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    SubjectRe: [RFC 4/8] jbd, jbd2: Do not fail journal because of frozen_buffer allocation failure
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    mhocko@kernel.org wrote:

    > From: Michal Hocko <mhocko@suse.com>
    >
    > Journal transaction might fail prematurely because the frozen_buffer
    > is allocated by GFP_NOFS request:
    > [ 72.440013] do_get_write_access: OOM for frozen_buffer
    > [ 72.440014] EXT4-fs: ext4_reserve_inode_write:4729: aborting transaction: Out of memory in __ext4_journal_get_write_access
    > [ 72.440015] EXT4-fs error (device sda1) in ext4_reserve_inode_write:4735: Out of memory
    > (...snipped....)
    > [ 72.495559] do_get_write_access: OOM for frozen_buffer
    > [ 72.495560] EXT4-fs: ext4_reserve_inode_write:4729: aborting transaction: Out of memory in __ext4_journal_get_write_access
    > [ 72.496839] do_get_write_access: OOM for frozen_buffer
    > [ 72.496841] EXT4-fs: ext4_reserve_inode_write:4729: aborting transaction: Out of memory in __ext4_journal_get_write_access
    > [ 72.505766] Aborting journal on device sda1-8.
    > [ 72.505851] EXT4-fs (sda1): Remounting filesystem read-only
    >
    > This wasn't a problem until "mm: page_alloc: do not lock up GFP_NOFS
    > allocations upon OOM" because small GPF_NOFS allocations never failed.
    > This allocation seems essential for the journal and GFP_NOFS is too
    > restrictive to the memory allocator so let's use __GFP_NOFAIL here to
    > emulate the previous behavior.
    >
    > jbd code has the very same issue so let's do the same there as well.
    >
    > Signed-off-by: Michal Hocko <mhocko@suse.com>
    > ---
    > fs/jbd/transaction.c | 11 +----------
    > fs/jbd2/transaction.c | 14 +++-----------
    > 2 files changed, 4 insertions(+), 21 deletions(-)
    >
    > diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
    > index 1695ba8334a2..bf7474deda2f 100644
    > --- a/fs/jbd/transaction.c
    > +++ b/fs/jbd/transaction.c
    > @@ -673,16 +673,7 @@ do_get_write_access(handle_t *handle, struct journal_head *jh,
    > jbd_unlock_bh_state(bh);
    > frozen_buffer =
    > jbd_alloc(jh2bh(jh)->b_size,
    > - GFP_NOFS);
    > - if (!frozen_buffer) {
    > - printk(KERN_ERR
    > - "%s: OOM for frozen_buffer\n",
    > - __func__);
    > - JBUFFER_TRACE(jh, "oom!");
    > - error = -ENOMEM;
    > - jbd_lock_bh_state(bh);
    > - goto done;
    > - }
    > + GFP_NOFS|__GFP_NOFAIL);
    > goto repeat;
    > }
    > jh->b_frozen_data = frozen_buffer;
    > diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
    > index ff2f2e6ad311..bff071e21553 100644
    > --- a/fs/jbd2/transaction.c
    > +++ b/fs/jbd2/transaction.c
    > @@ -923,16 +923,7 @@ do_get_write_access(handle_t *handle, struct journal_head *jh,
    > jbd_unlock_bh_state(bh);
    > frozen_buffer =
    > jbd2_alloc(jh2bh(jh)->b_size,
    > - GFP_NOFS);
    > - if (!frozen_buffer) {
    > - printk(KERN_ERR
    > - "%s: OOM for frozen_buffer\n",
    > - __func__);
    > - JBUFFER_TRACE(jh, "oom!");
    > - error = -ENOMEM;
    > - jbd_lock_bh_state(bh);
    > - goto done;
    > - }
    > + GFP_NOFS|__GFP_NOFAIL);
    > goto repeat;
    > }
    > jh->b_frozen_data = frozen_buffer;
    > @@ -1157,7 +1148,8 @@ int jbd2_journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
    >
    > repeat:
    > if (!jh->b_committed_data) {
    > - committed_data = jbd2_alloc(jh2bh(jh)->b_size, GFP_NOFS);
    > + committed_data = jbd2_alloc(jh2bh(jh)->b_size,
    > + GFP_NOFS|__GFP_NOFAIL);
    > if (!committed_data) {
    > printk(KERN_ERR "%s: No memory for committed data\n",
    > __func__);

    Is this "if (!committed_data) {" check now dead code?

    I also see other similar suspected dead sites in the rest of the series.


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