diff options
Diffstat (limited to 'fs/file.c')
| -rw-r--r-- | fs/file.c | 281 |
1 files changed, 148 insertions, 133 deletions
diff --git a/fs/file.c b/fs/file.c index 36ff81c90edb..fb1011cf6b4a 100644 --- a/fs/file.c +++ b/fs/file.c @@ -20,10 +20,73 @@ #include <linux/spinlock.h> #include <linux/rcupdate.h> #include <linux/close_range.h> +#include <linux/file_ref.h> #include <net/sock.h> #include "internal.h" +/** + * __file_ref_put - Slowpath of file_ref_put() + * @ref: Pointer to the reference count + * @cnt: Current reference count + * + * Invoked when the reference count is outside of the valid zone. + * + * Return: + * True if this was the last reference with no future references + * possible. This signals the caller that it can safely schedule the + * object, which is protected by the reference counter, for + * deconstruction. + * + * False if there are still active references or the put() raced + * with a concurrent get()/put() pair. Caller is not allowed to + * deconstruct the protected object. + */ +bool __file_ref_put(file_ref_t *ref, unsigned long cnt) +{ + /* Did this drop the last reference? */ + if (likely(cnt == FILE_REF_NOREF)) { + /* + * Carefully try to set the reference count to FILE_REF_DEAD. + * + * This can fail if a concurrent get() operation has + * elevated it again or the corresponding put() even marked + * it dead already. Both are valid situations and do not + * require a retry. If this fails the caller is not + * allowed to deconstruct the object. + */ + if (!atomic_long_try_cmpxchg_release(&ref->refcnt, &cnt, FILE_REF_DEAD)) + return false; + + /* + * The caller can safely schedule the object for + * deconstruction. Provide acquire ordering. + */ + smp_acquire__after_ctrl_dep(); + return true; + } + + /* + * If the reference count was already in the dead zone, then this + * put() operation is imbalanced. Warn, put the reference count back to + * DEAD and tell the caller to not deconstruct the object. + */ + if (WARN_ONCE(cnt >= FILE_REF_RELEASED, "imbalanced put on file reference count")) { + atomic_long_set(&ref->refcnt, FILE_REF_DEAD); + return false; + } + + /* + * This is a put() operation on a saturated refcount. Restore the + * mean saturation value and tell the caller to not deconstruct the + * object. + */ + if (cnt > FILE_REF_MAXREF) + atomic_long_set(&ref->refcnt, FILE_REF_SATURATED); + return false; +} +EXPORT_SYMBOL_GPL(__file_ref_put); + unsigned int sysctl_nr_open __read_mostly = 1024*1024; unsigned int sysctl_nr_open_min = BITS_PER_LONG; /* our min() is unusable in constant expressions ;-/ */ @@ -89,18 +152,11 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) * 'unsigned long' in some places, but simply because that is how the Linux * kernel bitmaps are defined to work: they are not "bits in an array of bytes", * they are very much "bits in an array of unsigned long". - * - * The ALIGN(nr, BITS_PER_LONG) here is for clarity: since we just multiplied - * by that "1024/sizeof(ptr)" before, we already know there are sufficient - * clear low bits. Clang seems to realize that, gcc ends up being confused. - * - * On a 128-bit machine, the ALIGN() would actually matter. In the meantime, - * let's consider it documentation (and maybe a test-case for gcc to improve - * its code generation ;) */ -static struct fdtable * alloc_fdtable(unsigned int nr) +static struct fdtable *alloc_fdtable(unsigned int slots_wanted) { struct fdtable *fdt; + unsigned int nr; void *data; /* @@ -108,22 +164,32 @@ static struct fdtable * alloc_fdtable(unsigned int nr) * Allocation steps are keyed to the size of the fdarray, since it * grows far faster than any of the other dynamic data. We try to fit * the fdarray into comfortable page-tuned chunks: starting at 1024B - * and growing in powers of two from there on. + * and growing in powers of two from there on. Since we called only + * with slots_wanted > BITS_PER_LONG (embedded instance in files->fdtab + * already gives BITS_PER_LONG slots), the above boils down to + * 1. use the smallest power of two large enough to give us that many + * slots. + * 2. on 32bit skip 64 and 128 - the minimal capacity we want there is + * 256 slots (i.e. 1Kb fd array). + * 3. on 64bit don't skip anything, 1Kb fd array means 128 slots there + * and we are never going to be asked for 64 or less. */ - nr /= (1024 / sizeof(struct file *)); - nr = roundup_pow_of_two(nr + 1); - nr *= (1024 / sizeof(struct file *)); - nr = ALIGN(nr, BITS_PER_LONG); + if (IS_ENABLED(CONFIG_32BIT) && slots_wanted < 256) + nr = 256; + else + nr = roundup_pow_of_two(slots_wanted); /* * Note that this can drive nr *below* what we had passed if sysctl_nr_open - * had been set lower between the check in expand_files() and here. Deal - * with that in caller, it's cheaper that way. + * had been set lower between the check in expand_files() and here. * * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise * bitmaps handling below becomes unpleasant, to put it mildly... */ - if (unlikely(nr > sysctl_nr_open)) - nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; + if (unlikely(nr > sysctl_nr_open)) { + nr = round_down(sysctl_nr_open, BITS_PER_LONG); + if (nr < slots_wanted) + return ERR_PTR(-EMFILE); + } fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT); if (!fdt) @@ -152,14 +218,14 @@ out_arr: out_fdt: kfree(fdt); out: - return NULL; + return ERR_PTR(-ENOMEM); } /* * Expand the file descriptor table. * This function will allocate a new fdtable and both fd array and fdset, of * the given size. - * Return <0 error code on error; 1 on successful completion. + * Return <0 error code on error; 0 on successful completion. * The files->file_lock should be held on entry, and will be held on exit. */ static int expand_fdtable(struct files_struct *files, unsigned int nr) @@ -169,7 +235,7 @@ static int expand_fdtable(struct files_struct *files, unsigned int nr) struct fdtable *new_fdt, *cur_fdt; spin_unlock(&files->file_lock); - new_fdt = alloc_fdtable(nr); + new_fdt = alloc_fdtable(nr + 1); /* make sure all fd_install() have seen resize_in_progress * or have finished their rcu_read_lock_sched() section. @@ -178,16 +244,8 @@ static int expand_fdtable(struct files_struct *files, unsigned int nr) synchronize_rcu(); spin_lock(&files->file_lock); - if (!new_fdt) - return -ENOMEM; - /* - * extremely unlikely race - sysctl_nr_open decreased between the check in - * caller and alloc_fdtable(). Cheaper to catch it here... - */ - if (unlikely(new_fdt->max_fds <= nr)) { - __free_fdtable(new_fdt); - return -EMFILE; - } + if (IS_ERR(new_fdt)) + return PTR_ERR(new_fdt); cur_fdt = files_fdtable(files); BUG_ON(nr < cur_fdt->max_fds); copy_fdtable(new_fdt, cur_fdt); @@ -196,15 +254,14 @@ static int expand_fdtable(struct files_struct *files, unsigned int nr) call_rcu(&cur_fdt->rcu, free_fdtable_rcu); /* coupled with smp_rmb() in fd_install() */ smp_wmb(); - return 1; + return 0; } /* * Expand files. * This function will expand the file structures, if the requested size exceeds * the current capacity and there is room for expansion. - * Return <0 error code on error; 0 when nothing done; 1 when files were - * expanded and execution may have blocked. + * Return <0 error code on error; 0 on success. * The files->file_lock should be held on entry, and will be held on exit. */ static int expand_files(struct files_struct *files, unsigned int nr) @@ -212,14 +269,14 @@ static int expand_files(struct files_struct *files, unsigned int nr) __acquires(files->file_lock) { struct fdtable *fdt; - int expanded = 0; + int error; repeat: fdt = files_fdtable(files); /* Do we need to expand? */ if (nr < fdt->max_fds) - return expanded; + return 0; /* Can we expand? */ if (nr >= sysctl_nr_open) @@ -227,7 +284,6 @@ repeat: if (unlikely(files->resize_in_progress)) { spin_unlock(&files->file_lock); - expanded = 1; wait_event(files->resize_wait, !files->resize_in_progress); spin_lock(&files->file_lock); goto repeat; @@ -235,27 +291,28 @@ repeat: /* All good, so we try */ files->resize_in_progress = true; - expanded = expand_fdtable(files, nr); + error = expand_fdtable(files, nr); files->resize_in_progress = false; wake_up_all(&files->resize_wait); - return expanded; -} - -static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt) -{ - __set_bit(fd, fdt->close_on_exec); + return error; } -static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt) +static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt, + bool set) { - if (test_bit(fd, fdt->close_on_exec)) - __clear_bit(fd, fdt->close_on_exec); + if (set) { + __set_bit(fd, fdt->close_on_exec); + } else { + if (test_bit(fd, fdt->close_on_exec)) + __clear_bit(fd, fdt->close_on_exec); + } } -static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt) +static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt, bool set) { __set_bit(fd, fdt->open_fds); + __set_close_on_exec(fd, fdt, set); fd /= BITS_PER_LONG; if (!~fdt->open_fds[fd]) __set_bit(fd, fdt->full_fds_bits); @@ -264,7 +321,9 @@ static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt) static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt) { __clear_bit(fd, fdt->open_fds); - __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits); + fd /= BITS_PER_LONG; + if (test_bit(fd, fdt->full_fds_bits)) + __clear_bit(fd, fdt->full_fds_bits); } static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt) @@ -306,7 +365,6 @@ struct files_struct *dup_fd(struct files_struct *oldf, struct fd_range *punch_ho struct file **old_fds, **new_fds; unsigned int open_files, i; struct fdtable *old_fdt, *new_fdt; - int error; newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); if (!newf) @@ -338,17 +396,10 @@ struct files_struct *dup_fd(struct files_struct *oldf, struct fd_range *punch_ho if (new_fdt != &newf->fdtab) __free_fdtable(new_fdt); - new_fdt = alloc_fdtable(open_files - 1); - if (!new_fdt) { - error = -ENOMEM; - goto out_release; - } - - /* beyond sysctl_nr_open; nothing to do */ - if (unlikely(new_fdt->max_fds < open_files)) { - __free_fdtable(new_fdt); - error = -EMFILE; - goto out_release; + new_fdt = alloc_fdtable(open_files); + if (IS_ERR(new_fdt)) { + kmem_cache_free(files_cachep, newf); + return ERR_CAST(new_fdt); } /* @@ -389,10 +440,6 @@ struct files_struct *dup_fd(struct files_struct *oldf, struct fd_range *punch_ho rcu_assign_pointer(newf->fdt, new_fdt); return newf; - -out_release: - kmem_cache_free(files_cachep, newf); - return ERR_PTR(error); } static struct fdtable *close_files(struct files_struct * files) @@ -413,7 +460,7 @@ static struct fdtable *close_files(struct files_struct * files) set = fdt->open_fds[j++]; while (set) { if (set & 1) { - struct file * file = xchg(&fdt->fd[i], NULL); + struct file *file = fdt->fd[i]; if (file) { filp_close(file, files); cond_resched(); @@ -470,6 +517,15 @@ static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start) unsigned int maxfd = fdt->max_fds; /* always multiple of BITS_PER_LONG */ unsigned int maxbit = maxfd / BITS_PER_LONG; unsigned int bitbit = start / BITS_PER_LONG; + unsigned int bit; + + /* + * Try to avoid looking at the second level bitmap + */ + bit = find_next_zero_bit(&fdt->open_fds[bitbit], BITS_PER_LONG, + start & (BITS_PER_LONG - 1)); + if (bit < BITS_PER_LONG) + return bit + bitbit * BITS_PER_LONG; bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG; if (bitbit >= maxfd) @@ -496,7 +552,7 @@ 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); /* @@ -504,36 +560,22 @@ 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 (start <= files->next_fd) files->next_fd = fd + 1; - __set_open_fd(fd, fdt); - if (flags & O_CLOEXEC) - __set_close_on_exec(fd, fdt); - else - __clear_close_on_exec(fd, fdt); + __set_open_fd(fd, fdt, flags & O_CLOEXEC); 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 +641,7 @@ 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; @@ -713,7 +755,7 @@ static inline void __range_close(struct files_struct *files, unsigned int fd, } /** - * __close_range() - Close all file descriptors in a given range. + * sys_close_range() - Close all file descriptors in a given range. * * @fd: starting file descriptor to close * @max_fd: last file descriptor to close @@ -721,8 +763,10 @@ static inline void __range_close(struct files_struct *files, unsigned int fd, * * This closes a range of file descriptors. All file descriptors * from @fd up to and including @max_fd are closed. + * Currently, errors to close a given file descriptor are ignored. */ -int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) +SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd, + unsigned int, flags) { struct task_struct *me = current; struct files_struct *cur_fds = me->files, *fds = NULL; @@ -839,7 +883,7 @@ static struct file *__get_file_rcu(struct file __rcu **f) if (!file) return NULL; - if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) + if (unlikely(!file_ref_get(&file->f_ref))) return ERR_PTR(-EAGAIN); file_reloaded = rcu_dereference_raw(*f); @@ -853,8 +897,8 @@ static struct file *__get_file_rcu(struct file __rcu **f) OPTIMIZER_HIDE_VAR(file_reloaded_cmp); /* - * atomic_long_inc_not_zero() above provided a full memory - * barrier when we acquired a reference. + * file_ref_get() above provided a full memory barrier when we + * acquired a reference. * * This is paired with the write barrier from assigning to the * __rcu protected file pointer so that if that pointer still @@ -952,11 +996,11 @@ static inline struct file *__fget_files_rcu(struct files_struct *files, * We need to confirm it by incrementing the refcount * and then check the lookup again. * - * atomic_long_inc_not_zero() gives us a full memory - * barrier. We only really need an 'acquire' one to - * protect the loads below, but we don't have that. + * file_ref_get() gives us a full memory barrier. We + * only really need an 'acquire' one to protect the + * loads below, but we don't have that. */ - if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) + if (unlikely(!file_ref_get(&file->f_ref))) continue; /* @@ -1037,29 +1081,7 @@ struct file *fget_task(struct task_struct *task, unsigned int fd) return file; } -struct file *lookup_fdget_rcu(unsigned int fd) -{ - return __fget_files_rcu(current->files, fd, 0); - -} -EXPORT_SYMBOL_GPL(lookup_fdget_rcu); - -struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd) -{ - /* Must be called with rcu_read_lock held */ - struct files_struct *files; - struct file *file = NULL; - - task_lock(task); - files = task->files; - if (files) - file = __fget_files_rcu(files, fd, 0); - task_unlock(task); - - return file; -} - -struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *ret_fd) +struct file *fget_task_next(struct task_struct *task, unsigned int *ret_fd) { /* Must be called with rcu_read_lock held */ struct files_struct *files; @@ -1069,17 +1091,19 @@ struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int * task_lock(task); files = task->files; if (files) { + rcu_read_lock(); for (; fd < files_fdtable(files)->max_fds; fd++) { file = __fget_files_rcu(files, fd, 0); if (file) break; } + rcu_read_unlock(); } task_unlock(task); *ret_fd = fd; return file; } -EXPORT_SYMBOL(task_lookup_next_fdget_rcu); +EXPORT_SYMBOL(fget_task_next); /* * Lightweight file lookup - no refcnt increment if fd table isn't shared. @@ -1183,13 +1207,8 @@ void __f_unlock_pos(struct file *f) void set_close_on_exec(unsigned int fd, int flag) { struct files_struct *files = current->files; - struct fdtable *fdt; spin_lock(&files->file_lock); - fdt = files_fdtable(files); - if (flag) - __set_close_on_exec(fd, fdt); - else - __clear_close_on_exec(fd, fdt); + __set_close_on_exec(fd, files_fdtable(files), flag); spin_unlock(&files->file_lock); } @@ -1230,11 +1249,7 @@ __releases(&files->file_lock) goto Ebusy; get_file(file); rcu_assign_pointer(fdt->fd[fd], file); - __set_open_fd(fd, fdt); - if (flags & O_CLOEXEC) - __set_close_on_exec(fd, fdt); - else - __clear_close_on_exec(fd, fdt); + __set_open_fd(fd, fdt, flags & O_CLOEXEC); spin_unlock(&files->file_lock); if (tofree) |