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fs: add f_pipe

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Only regular files with FMODE_ATOMIC_POS and directories need
f_pos_lock. Place a new f_pipe member in a union with f_pos_lock
that they can use and make them stop abusing f_version in follow-up
patches.

Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-18-6d3e4816aa7b@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-08-30 15:04:59 +02:00
parent 1146e5a69e
commit 5e9b50dea9
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GPG Key ID: 91C61BC06578DCA2
2 changed files with 14 additions and 1 deletions
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7
fs/file_table.c
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@ -156,6 +156,13 @@ static int init_file(struct file *f, int flags, const struct cred *cred)
}
spin_lock_init(&f->f_lock);
/*
* Note that f_pos_lock is only used for files raising
* FMODE_ATOMIC_POS and directories. Other files such as pipes
* don't need it and since f_pos_lock is in a union may reuse
* the space for other purposes. They are expected to initialize
* the respective member when opening the file.
*/
mutex_init(&f->f_pos_lock);
f->f_flags = flags;
f->f_mode = OPEN_FMODE(flags);

8
include/linux/fs.h
View File

@ -1001,6 +1001,7 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
* @f_cred: stashed credentials of creator/opener
* @f_path: path of the file
* @f_pos_lock: lock protecting file position
* @f_pipe: specific to pipes
* @f_pos: file position
* @f_version: file version
* @f_security: LSM security context of this file
@ -1026,7 +1027,12 @@ struct file {
const struct cred *f_cred;
/* --- cacheline 1 boundary (64 bytes) --- */
struct path f_path;
struct mutex f_pos_lock;
union {
/* regular files (with FMODE_ATOMIC_POS) and directories */
struct mutex f_pos_lock;
/* pipes */
u64 f_pipe;
};
loff_t f_pos;
u64 f_version;
/* --- cacheline 2 boundary (128 bytes) --- */