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fs/file.c: remove sanity_check and add likely/unlikely in alloc_fd()

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alloc_fd() has a sanity check inside to make sure the struct file mapping to the
allocated fd is NULL. Remove this sanity check since it can be assured by
exisitng zero initilization and NULL set when recycling fd. Meanwhile, add
likely/unlikely and expand_file() call avoidance to reduce the work under
file_lock.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Yu Ma <yu.ma@intel.com>
Link: https://lore.kernel.org/r/20240717145018.3972922-2-yu.ma@intel.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Yu Ma 2024-07-17 10:50:16 -04:00 committed by Al Viro
parent cab0515211
commit 52732bb9ab
1 changed files with 14 additions and 19 deletions
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33
fs/file.c
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@ -496,7 +496,7 @@ repeat:
if (fd < files->next_fd)
fd = files->next_fd;
if (fd < fdt->max_fds)
if (likely(fd < fdt->max_fds))
fd = find_next_fd(fdt, fd);
/*
@ -504,19 +504,21 @@ repeat:
* will limit the total number of files that can be opened.
*/
error = -EMFILE;
if (fd >= end)
if (unlikely(fd >= end))
goto out;
error = expand_files(files, fd);
if (error < 0)
goto out;
if (unlikely(fd >= fdt->max_fds)) {
error = expand_files(files, fd);
if (error < 0)
goto out;
/*
* If we needed to expand the fs array we
* might have blocked - try again.
*/
if (error)
goto repeat;
/*
* If we needed to expand the fs array we
* might have blocked - try again.
*/
if (error)
goto repeat;
}
if (start <= files->next_fd)
files->next_fd = fd + 1;
@ -527,13 +529,6 @@ repeat:
else
__clear_close_on_exec(fd, fdt);
error = fd;
#if 1
/* Sanity check */
if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
rcu_assign_pointer(fdt->fd[fd], NULL);
}
#endif
out:
spin_unlock(&files->file_lock);
@ -599,7 +594,7 @@ void fd_install(unsigned int fd, struct file *file)
rcu_read_unlock_sched();
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
BUG_ON(fdt->fd[fd] != NULL);
WARN_ON(fdt->fd[fd] != NULL);
rcu_assign_pointer(fdt->fd[fd], file);
spin_unlock(&files->file_lock);
return;