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author | Al Viro <viro@zeniv.linux.org.uk> | 2021-05-31 00:32:44 -0400 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2021-06-02 17:50:44 -0400 |
commit | bc1bb416bbb9203e250f5c49aaf1d11b5d9c8adb (patch) | |
tree | 2d978ab21227c4f1e9de120f1ecab5b110e56144 /fs/iomap | |
parent | 9067931236651c8bde847d17a2f862d052e672b7 (diff) | |
download | linux-stable-bc1bb416bbb9203e250f5c49aaf1d11b5d9c8adb.tar.gz linux-stable-bc1bb416bbb9203e250f5c49aaf1d11b5d9c8adb.tar.bz2 linux-stable-bc1bb416bbb9203e250f5c49aaf1d11b5d9c8adb.zip |
generic_perform_write()/iomap_write_actor(): saner logics for short copy
if we run into a short copy and ->write_end() refuses to advance at all,
use the amount we'd managed to copy for the next iteration to handle.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/iomap')
-rw-r--r-- | fs/iomap/buffered-io.c | 25 |
1 files changed, 10 insertions, 15 deletions
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index f2cd2034a87b..354b41d20e5d 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -771,10 +771,6 @@ again: * Otherwise there's a nasty deadlock on copying from the * same page as we're writing to, without it being marked * up-to-date. - * - * Not only is this an optimisation, but it is also required - * to check that the address is actually valid, when atomic - * usercopies are used, below. */ if (unlikely(iov_iter_fault_in_readable(i, bytes))) { status = -EFAULT; @@ -791,25 +787,24 @@ again: copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); - copied = iomap_write_end(inode, pos, bytes, copied, page, iomap, + status = iomap_write_end(inode, pos, bytes, copied, page, iomap, srcmap); cond_resched(); - iov_iter_advance(i, copied); - if (unlikely(copied == 0)) { + if (unlikely(status == 0)) { /* - * If we were unable to copy any data at all, we must - * fall back to a single segment length write. - * - * If we didn't fallback here, we could livelock - * because not all segments in the iov can be copied at - * once without a pagefault. + * A short copy made iomap_write_end() reject the + * thing entirely. Might be memory poisoning + * halfway through, might be a race with munmap, + * might be severe memory pressure. */ - bytes = min_t(unsigned long, PAGE_SIZE - offset, - iov_iter_single_seg_count(i)); + if (copied) + bytes = copied; goto again; } + copied = status; + iov_iter_advance(i, copied); pos += copied; written += copied; length -= copied; |