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tmpfs: fix data loss from failed fallocate 

commit 44bcabd70cf1425b4243e02251c02b01638a8287
Author: Hugh Dickins <hughd@google.com>
Date:   Sun Dec 4 16:51:50 2022 -0800

    tmpfs: fix data loss from failed fallocate

    Fix tmpfs data loss when the fallocate system call is interrupted by a
    signal, or fails for some other reason.  The partial folio handling in
    shmem_undo_range() forgot to consider this unfalloc case, and was liable
    to erase or truncate out data which had already been committed earlier.

    It turns out that none of the partial folio handling there is appropriate
    for the unfalloc case, which just wants to proceed to removal of whole
    folios: which find_get_entries() provides, even when partially covered.

    Original patch by Rui Wang.

    Link: https://lore.kernel.org/linux-mm/33b85d82.7764.1842e9ab207.Coremail.chenguoqic@163.com/
    Link: https://lkml.kernel.org/r/a5dac112-cf4b-7af-a33-f386e347fd38@google.com
    Fixes: b9a8a4195c7d ("truncate,shmem: Handle truncates that split large folios")
    Signed-off-by: Hugh Dickins <hughd@google.com>
    Reported-by: Guoqi Chen <chenguoqic@163.com>
      Link: https://lore.kernel.org/all/20221101032248.819360-1-kernel@hev.cc/
    Cc: Rui Wang <kernel@hev.cc>
    Cc: Huacai Chen <chenhuacai@loongson.cn>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
    Cc: <stable@vger.kernel.org>    [5.17+]
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2168372
Signed-off-by: Nico Pache <npache@redhat.com>
This commit is contained in:
Nico Pache 2023-05-08 17:26:30 -06:00
parent 64a2336463
commit 9efa394ef3
1 changed files with 11 additions and 0 deletions
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11
mm/shmem.c
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@ -957,6 +957,15 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
index++;
}
/*
* When undoing a failed fallocate, we want none of the partial folio
* zeroing and splitting below, but shall want to truncate the whole
* folio when !uptodate indicates that it was added by this fallocate,
* even when [lstart, lend] covers only a part of the folio.
*/
if (unfalloc)
goto whole_folios;
same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
folio = shmem_get_partial_folio(inode, lstart >> PAGE_SHIFT);
if (folio) {
@ -982,6 +991,8 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
folio_put(folio);
}
whole_folios:
index = start;
while (index < end) {
cond_resched();