd number, and shrink fdtable
if this could be made. The checks are happen in is_pseudosuper mode, so we do
not affect performance on normal work mode.

The problem is we can't solve this for 100% case in userspace.
Kernel allows to fix that completely.

https://jira.sw.ru/browse/PSBM-78827

Eric Dumazet (1):
      ms/fs/file.c: don't acquire files->file_lock in fd_install()

Kirill Tkhai (3):
      files: Add new argument to expand_files()
      files: Add fdtable_align() helper
      files: Shrink big fdtable on close in is_pseudosuper mode

Mateusz Guzik (1):
      ms/vfs: grab the lock instead of blocking in __fd_install during resizing

============================================================
This patch description:

Move alignment functionality from expand_fdtable() to separate function.
This will be used in next patch.

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
Reviewed-by: Cyrill Gorcunov <gorcunov at openvz.org>

(cherry picked from 2437df57ec6e7194d431ea1c632f6e87a825dae9)
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
 fs/file.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index 866912f..4f68ef0f 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -82,11 +82,8 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt, bool shrink
 	copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
 }
 
-static struct fdtable * alloc_fdtable(unsigned int nr)
+static unsigned int fdtable_align(unsigned int nr)
 {
-	struct fdtable *fdt;
-	void *data;
-
 	/*
 	 * Figure out how many fds we actually want to support in this fdtable.
 	 * Allocation steps are keyed to the size of the fdarray, since it
@@ -108,6 +105,16 @@ static struct fdtable * alloc_fdtable(unsigned int nr)
 	if (unlikely(nr > sysctl_nr_open))
 		nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
 
+	return nr;
+}
+
+static struct fdtable * alloc_fdtable(unsigned int nr)
+{
+	struct fdtable *fdt;
+	void *data;
+
+	nr = fdtable_align(nr);
+
 	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
 	if (!fdt)
 		goto out;
-- 
1.8.3.1