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Linux/fs/ext4/file.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  linux/fs/ext4/file.c
  4  *
  5  * Copyright (C) 1992, 1993, 1994, 1995
  6  * Remy Card (card@masi.ibp.fr)
  7  * Laboratoire MASI - Institut Blaise Pascal
  8  * Universite Pierre et Marie Curie (Paris VI)
  9  *
 10  *  from
 11  *
 12  *  linux/fs/minix/file.c
 13  *
 14  *  Copyright (C) 1991, 1992  Linus Torvalds
 15  *
 16  *  ext4 fs regular file handling primitives
 17  *
 18  *  64-bit file support on 64-bit platforms by Jakub Jelinek
 19  *      (jj@sunsite.ms.mff.cuni.cz)
 20  */
 21 
 22 #include <linux/time.h>
 23 #include <linux/fs.h>
 24 #include <linux/iomap.h>
 25 #include <linux/mount.h>
 26 #include <linux/path.h>
 27 #include <linux/dax.h>
 28 #include <linux/quotaops.h>
 29 #include <linux/pagevec.h>
 30 #include <linux/uio.h>
 31 #include <linux/mman.h>
 32 #include "ext4.h"
 33 #include "ext4_jbd2.h"
 34 #include "xattr.h"
 35 #include "acl.h"
 36 
 37 #ifdef CONFIG_FS_DAX
 38 static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 39 {
 40         struct inode *inode = file_inode(iocb->ki_filp);
 41         ssize_t ret;
 42 
 43         if (!inode_trylock_shared(inode)) {
 44                 if (iocb->ki_flags & IOCB_NOWAIT)
 45                         return -EAGAIN;
 46                 inode_lock_shared(inode);
 47         }
 48         /*
 49          * Recheck under inode lock - at this point we are sure it cannot
 50          * change anymore
 51          */
 52         if (!IS_DAX(inode)) {
 53                 inode_unlock_shared(inode);
 54                 /* Fallback to buffered IO in case we cannot support DAX */
 55                 return generic_file_read_iter(iocb, to);
 56         }
 57         ret = dax_iomap_rw(iocb, to, &ext4_iomap_ops);
 58         inode_unlock_shared(inode);
 59 
 60         file_accessed(iocb->ki_filp);
 61         return ret;
 62 }
 63 #endif
 64 
 65 static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 66 {
 67         if (unlikely(ext4_forced_shutdown(EXT4_SB(file_inode(iocb->ki_filp)->i_sb))))
 68                 return -EIO;
 69 
 70         if (!iov_iter_count(to))
 71                 return 0; /* skip atime */
 72 
 73 #ifdef CONFIG_FS_DAX
 74         if (IS_DAX(file_inode(iocb->ki_filp)))
 75                 return ext4_dax_read_iter(iocb, to);
 76 #endif
 77         return generic_file_read_iter(iocb, to);
 78 }
 79 
 80 /*
 81  * Called when an inode is released. Note that this is different
 82  * from ext4_file_open: open gets called at every open, but release
 83  * gets called only when /all/ the files are closed.
 84  */
 85 static int ext4_release_file(struct inode *inode, struct file *filp)
 86 {
 87         if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
 88                 ext4_alloc_da_blocks(inode);
 89                 ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
 90         }
 91         /* if we are the last writer on the inode, drop the block reservation */
 92         if ((filp->f_mode & FMODE_WRITE) &&
 93                         (atomic_read(&inode->i_writecount) == 1) &&
 94                         !EXT4_I(inode)->i_reserved_data_blocks)
 95         {
 96                 down_write(&EXT4_I(inode)->i_data_sem);
 97                 ext4_discard_preallocations(inode);
 98                 up_write(&EXT4_I(inode)->i_data_sem);
 99         }
100         if (is_dx(inode) && filp->private_data)
101                 ext4_htree_free_dir_info(filp->private_data);
102 
103         return 0;
104 }
105 
106 static void ext4_unwritten_wait(struct inode *inode)
107 {
108         wait_queue_head_t *wq = ext4_ioend_wq(inode);
109 
110         wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
111 }
112 
113 /*
114  * This tests whether the IO in question is block-aligned or not.
115  * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
116  * are converted to written only after the IO is complete.  Until they are
117  * mapped, these blocks appear as holes, so dio_zero_block() will assume that
118  * it needs to zero out portions of the start and/or end block.  If 2 AIO
119  * threads are at work on the same unwritten block, they must be synchronized
120  * or one thread will zero the other's data, causing corruption.
121  */
122 static int
123 ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
124 {
125         struct super_block *sb = inode->i_sb;
126         int blockmask = sb->s_blocksize - 1;
127 
128         if (pos >= ALIGN(i_size_read(inode), sb->s_blocksize))
129                 return 0;
130 
131         if ((pos | iov_iter_alignment(from)) & blockmask)
132                 return 1;
133 
134         return 0;
135 }
136 
137 /* Is IO overwriting allocated and initialized blocks? */
138 static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
139 {
140         struct ext4_map_blocks map;
141         unsigned int blkbits = inode->i_blkbits;
142         int err, blklen;
143 
144         if (pos + len > i_size_read(inode))
145                 return false;
146 
147         map.m_lblk = pos >> blkbits;
148         map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
149         blklen = map.m_len;
150 
151         err = ext4_map_blocks(NULL, inode, &map, 0);
152         /*
153          * 'err==len' means that all of the blocks have been preallocated,
154          * regardless of whether they have been initialized or not. To exclude
155          * unwritten extents, we need to check m_flags.
156          */
157         return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
158 }
159 
160 static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
161 {
162         struct inode *inode = file_inode(iocb->ki_filp);
163         ssize_t ret;
164 
165         ret = generic_write_checks(iocb, from);
166         if (ret <= 0)
167                 return ret;
168         /*
169          * If we have encountered a bitmap-format file, the size limit
170          * is smaller than s_maxbytes, which is for extent-mapped files.
171          */
172         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
173                 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
174 
175                 if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
176                         return -EFBIG;
177                 iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
178         }
179         return iov_iter_count(from);
180 }
181 
182 #ifdef CONFIG_FS_DAX
183 static ssize_t
184 ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
185 {
186         struct inode *inode = file_inode(iocb->ki_filp);
187         ssize_t ret;
188 
189         if (!inode_trylock(inode)) {
190                 if (iocb->ki_flags & IOCB_NOWAIT)
191                         return -EAGAIN;
192                 inode_lock(inode);
193         }
194         ret = ext4_write_checks(iocb, from);
195         if (ret <= 0)
196                 goto out;
197         ret = file_remove_privs(iocb->ki_filp);
198         if (ret)
199                 goto out;
200         ret = file_update_time(iocb->ki_filp);
201         if (ret)
202                 goto out;
203 
204         ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
205 out:
206         inode_unlock(inode);
207         if (ret > 0)
208                 ret = generic_write_sync(iocb, ret);
209         return ret;
210 }
211 #endif
212 
213 static ssize_t
214 ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
215 {
216         struct inode *inode = file_inode(iocb->ki_filp);
217         int o_direct = iocb->ki_flags & IOCB_DIRECT;
218         int unaligned_aio = 0;
219         int overwrite = 0;
220         ssize_t ret;
221 
222         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
223                 return -EIO;
224 
225 #ifdef CONFIG_FS_DAX
226         if (IS_DAX(inode))
227                 return ext4_dax_write_iter(iocb, from);
228 #endif
229         if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
230                 return -EOPNOTSUPP;
231 
232         if (!inode_trylock(inode)) {
233                 if (iocb->ki_flags & IOCB_NOWAIT)
234                         return -EAGAIN;
235                 inode_lock(inode);
236         }
237 
238         ret = ext4_write_checks(iocb, from);
239         if (ret <= 0)
240                 goto out;
241 
242         /*
243          * Unaligned direct AIO must be serialized among each other as zeroing
244          * of partial blocks of two competing unaligned AIOs can result in data
245          * corruption.
246          */
247         if (o_direct && ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
248             !is_sync_kiocb(iocb) &&
249             ext4_unaligned_aio(inode, from, iocb->ki_pos)) {
250                 unaligned_aio = 1;
251                 ext4_unwritten_wait(inode);
252         }
253 
254         iocb->private = &overwrite;
255         /* Check whether we do a DIO overwrite or not */
256         if (o_direct && !unaligned_aio) {
257                 if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
258                         if (ext4_should_dioread_nolock(inode))
259                                 overwrite = 1;
260                 } else if (iocb->ki_flags & IOCB_NOWAIT) {
261                         ret = -EAGAIN;
262                         goto out;
263                 }
264         }
265 
266         ret = __generic_file_write_iter(iocb, from);
267         /*
268          * Unaligned direct AIO must be the only IO in flight. Otherwise
269          * overlapping aligned IO after unaligned might result in data
270          * corruption.
271          */
272         if (ret == -EIOCBQUEUED && unaligned_aio)
273                 ext4_unwritten_wait(inode);
274         inode_unlock(inode);
275 
276         if (ret > 0)
277                 ret = generic_write_sync(iocb, ret);
278 
279         return ret;
280 
281 out:
282         inode_unlock(inode);
283         return ret;
284 }
285 
286 #ifdef CONFIG_FS_DAX
287 static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,
288                 enum page_entry_size pe_size)
289 {
290         int error = 0;
291         vm_fault_t result;
292         int retries = 0;
293         handle_t *handle = NULL;
294         struct inode *inode = file_inode(vmf->vma->vm_file);
295         struct super_block *sb = inode->i_sb;
296 
297         /*
298          * We have to distinguish real writes from writes which will result in a
299          * COW page; COW writes should *not* poke the journal (the file will not
300          * be changed). Doing so would cause unintended failures when mounted
301          * read-only.
302          *
303          * We check for VM_SHARED rather than vmf->cow_page since the latter is
304          * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
305          * other sizes, dax_iomap_fault will handle splitting / fallback so that
306          * we eventually come back with a COW page.
307          */
308         bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
309                 (vmf->vma->vm_flags & VM_SHARED);
310         pfn_t pfn;
311 
312         if (write) {
313                 sb_start_pagefault(sb);
314                 file_update_time(vmf->vma->vm_file);
315                 down_read(&EXT4_I(inode)->i_mmap_sem);
316 retry:
317                 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
318                                                EXT4_DATA_TRANS_BLOCKS(sb));
319                 if (IS_ERR(handle)) {
320                         up_read(&EXT4_I(inode)->i_mmap_sem);
321                         sb_end_pagefault(sb);
322                         return VM_FAULT_SIGBUS;
323                 }
324         } else {
325                 down_read(&EXT4_I(inode)->i_mmap_sem);
326         }
327         result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
328         if (write) {
329                 ext4_journal_stop(handle);
330 
331                 if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
332                     ext4_should_retry_alloc(sb, &retries))
333                         goto retry;
334                 /* Handling synchronous page fault? */
335                 if (result & VM_FAULT_NEEDDSYNC)
336                         result = dax_finish_sync_fault(vmf, pe_size, pfn);
337                 up_read(&EXT4_I(inode)->i_mmap_sem);
338                 sb_end_pagefault(sb);
339         } else {
340                 up_read(&EXT4_I(inode)->i_mmap_sem);
341         }
342 
343         return result;
344 }
345 
346 static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)
347 {
348         return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
349 }
350 
351 static const struct vm_operations_struct ext4_dax_vm_ops = {
352         .fault          = ext4_dax_fault,
353         .huge_fault     = ext4_dax_huge_fault,
354         .page_mkwrite   = ext4_dax_fault,
355         .pfn_mkwrite    = ext4_dax_fault,
356 };
357 #else
358 #define ext4_dax_vm_ops ext4_file_vm_ops
359 #endif
360 
361 static const struct vm_operations_struct ext4_file_vm_ops = {
362         .fault          = ext4_filemap_fault,
363         .map_pages      = filemap_map_pages,
364         .page_mkwrite   = ext4_page_mkwrite,
365 };
366 
367 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
368 {
369         struct inode *inode = file->f_mapping->host;
370 
371         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
372                 return -EIO;
373 
374         /*
375          * We don't support synchronous mappings for non-DAX files. At least
376          * until someone comes with a sensible use case.
377          */
378         if (!IS_DAX(file_inode(file)) && (vma->vm_flags & VM_SYNC))
379                 return -EOPNOTSUPP;
380 
381         file_accessed(file);
382         if (IS_DAX(file_inode(file))) {
383                 vma->vm_ops = &ext4_dax_vm_ops;
384                 vma->vm_flags |= VM_HUGEPAGE;
385         } else {
386                 vma->vm_ops = &ext4_file_vm_ops;
387         }
388         return 0;
389 }
390 
391 static int ext4_sample_last_mounted(struct super_block *sb,
392                                     struct vfsmount *mnt)
393 {
394         struct ext4_sb_info *sbi = EXT4_SB(sb);
395         struct path path;
396         char buf[64], *cp;
397         handle_t *handle;
398         int err;
399 
400         if (likely(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED))
401                 return 0;
402 
403         if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))
404                 return 0;
405 
406         sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
407         /*
408          * Sample where the filesystem has been mounted and
409          * store it in the superblock for sysadmin convenience
410          * when trying to sort through large numbers of block
411          * devices or filesystem images.
412          */
413         memset(buf, 0, sizeof(buf));
414         path.mnt = mnt;
415         path.dentry = mnt->mnt_root;
416         cp = d_path(&path, buf, sizeof(buf));
417         err = 0;
418         if (IS_ERR(cp))
419                 goto out;
420 
421         handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
422         err = PTR_ERR(handle);
423         if (IS_ERR(handle))
424                 goto out;
425         BUFFER_TRACE(sbi->s_sbh, "get_write_access");
426         err = ext4_journal_get_write_access(handle, sbi->s_sbh);
427         if (err)
428                 goto out_journal;
429         strlcpy(sbi->s_es->s_last_mounted, cp,
430                 sizeof(sbi->s_es->s_last_mounted));
431         ext4_handle_dirty_super(handle, sb);
432 out_journal:
433         ext4_journal_stop(handle);
434 out:
435         sb_end_intwrite(sb);
436         return err;
437 }
438 
439 static int ext4_file_open(struct inode * inode, struct file * filp)
440 {
441         int ret;
442 
443         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
444                 return -EIO;
445 
446         ret = ext4_sample_last_mounted(inode->i_sb, filp->f_path.mnt);
447         if (ret)
448                 return ret;
449 
450         ret = fscrypt_file_open(inode, filp);
451         if (ret)
452                 return ret;
453 
454         /*
455          * Set up the jbd2_inode if we are opening the inode for
456          * writing and the journal is present
457          */
458         if (filp->f_mode & FMODE_WRITE) {
459                 ret = ext4_inode_attach_jinode(inode);
460                 if (ret < 0)
461                         return ret;
462         }
463 
464         filp->f_mode |= FMODE_NOWAIT;
465         return dquot_file_open(inode, filp);
466 }
467 
468 /*
469  * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
470  * by calling generic_file_llseek_size() with the appropriate maxbytes
471  * value for each.
472  */
473 loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
474 {
475         struct inode *inode = file->f_mapping->host;
476         loff_t maxbytes;
477 
478         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
479                 maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
480         else
481                 maxbytes = inode->i_sb->s_maxbytes;
482 
483         switch (whence) {
484         default:
485                 return generic_file_llseek_size(file, offset, whence,
486                                                 maxbytes, i_size_read(inode));
487         case SEEK_HOLE:
488                 inode_lock_shared(inode);
489                 offset = iomap_seek_hole(inode, offset, &ext4_iomap_ops);
490                 inode_unlock_shared(inode);
491                 break;
492         case SEEK_DATA:
493                 inode_lock_shared(inode);
494                 offset = iomap_seek_data(inode, offset, &ext4_iomap_ops);
495                 inode_unlock_shared(inode);
496                 break;
497         }
498 
499         if (offset < 0)
500                 return offset;
501         return vfs_setpos(file, offset, maxbytes);
502 }
503 
504 const struct file_operations ext4_file_operations = {
505         .llseek         = ext4_llseek,
506         .read_iter      = ext4_file_read_iter,
507         .write_iter     = ext4_file_write_iter,
508         .unlocked_ioctl = ext4_ioctl,
509 #ifdef CONFIG_COMPAT
510         .compat_ioctl   = ext4_compat_ioctl,
511 #endif
512         .mmap           = ext4_file_mmap,
513         .mmap_supported_flags = MAP_SYNC,
514         .open           = ext4_file_open,
515         .release        = ext4_release_file,
516         .fsync          = ext4_sync_file,
517         .get_unmapped_area = thp_get_unmapped_area,
518         .splice_read    = generic_file_splice_read,
519         .splice_write   = iter_file_splice_write,
520         .fallocate      = ext4_fallocate,
521 };
522 
523 const struct inode_operations ext4_file_inode_operations = {
524         .setattr        = ext4_setattr,
525         .getattr        = ext4_file_getattr,
526         .listxattr      = ext4_listxattr,
527         .get_acl        = ext4_get_acl,
528         .set_acl        = ext4_set_acl,
529         .fiemap         = ext4_fiemap,
530 };
531 
532 

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