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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 (unlikely(IS_IMMUTABLE(inode)))
170                 return -EPERM;
171 
172         /*
173          * If we have encountered a bitmap-format file, the size limit
174          * is smaller than s_maxbytes, which is for extent-mapped files.
175          */
176         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
177                 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
178 
179                 if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
180                         return -EFBIG;
181                 iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
182         }
183         return iov_iter_count(from);
184 }
185 
186 #ifdef CONFIG_FS_DAX
187 static ssize_t
188 ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
189 {
190         struct inode *inode = file_inode(iocb->ki_filp);
191         ssize_t ret;
192 
193         if (!inode_trylock(inode)) {
194                 if (iocb->ki_flags & IOCB_NOWAIT)
195                         return -EAGAIN;
196                 inode_lock(inode);
197         }
198         ret = ext4_write_checks(iocb, from);
199         if (ret <= 0)
200                 goto out;
201         ret = file_remove_privs(iocb->ki_filp);
202         if (ret)
203                 goto out;
204         ret = file_update_time(iocb->ki_filp);
205         if (ret)
206                 goto out;
207 
208         ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
209 out:
210         inode_unlock(inode);
211         if (ret > 0)
212                 ret = generic_write_sync(iocb, ret);
213         return ret;
214 }
215 #endif
216 
217 static ssize_t
218 ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
219 {
220         struct inode *inode = file_inode(iocb->ki_filp);
221         int o_direct = iocb->ki_flags & IOCB_DIRECT;
222         int unaligned_aio = 0;
223         int overwrite = 0;
224         ssize_t ret;
225 
226         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
227                 return -EIO;
228 
229 #ifdef CONFIG_FS_DAX
230         if (IS_DAX(inode))
231                 return ext4_dax_write_iter(iocb, from);
232 #endif
233         if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
234                 return -EOPNOTSUPP;
235 
236         if (!inode_trylock(inode)) {
237                 if (iocb->ki_flags & IOCB_NOWAIT)
238                         return -EAGAIN;
239                 inode_lock(inode);
240         }
241 
242         ret = ext4_write_checks(iocb, from);
243         if (ret <= 0)
244                 goto out;
245 
246         /*
247          * Unaligned direct AIO must be serialized among each other as zeroing
248          * of partial blocks of two competing unaligned AIOs can result in data
249          * corruption.
250          */
251         if (o_direct && ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
252             !is_sync_kiocb(iocb) &&
253             ext4_unaligned_aio(inode, from, iocb->ki_pos)) {
254                 unaligned_aio = 1;
255                 ext4_unwritten_wait(inode);
256         }
257 
258         iocb->private = &overwrite;
259         /* Check whether we do a DIO overwrite or not */
260         if (o_direct && !unaligned_aio) {
261                 if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
262                         if (ext4_should_dioread_nolock(inode))
263                                 overwrite = 1;
264                 } else if (iocb->ki_flags & IOCB_NOWAIT) {
265                         ret = -EAGAIN;
266                         goto out;
267                 }
268         }
269 
270         ret = __generic_file_write_iter(iocb, from);
271         /*
272          * Unaligned direct AIO must be the only IO in flight. Otherwise
273          * overlapping aligned IO after unaligned might result in data
274          * corruption.
275          */
276         if (ret == -EIOCBQUEUED && unaligned_aio)
277                 ext4_unwritten_wait(inode);
278         inode_unlock(inode);
279 
280         if (ret > 0)
281                 ret = generic_write_sync(iocb, ret);
282 
283         return ret;
284 
285 out:
286         inode_unlock(inode);
287         return ret;
288 }
289 
290 #ifdef CONFIG_FS_DAX
291 static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,
292                 enum page_entry_size pe_size)
293 {
294         int error = 0;
295         vm_fault_t result;
296         int retries = 0;
297         handle_t *handle = NULL;
298         struct inode *inode = file_inode(vmf->vma->vm_file);
299         struct super_block *sb = inode->i_sb;
300 
301         /*
302          * We have to distinguish real writes from writes which will result in a
303          * COW page; COW writes should *not* poke the journal (the file will not
304          * be changed). Doing so would cause unintended failures when mounted
305          * read-only.
306          *
307          * We check for VM_SHARED rather than vmf->cow_page since the latter is
308          * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
309          * other sizes, dax_iomap_fault will handle splitting / fallback so that
310          * we eventually come back with a COW page.
311          */
312         bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
313                 (vmf->vma->vm_flags & VM_SHARED);
314         pfn_t pfn;
315 
316         if (write) {
317                 sb_start_pagefault(sb);
318                 file_update_time(vmf->vma->vm_file);
319                 down_read(&EXT4_I(inode)->i_mmap_sem);
320 retry:
321                 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
322                                                EXT4_DATA_TRANS_BLOCKS(sb));
323                 if (IS_ERR(handle)) {
324                         up_read(&EXT4_I(inode)->i_mmap_sem);
325                         sb_end_pagefault(sb);
326                         return VM_FAULT_SIGBUS;
327                 }
328         } else {
329                 down_read(&EXT4_I(inode)->i_mmap_sem);
330         }
331         result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
332         if (write) {
333                 ext4_journal_stop(handle);
334 
335                 if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
336                     ext4_should_retry_alloc(sb, &retries))
337                         goto retry;
338                 /* Handling synchronous page fault? */
339                 if (result & VM_FAULT_NEEDDSYNC)
340                         result = dax_finish_sync_fault(vmf, pe_size, pfn);
341                 up_read(&EXT4_I(inode)->i_mmap_sem);
342                 sb_end_pagefault(sb);
343         } else {
344                 up_read(&EXT4_I(inode)->i_mmap_sem);
345         }
346 
347         return result;
348 }
349 
350 static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)
351 {
352         return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
353 }
354 
355 static const struct vm_operations_struct ext4_dax_vm_ops = {
356         .fault          = ext4_dax_fault,
357         .huge_fault     = ext4_dax_huge_fault,
358         .page_mkwrite   = ext4_dax_fault,
359         .pfn_mkwrite    = ext4_dax_fault,
360 };
361 #else
362 #define ext4_dax_vm_ops ext4_file_vm_ops
363 #endif
364 
365 static const struct vm_operations_struct ext4_file_vm_ops = {
366         .fault          = ext4_filemap_fault,
367         .map_pages      = filemap_map_pages,
368         .page_mkwrite   = ext4_page_mkwrite,
369 };
370 
371 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
372 {
373         struct inode *inode = file->f_mapping->host;
374         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
375         struct dax_device *dax_dev = sbi->s_daxdev;
376 
377         if (unlikely(ext4_forced_shutdown(sbi)))
378                 return -EIO;
379 
380         /*
381          * We don't support synchronous mappings for non-DAX files and
382          * for DAX files if underneath dax_device is not synchronous.
383          */
384         if (!daxdev_mapping_supported(vma, dax_dev))
385                 return -EOPNOTSUPP;
386 
387         file_accessed(file);
388         if (IS_DAX(file_inode(file))) {
389                 vma->vm_ops = &ext4_dax_vm_ops;
390                 vma->vm_flags |= VM_HUGEPAGE;
391         } else {
392                 vma->vm_ops = &ext4_file_vm_ops;
393         }
394         return 0;
395 }
396 
397 static int ext4_sample_last_mounted(struct super_block *sb,
398                                     struct vfsmount *mnt)
399 {
400         struct ext4_sb_info *sbi = EXT4_SB(sb);
401         struct path path;
402         char buf[64], *cp;
403         handle_t *handle;
404         int err;
405 
406         if (likely(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED))
407                 return 0;
408 
409         if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))
410                 return 0;
411 
412         sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
413         /*
414          * Sample where the filesystem has been mounted and
415          * store it in the superblock for sysadmin convenience
416          * when trying to sort through large numbers of block
417          * devices or filesystem images.
418          */
419         memset(buf, 0, sizeof(buf));
420         path.mnt = mnt;
421         path.dentry = mnt->mnt_root;
422         cp = d_path(&path, buf, sizeof(buf));
423         err = 0;
424         if (IS_ERR(cp))
425                 goto out;
426 
427         handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
428         err = PTR_ERR(handle);
429         if (IS_ERR(handle))
430                 goto out;
431         BUFFER_TRACE(sbi->s_sbh, "get_write_access");
432         err = ext4_journal_get_write_access(handle, sbi->s_sbh);
433         if (err)
434                 goto out_journal;
435         strlcpy(sbi->s_es->s_last_mounted, cp,
436                 sizeof(sbi->s_es->s_last_mounted));
437         ext4_handle_dirty_super(handle, sb);
438 out_journal:
439         ext4_journal_stop(handle);
440 out:
441         sb_end_intwrite(sb);
442         return err;
443 }
444 
445 static int ext4_file_open(struct inode * inode, struct file * filp)
446 {
447         int ret;
448 
449         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
450                 return -EIO;
451 
452         ret = ext4_sample_last_mounted(inode->i_sb, filp->f_path.mnt);
453         if (ret)
454                 return ret;
455 
456         ret = fscrypt_file_open(inode, filp);
457         if (ret)
458                 return ret;
459 
460         /*
461          * Set up the jbd2_inode if we are opening the inode for
462          * writing and the journal is present
463          */
464         if (filp->f_mode & FMODE_WRITE) {
465                 ret = ext4_inode_attach_jinode(inode);
466                 if (ret < 0)
467                         return ret;
468         }
469 
470         filp->f_mode |= FMODE_NOWAIT;
471         return dquot_file_open(inode, filp);
472 }
473 
474 /*
475  * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
476  * by calling generic_file_llseek_size() with the appropriate maxbytes
477  * value for each.
478  */
479 loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
480 {
481         struct inode *inode = file->f_mapping->host;
482         loff_t maxbytes;
483 
484         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
485                 maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
486         else
487                 maxbytes = inode->i_sb->s_maxbytes;
488 
489         switch (whence) {
490         default:
491                 return generic_file_llseek_size(file, offset, whence,
492                                                 maxbytes, i_size_read(inode));
493         case SEEK_HOLE:
494                 inode_lock_shared(inode);
495                 offset = iomap_seek_hole(inode, offset, &ext4_iomap_ops);
496                 inode_unlock_shared(inode);
497                 break;
498         case SEEK_DATA:
499                 inode_lock_shared(inode);
500                 offset = iomap_seek_data(inode, offset, &ext4_iomap_ops);
501                 inode_unlock_shared(inode);
502                 break;
503         }
504 
505         if (offset < 0)
506                 return offset;
507         return vfs_setpos(file, offset, maxbytes);
508 }
509 
510 const struct file_operations ext4_file_operations = {
511         .llseek         = ext4_llseek,
512         .read_iter      = ext4_file_read_iter,
513         .write_iter     = ext4_file_write_iter,
514         .unlocked_ioctl = ext4_ioctl,
515 #ifdef CONFIG_COMPAT
516         .compat_ioctl   = ext4_compat_ioctl,
517 #endif
518         .mmap           = ext4_file_mmap,
519         .mmap_supported_flags = MAP_SYNC,
520         .open           = ext4_file_open,
521         .release        = ext4_release_file,
522         .fsync          = ext4_sync_file,
523         .get_unmapped_area = thp_get_unmapped_area,
524         .splice_read    = generic_file_splice_read,
525         .splice_write   = iter_file_splice_write,
526         .fallocate      = ext4_fallocate,
527 };
528 
529 const struct inode_operations ext4_file_inode_operations = {
530         .setattr        = ext4_setattr,
531         .getattr        = ext4_file_getattr,
532         .listxattr      = ext4_listxattr,
533         .get_acl        = ext4_get_acl,
534         .set_acl        = ext4_set_acl,
535         .fiemap         = ext4_fiemap,
536 };
537 
538 

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