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Commit 7d8a45695cc8f9fcdf4121fcbd897ecb63f758e4

Authored by Will Deacon
Committed by Linus Torvalds
1 parent 4e791c98ae
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

ipc: shm: restore MADV_REMOVE functionality on shared memory segments 

Commit 17cf28afea2a ("mm/fs: remove truncate_range") removed the
truncate_range inode operation in favour of the fallocate file
operation.

When using SYSV IPC shared memory segments, calling madvise with the
MADV_REMOVE advice on an area of shared memory will attempt to invoke
the .fallocate function for the shm_file_operations, which is NULL and
therefore returns -EOPNOTSUPP to userspace.  The previous behaviour
would inherit the inode_operations from the underlying tmpfs file and
invoke truncate_range there.

This patch restores the previous behaviour by wrapping the underlying
fallocate function in shm_fallocate, as we do for fsync.

[hughd@google.com: use -ENOTSUPP in shm_fallocate()]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 12 additions and 0 deletions Side-by-side Diff

... ... @@ -393,6 +393,16 @@
393 393 return sfd->file->f_op->fsync(sfd->file, start, end, datasync);
394 394 }
395 395  
  396 +static long shm_fallocate(struct file *file, int mode, loff_t offset,
  397 + loff_t len)
  398 +{
  399 + struct shm_file_data *sfd = shm_file_data(file);
  400 +
  401 + if (!sfd->file->f_op->fallocate)
  402 + return -EOPNOTSUPP;
  403 + return sfd->file->f_op->fallocate(file, mode, offset, len);
  404 +}
  405 +
396 406 static unsigned long shm_get_unmapped_area(struct file *file,
397 407 unsigned long addr, unsigned long len, unsigned long pgoff,
398 408 unsigned long flags)
... ... @@ -410,6 +420,7 @@
410 420 .get_unmapped_area = shm_get_unmapped_area,
411 421 #endif
412 422 .llseek = noop_llseek,
  423 + .fallocate = shm_fallocate,
413 424 };
414 425  
415 426 static const struct file_operations shm_file_operations_huge = {
... ... @@ -418,6 +429,7 @@
418 429 .release = shm_release,
419 430 .get_unmapped_area = shm_get_unmapped_area,
420 431 .llseek = noop_llseek,
  432 + .fallocate = shm_fallocate,
421 433 };
422 434  
423 435 int is_file_shm_hugepages(struct file *file)