Now that we shrank struct file by 24 bytes we still have a 4 byte hole.
Move f_version into the union and f_iocb_flags out of the union to fill
that hole and shrink struct file by another 4 bytes. This brings struct
file to 200 bytes down from 232 bytes.
I've tried to audit all codepaths that use f_version and none of them
rely on it in file->f_op->release() and never have since commit
1da177e4c3f4 ("Linux-2.6.12-rc2").
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
struct file {
union {
struct callback_head f_task_work; /* 0 16 */
struct llist_node f_llist; /* 0 8 */
u64 f_version; /* 0 8 */
}; /* 0 16 */
spinlock_t f_lock; /* 16 4 */
fmode_t f_mode; /* 20 4 */
atomic_long_t f_count; /* 24 8 */
struct mutex f_pos_lock; /* 32 32 */
/* --- cacheline 1 boundary (64 bytes) --- */
loff_t f_pos; /* 64 8 */
unsigned int f_flags; /* 72 4 */
unsigned int f_iocb_flags; /* 76 4 */
struct fown_struct * f_owner; /* 80 8 */
const struct cred * f_cred; /* 88 8 */
struct file_ra_state f_ra; /* 96 32 */
/* --- cacheline 2 boundary (128 bytes) --- */
struct path f_path; /* 128 16 */
struct inode * f_inode; /* 144 8 */
const struct file_operations * f_op; /* 152 8 */
void * f_security; /* 160 8 */
void * private_data; /* 168 8 */
struct hlist_head * f_ep; /* 176 8 */
struct address_space * f_mapping; /* 184 8 */
/* --- cacheline 3 boundary (192 bytes) --- */
errseq_t f_wb_err; /* 192 4 */
errseq_t f_sb_err; /* 196 4 */
/* size: 200, cachelines: 4, members: 20 */
/* last cacheline: 8 bytes */
};
---
include/linux/fs.h | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7eb4f706d59f..7a2994405e8e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -998,9 +998,8 @@ struct file {
struct callback_head f_task_work;
/* fput() must use workqueue (most kernel threads). */
struct llist_node f_llist;
- unsigned int f_iocb_flags;
+ u64 f_version;
};
-
/*
* Protects f_ep, f_flags.
* Must not be taken from IRQ context.
@@ -1011,6 +1010,7 @@ struct file {
struct mutex f_pos_lock;
loff_t f_pos;
unsigned int f_flags;
+ unsigned int f_iocb_flags;
struct fown_struct *f_owner;
const struct cred *f_cred;
struct file_ra_state f_ra;
@@ -1018,7 +1018,6 @@ struct file {
struct inode *f_inode; /* cached value */
const struct file_operations *f_op;
- u64 f_version;
#ifdef CONFIG_SECURITY
void *f_security;
#endif
--
2.43.0
