The patch titled Subject: tmpfs: fix data loss from failed fallocate has been added to the -mm mm-hotfixes-unstable branch. Its filename is tmpfs-fix-data-loss-from-failed-fallocate.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Hugh Dickins hughd@google.com Subject: tmpfs: fix data loss from failed fallocate Date: Sun, 4 Dec 2022 16:51:50 -0800 (PST)

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.chenguoq... 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 ---

mm/shmem.c | 11 +++++++++++ 1 file changed, 11 insertions(+)

--- a/mm/shmem.c~tmpfs-fix-data-loss-from-failed-fallocate +++ a/mm/shmem.c @@ -948,6 +948,15 @@ static void shmem_undo_range(struct inod 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) { @@ -973,6 +982,8 @@ static void shmem_undo_range(struct inod folio_put(folio); }

+whole_folios: + index = start; while (index < end) { cond_resched(); _

Patches currently in -mm which might be from hughd@google.com are

tmpfs-fix-data-loss-from-failed-fallocate.patch